<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//NLM//DTD JATS (Z39.96) Journal Publishing DTD v1.1 20151215//EN" "http://jats.nlm.nih.gov/publishing/1.1/JATS-journalpublishing1.dtd">
<article xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en" article-type="research-article" dtd-version="1.1">
<front>
<journal-meta>
<journal-id journal-id-type="pmc">CMC</journal-id>
<journal-id journal-id-type="nlm-ta">CMC</journal-id>
<journal-id journal-id-type="publisher-id">CMC</journal-id>
<journal-title-group>
<journal-title>Computers, Materials &#x0026; Continua</journal-title>
</journal-title-group>
<issn pub-type="epub">1546-2226</issn>
<issn pub-type="ppub">1546-2218</issn>
<publisher>
<publisher-name>Tech Science Press</publisher-name>
<publisher-loc>USA</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="publisher-id">69842</article-id>
<article-id pub-id-type="doi">10.32604/cmc.2025.069842</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Article</subject>
</subj-group>
</article-categories>
<title-group>
<article-title>Prediction of Water Uptake Percentage of Nanoclay-Modified Glass Fiber/Epoxy Composites Using Artificial Neural Network Modelling</article-title>
<alt-title alt-title-type="left-running-head">Prediction of Water Uptake Percentage of Nanoclay-Modified Glass Fiber/Epoxy Composites Using Artificial Neural Network Modelling</alt-title>
<alt-title alt-title-type="right-running-head">Prediction of Water Uptake Percentage of Nanoclay-Modified Glass Fiber/Epoxy Composites Using Artificial Neural Network Modelling</alt-title>
</title-group>
<contrib-group>
<contrib id="author-1" contrib-type="author">
<name name-style="western"><surname>Bhat</surname><given-names>Ashwini</given-names></name><xref ref-type="aff" rid="aff-1">1</xref></contrib>
<contrib id="author-2" contrib-type="author">
<name name-style="western"><surname>Katagi</surname><given-names>Nagaraj N.</given-names></name><xref ref-type="aff" rid="aff-1">1</xref></contrib>
<contrib id="author-3" contrib-type="author">
<name name-style="western"><surname>Gowrishankar</surname><given-names>M. C.</given-names></name><xref ref-type="aff" rid="aff-2">2</xref></contrib>
<contrib id="author-4" contrib-type="author" corresp="yes">
<name name-style="western"><surname>Shettar</surname><given-names>Manjunath</given-names></name><xref ref-type="aff" rid="aff-2">2</xref><email>manjunath.shettar@manipal.edu</email></contrib>
<aff id="aff-1"><label>1</label><institution>Department of Mathematics, Manipal Institute of Technology, Manipal Academy of Higher Education</institution>, <addr-line>Manipal, 576104, Karnataka</addr-line>, <country>India</country></aff>
<aff id="aff-2"><label>2</label><institution>Department of Mechanical and Industrial Engineering, Manipal Institute of Technology, Manipal Academy of Higher Education</institution>, <addr-line>Manipal, 576104, Karnataka</addr-line>, <country>India</country></aff>
</contrib-group>
<author-notes>
<corresp id="cor1"><label>&#x002A;</label>Corresponding Author: Manjunath Shettar. Email: <email>manjunath.shettar@manipal.edu</email></corresp>
</author-notes>
<pub-date date-type="collection" publication-format="electronic">
<year>2025</year></pub-date>
<pub-date date-type="pub" publication-format="electronic">
<day>23</day><month>09</month><year>2025</year></pub-date>
<volume>85</volume>
<issue>2</issue>
<fpage>2715</fpage>
<lpage>2728</lpage>
<history>
<date date-type="received">
<day>01</day>
<month>7</month>
<year>2025</year>
</date>
<date date-type="accepted">
<day>13</day>
<month>8</month>
<year>2025</year>
</date>
</history>
<permissions>
<copyright-statement>&#x00A9; 2025 The Authors.</copyright-statement>
<copyright-year>2025</copyright-year>
<copyright-holder>Published by Tech Science Press.</copyright-holder>
<license xlink:href="https://creativecommons.org/licenses/by/4.0/">
<license-p>This work is licensed under a <ext-link ext-link-type="uri" xlink:type="simple" xlink:href="https://creativecommons.org/licenses/by/4.0/">Creative Commons Attribution 4.0 International License</ext-link>, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.</license-p>
</license>
</permissions>
<self-uri content-type="pdf" xlink:href="TSP_CMC_69842.pdf"></self-uri>
<abstract>
<p>This research explores the water uptake behavior of glass fiber/epoxy composites filled with nanoclay and establishes an Artificial Neural Network (ANN) to predict water uptake percentage from experimental parameters. Composite laminates are fabricated with varying glass fiber <inline-formula id="ieqn-1"><mml:math id="mml-ieqn-1"><mml:mo stretchy="false">(</mml:mo><mml:mn>40</mml:mn><mml:mspace width="negativethinmathspace" /><mml:mo>&#x2212;</mml:mo><mml:mspace width="negativethinmathspace" /><mml:mn>60</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mi mathvariant="normal">&#x0025;</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula> and nanoclay <inline-formula id="ieqn-2"><mml:math id="mml-ieqn-2"><mml:mo stretchy="false">(</mml:mo><mml:mn>0</mml:mn><mml:mspace width="negativethinmathspace" /><mml:mo>&#x2212;</mml:mo><mml:mspace width="negativethinmathspace" /><mml:mn>4</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mi mathvariant="normal">&#x0025;</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula> contents. Water absorption is evaluated for 70 days of immersion following ASTM D570-98 standards. The inclusion of nanoclay reduces water uptake by creating a tortuous path for moisture diffusion due to its high aspect ratio and platelet morphology, thereby enhancing the composite&#x2019;s barrier properties. The ANN model is developed with a 3&#x2013;4&#x2013;1 feedforward structure and learned through the Levenberg&#x2013;Marquardt algorithm with soaking time (7 to 70 days), fiber content <inline-formula id="ieqn-3"><mml:math id="mml-ieqn-3"><mml:mo stretchy="false">(</mml:mo><mml:mn>40</mml:mn><mml:mo>,</mml:mo><mml:mn>50</mml:mn><mml:mo>,</mml:mo><mml:mrow><mml:mtext>&#xA0;and&#xA0;</mml:mtext></mml:mrow><mml:mn>60</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mi mathvariant="normal">&#x0025;</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula> and nanoclay content <inline-formula id="ieqn-4"><mml:math id="mml-ieqn-4"><mml:mo stretchy="false">(</mml:mo><mml:mn>0</mml:mn><mml:mo>,</mml:mo><mml:mn>2</mml:mn><mml:mo>,</mml:mo><mml:mrow><mml:mtext>&#xA0;and&#xA0;</mml:mtext></mml:mrow><mml:mn>4</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mi mathvariant="normal">&#x0025;</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula> as input parameters. The model&#x2019;s output is the water uptake percentage. The model has high prediction efficiency, with a correlation coefficient <inline-formula id="ieqn-5"><mml:math id="mml-ieqn-5"><mml:mo stretchy="false">(</mml:mo><mml:mi>R</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula> of <inline-formula id="ieqn-6"><mml:math id="mml-ieqn-6"><mml:mn>0.998</mml:mn></mml:math></inline-formula> and a mean squared error of <inline-formula id="ieqn-7"><mml:math id="mml-ieqn-7"><mml:mn>1.38</mml:mn><mml:mo>&#x00D7;</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mrow><mml:mo>&#x2212;</mml:mo><mml:mn>4</mml:mn></mml:mrow></mml:msup></mml:math></inline-formula>. Experimental and predicted values are in excellent agreement, ensuring the reliability of the ANN for the simulation of nonlinear water absorption behavior. The results identify the synergistic capability of nanoclay and fiber concentration to reduce water absorption and prove the feasibility of ANN as a substitute for time-consuming testing in composite durability estimation.</p>
</abstract>
<kwd-group kwd-group-type="author">
<kwd>Glass fiber epoxy composites</kwd>
<kwd>nanoclay</kwd>
<kwd>water uptake</kwd>
<kwd>ANN</kwd>
</kwd-group>
</article-meta>
</front>
<body>
<sec id="s1">
<label>1</label>
<title>Introduction</title>
<p>Fiber reinforced polymer composites (FRPCs) are universally accepted in the automotive industry, marine industry, and civil engineering applications because of their high specific strength, stiffness, corrosion resistance, and light weight [<xref ref-type="bibr" rid="ref-1">1</xref>,<xref ref-type="bibr" rid="ref-2">2</xref>]. Compared to composites reinforced with natural or carbon fibers, glass fiber/epoxy composites provide a more favorable balance between mechanical performance, cost, and environmental durability, making them well-suited for structural applications in the marine and aerospace sectors. Though their short-term performance is satisfactory, long-term performance degrades when subjected to environmental conditions like water, humidity, thermal cycling, and chemical attack. This calls for material modifications and predictive modelling tools to improve performance and predict behavior in service. Water absorption is a critical degradation mechanism in fiber-reinforced polymer composites, leading to plasticization of the matrix, fiber&#x2013;matrix debonding, and long-term mechanical property deterioration. Even moderate moisture ingress can lead to dimensional instability, reduced load-bearing capacity, and premature failure in marine, civil infrastructure, and transportation sectors. Therefore, quantifying and predicting water uptake behavior is essential for ensuring structural reliability and longevity [<xref ref-type="bibr" rid="ref-3">3</xref>,<xref ref-type="bibr" rid="ref-4">4</xref>].</p>
<p>Over the past few years, advances in nanotechnology have made it possible to utilize nanofillers to design the properties of polymer composites. Among numerous nanofillers, layered silicate-based nanoclay has emerged as a promising nanofiller capable of improving epoxy matrices&#x2019; mechanical, thermal, and barrier performances [<xref ref-type="bibr" rid="ref-5">5</xref>&#x2013;<xref ref-type="bibr" rid="ref-7">7</xref>]. The platelet nature and high aspect ratio of nanoclay help enhance load transfer, decrease moisture permeability, and delay crack propagation [<xref ref-type="bibr" rid="ref-8">8</xref>]. Some studies have shown that adding nanoclay to epoxy/glass fiber composites improves tensile strength, interlaminar shear strength, and hygrothermal aging resistance [<xref ref-type="bibr" rid="ref-9">9</xref>,<xref ref-type="bibr" rid="ref-10">10</xref>]. However, the efficacy of nanoclay reinforcement is influenced significantly by dispersion quality, filler loading, and fiber&#x2013;matrix interface interaction.</p>
<p>Traditional experimental methods to measure the effect of nanofillers on composite properties are time-consuming, labor-intensive, and material-intensive. In addition, it is challenging for conventional statistical models to predict the nonlinear impact of multiple factors, filler content, environmental exposure, and processing conditions [<xref ref-type="bibr" rid="ref-11">11</xref>,<xref ref-type="bibr" rid="ref-12">12</xref>]. Artificial Neural Networks (ANNs) are powerful tools for modelling complex multivariable systems, especially in material science, where fabrication parameter dependence of performance properties is strongly nonlinear. ANNs are computer models inspired by the brain&#x2019;s operation that can learn complex input-output mappings without direct physical models [<xref ref-type="bibr" rid="ref-13">13</xref>].</p>
<p>ANNs are successfully employed in composite materials to simulate mechanical strength, water absorption, and wear resistance due to fabrication and material characteristics [<xref ref-type="bibr" rid="ref-14">14</xref>,<xref ref-type="bibr" rid="ref-15">15</xref>]. ANNs are distinct from regression models as they can handle nonlinearities and interactions between multiple variables. They are best-suited for systems with complex input&#x2013;output behavior, such as nanocomposites.</p>
<p>The study by Y&#x0131;ld&#x0131;r&#x0131;m [<xref ref-type="bibr" rid="ref-16">16</xref>] focuses on using an ANN to accurately predict how the weight of glass fiber-reinforced polymer composites filled with SiC nanoparticles changes during artificial aging. The ANN model is developed using MATLAB with a (2-4-1) architecture and is trained using the Levenberg&#x2013;Marquardt algorithm. It uses nanoparticle weight percentage and aging time as input parameters. The model achieves high prediction accuracy, with a low mean square error of <inline-formula id="ieqn-8"><mml:math id="mml-ieqn-8"><mml:mn>0.001225</mml:mn></mml:math></inline-formula> and a strong correlation coefficient <inline-formula id="ieqn-9"><mml:math id="mml-ieqn-9"><mml:mo stretchy="false">(</mml:mo><mml:mi>R</mml:mi><mml:mo>=</mml:mo><mml:mn>0.99385</mml:mn><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula>. ANN outperforms traditional models in handling complex, nonlinear data and reduces the need for extensive experimental testing. The study highlights the potential of ANN as an effective tool for simulating material behavior, optimizing composite design, and minimizing both time and cost in materials science.</p>
<p>Similarly, Capiel et al. [<xref ref-type="bibr" rid="ref-17">17</xref>] design ANN models to predict water absorption in glass fiber-reinforced nanoclay-epoxy composites. Two models are constructed for modified and unmodified bentonite systems. With a three-input (bentonite content, temperature, and immersion time) and one-output (water absorption) architecture with two hidden layers, the networks are trained with the Levenberg&#x2013;Marquardt algorithm. With over 4600 experimental data points, both models performed exceptionally well regarding predictive capability, with correlation coefficients <inline-formula id="ieqn-10"><mml:math id="mml-ieqn-10"><mml:mo stretchy="false">(</mml:mo><mml:msup><mml:mi>R</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula> of over <inline-formula id="ieqn-11"><mml:math id="mml-ieqn-11"><mml:mn>0.96</mml:mn></mml:math></inline-formula>. The two models produce reliable water uptake behavior mapping over time and temperature regimes, enabling the prediction of critical degradation points under service conditions.</p>
<p>In a related study, Saaidia et al. [<xref ref-type="bibr" rid="ref-18">18</xref>] apply ANN to model water absorption in jute and sisal fiber-reinforced epoxy composites with varying lengths of the fibers (5, 10, and 15 mm). The Levenberg&#x2013;Marquardt algorithm-trained ANN accurately models the saturation kinetic curve of water absorption. The study emphasizes the capability of ANN in optimizing such critical parameters as immersion time and fiber length with reduced reliance on experimental analysis.</p>
<p>Likewise, Makhlouf et al. [<xref ref-type="bibr" rid="ref-19">19</xref>] use ANN modelling to simulate water absorption in HDPE/jute fiber biocomposites. The model with input parameters of fiber loading and immersion time, and output as water absorption, has an excellent correlation between simulated and experimental data (<inline-formula id="ieqn-12"><mml:math id="mml-ieqn-12"><mml:mo stretchy="false">(</mml:mo><mml:msup><mml:mi>R</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula> of almost 1).</p>
<p>While prior studies have implemented ANN for predicting mechanical strength [<xref ref-type="bibr" rid="ref-14">14</xref>], wear resistance [<xref ref-type="bibr" rid="ref-15">15</xref>], and even water absorption [<xref ref-type="bibr" rid="ref-16">16</xref>&#x2013;<xref ref-type="bibr" rid="ref-19">19</xref>], most models have focused on fixed fiber or filler types and used limited input variables. Y&#x0131;ld&#x0131;r&#x0131;m [<xref ref-type="bibr" rid="ref-16">16</xref>] has used a 2-input ANN model to simulate SiC nanoparticle-filled composites, and Capiel et al. [<xref ref-type="bibr" rid="ref-17">17</xref>] have modeled water uptake in nanoclay-epoxy systems without varying the reinforcement. However, composite water absorption is influenced by complex, nonlinear interactions between fiber content, filler dispersion, and soaking time. This study addresses that gap by developing a multi-input ANN model trained on experimentally validated fiber and nanoclay content combinations across immersion durations, thereby capturing synergistic effects that earlier studies have not explored.</p>
<p>This study&#x2019;s novelty lies in developing an ANN-based predictive model for water uptake in a hybrid composite system combining varying glass fiber contents with nanoclay-modified epoxy resin. Unlike earlier models that focused solely on natural fibers, single fillers, or fixed reinforcement levels, this work explores the combined influence of fiber loading and nanoclay concentration across multiple immersion durations. Using a tailored feedforward ANN architecture (3-4-1) with input variables of soaking time, glass fiber wt.%, and nanoclay wt.% allows for accurate modelling of the nonlinear moisture absorption behavior. Furthermore, including intermediate confirmation tests not present in the training set demonstrates the model&#x2019;s strong interpolation capability and generalization strength. This integrated approach offers a cost-effective and accurate alternative to prolonged experimentation, advancing composite design strategies for enhanced hydrothermal durability.</p>
</sec>
<sec id="s2">
<label>2</label>
<title>Methodology</title>
<sec id="s2_1">
<label>2.1</label>
<title>Materials and Preparation of Composites</title>
<p>Epoxy resin (L-12) and hardener (K-6) are sourced from Atul Polymers, Gujarat, India, while the bi-directional woven E-glass fabric is obtained from Yuje Enterprises, Bengaluru. The surface-modified nanoclay, containing <inline-formula id="ieqn-13"><mml:math id="mml-ieqn-13"><mml:mo stretchy="false">(</mml:mo><mml:mn>25</mml:mn><mml:mspace width="negativethinmathspace" /><mml:mo>&#x2212;</mml:mo><mml:mspace width="negativethinmathspace" /><mml:mn>30</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula> trimethyl stearyl ammonium, is purchased from Sigma Aldrich. Selected material properties used in this study are shown in <xref ref-type="table" rid="table-1">Table 1</xref>.</p>
<table-wrap id="table-1">
<label>Table 1</label>
<caption>
<title>Properties of selected material</title>
</caption>
<table>
<colgroup>
<col align="center"/>
<col align="center"/>
<col align="center"/>
</colgroup>
<thead>
<tr>
<th align="center">Sl. No.</th>
<th align="center">Material name</th>
<th align="center">Properties</th>
</tr>
</thead>
<tbody>
<tr>
<td rowspan="4">1</td>
<td rowspan="4">Epoxy resin (L-12) and hardener (K-6)</td>
<td>Tensile strength (MPa)&#x2014;55&#x2013;70</td>
</tr>
<tr>

<td>Tensile modulus (GPa)&#x2014;2.5&#x2013;4</td>
</tr>
<tr>

<td>Flexural strength (MPa)&#x2014;120&#x2013;140</td>
</tr>
<tr>

<td>Density (g/cm<sup>3</sup>)&#x2014;1.15</td>
</tr>
<tr>
<td rowspan="5">2</td>
<td rowspan="5">Nanoclay (Montmorillonite (MMT))</td>
<td>Appearance (color)&#x2014;White to off-white</td>
</tr>
<tr>

<td>Appearance (form)&#x2014;Powder</td>
</tr>
<tr>

<td>Size&#x2014;&#x003C;20 &#x00B5;m</td>
</tr>
<tr>

<td>Bulk density&#x2014;200&#x2013;500 kg/m<sup>3</sup></td>
</tr>
<tr>

<td>Surface modified contains 15&#x2013;35 wt.% octadecylamine, 0.5&#x2013;5 wt.% aminopropyltriethoxysilane.</td>
</tr>
<tr>
<td rowspan="3">3</td>
<td rowspan="3">Glass fiber</td>
<td>Tensile strength (MPa)&#x2014;1720&#x2013;1950</td>
</tr>
<tr>

<td>Tensile modulus (GPa)&#x2014;72&#x2013;76</td>
</tr>
<tr>

<td>Density (g/cm<sup>3</sup>)&#x2014;2.5</td>
</tr>
</tbody>
</table>
</table-wrap>
<p>Nanoclay is mixed into the epoxy using a magnetic stirrer for <inline-formula id="ieqn-14"><mml:math id="mml-ieqn-14"><mml:mn>30</mml:mn><mml:mspace width="thinmathspace" /><mml:mo movablelimits="true" form="prefix">min</mml:mo></mml:math></inline-formula>, followed by sonication for 2<inline-formula id="ieqn-15"><mml:math id="mml-ieqn-15"><mml:mn>0</mml:mn><mml:mspace width="thinmathspace" /><mml:mo movablelimits="true" form="prefix">min</mml:mo></mml:math></inline-formula>. The resulting nanoclay-epoxy blend is then combined thoroughly with the hardener. Laminates containing varying amounts of glass fiber <inline-formula id="ieqn-16"><mml:math id="mml-ieqn-16"><mml:mo stretchy="false">(</mml:mo><mml:mn>40</mml:mn><mml:mo>,</mml:mo><mml:mn>50</mml:mn><mml:mo>,</mml:mo><mml:mrow><mml:mtext>&#xA0;and&#xA0;</mml:mtext></mml:mrow><mml:mn>60</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula> and nanoclay <inline-formula id="ieqn-17"><mml:math id="mml-ieqn-17"><mml:mo stretchy="false">(</mml:mo><mml:mn>0</mml:mn><mml:mo>,</mml:mo><mml:mn>2</mml:mn><mml:mo>,</mml:mo><mml:mrow><mml:mtext>&#xA0;and&#xA0;</mml:mtext></mml:mrow><mml:mn>4</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula> are fabricated using the hand lay-up method followed by compression molding. A roller is applied over the wet layers to eliminate trapped air and ensure uniform consolidation, starting from the center and moving outward. The compression molding process is performed under <inline-formula id="ieqn-18"><mml:math id="mml-ieqn-18"><mml:mn>100</mml:mn><mml:mrow><mml:mtext>&#xA0;bar</mml:mtext></mml:mrow></mml:math></inline-formula> pressure at <inline-formula id="ieqn-19"><mml:math id="mml-ieqn-19"><mml:msup><mml:mn>50</mml:mn><mml:mrow><mml:mo>&#x2218;</mml:mo></mml:mrow></mml:msup><mml:mrow><mml:mtext>C</mml:mtext></mml:mrow></mml:math></inline-formula> for <inline-formula id="ieqn-20"><mml:math id="mml-ieqn-20"><mml:mn>24</mml:mn><mml:mrow><mml:mtext>h</mml:mtext></mml:mrow></mml:math></inline-formula>. Final laminate dimensions are maintained at <inline-formula id="ieqn-21"><mml:math id="mml-ieqn-21"><mml:mn>300</mml:mn><mml:mrow><mml:mtext>&#xA0;mm&#xA0;</mml:mtext></mml:mrow><mml:mo>&#x00D7;</mml:mo><mml:mn>300</mml:mn><mml:mrow><mml:mtext>&#xA0;mm&#xA0;</mml:mtext></mml:mrow><mml:mo>&#x00D7;</mml:mo><mml:mn>3</mml:mn><mml:mrow><mml:mtext>&#xA0;mm</mml:mtext></mml:mrow></mml:math></inline-formula>, with a <inline-formula id="ieqn-22"><mml:math id="mml-ieqn-22"><mml:mn>1</mml:mn><mml:mi mathvariant="normal">&#x0025;</mml:mi></mml:math></inline-formula> bilateral tolerance in volume. A stopper ensured a consistent laminate thickness of <inline-formula id="ieqn-23"><mml:math id="mml-ieqn-23"><mml:mn>3</mml:mn><mml:mrow><mml:mtext>&#xA0;mm</mml:mtext></mml:mrow></mml:math></inline-formula>. The specific procedures for composite laminate preparation are detailed in <xref ref-type="fig" rid="fig-1">Fig. 1</xref>. <xref ref-type="table" rid="table-2">Table 2</xref> presents the weight percentage details of constituents for <inline-formula id="ieqn-24"><mml:math id="mml-ieqn-24"><mml:mn>50</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> glass fiber reinforced composites. The glass fiber weight fraction is precisely controlled using analytical weighing <inline-formula id="ieqn-25"><mml:math id="mml-ieqn-25"><mml:mo>&#x00B1;</mml:mo><mml:mn>0.01</mml:mn><mml:mrow><mml:mtext>g</mml:mtext></mml:mrow></mml:math></inline-formula>. Careful layering during hand lay-up ensures consistent distribution across the laminate surface.</p>
<fig id="fig-1">
<label>Figure 1</label>
<caption>
<title>Preparation of composite laminates</title>
</caption>
<graphic mimetype="image" mime-subtype="tif" xlink:href="CMC_69842-fig-1.tif"/>
</fig><table-wrap id="table-2">
<label>Table 2</label>
<caption>
<title>Weight percentage details of constituents for <inline-formula id="ieqn-26"><mml:math id="mml-ieqn-26"><mml:mn>50</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> glass fibre reinforced composites</title>
</caption>
<table>
<colgroup>
<col/>
<col/>
<col/>
<col/>
<col/>
<col/>
<col/>
</colgroup>
<thead>
<tr>
<th></th>
<th>Wt.%</th>
<th>Wt. (g)</th>
<th>Wt.%</th>
<th>Wt. (g)</th>
<th>Wt.%</th>
<th>Wt. (g)</th>
</tr>
</thead>
<tbody>
<tr>
<td>Glass fiber</td>
<td>50</td>
<td>235</td>
<td>50</td>
<td>235</td>
<td>50</td>
<td>235</td>
</tr>
<tr>
<td>Epoxy</td>
<td>50</td>
<td>235</td>
<td>48</td>
<td>225.6</td>
<td>46</td>
<td>216.2</td>
</tr>
<tr>
<td>Nanoclay</td>
<td>0</td>
<td>0</td>
<td>2</td>
<td>9.4</td>
<td>4</td>
<td>18.8</td>
</tr>
<tr>
<td>Total</td>
<td>100</td>
<td>470</td>
<td>100</td>
<td>470</td>
<td>100</td>
<td>470</td>
</tr>
</tbody>
</table>
</table-wrap>
</sec>
<sec id="s2_2">
<label>2.2</label>
<title>Water Uptake</title>
<p>Water uptake tests are conducted following ASTM D570-98 standards. Initially, the dry sample weight of each specimen is recorded using a digital weighing machine. The samples are then immersed in tap water at room temperature (<inline-formula id="ieqn-27"><mml:math id="mml-ieqn-27"><mml:msup><mml:mn>25</mml:mn><mml:mrow><mml:mo>&#x2218;</mml:mo></mml:mrow></mml:msup><mml:mrow><mml:mtext>C</mml:mtext></mml:mrow></mml:math></inline-formula>) for a duration of <inline-formula id="ieqn-28"><mml:math id="mml-ieqn-28"><mml:mn>70</mml:mn></mml:math></inline-formula> days. Five specimens of each type of composite are immersed. The specimens are taken out at weekly intervals, gently wiped with a clean cloth to remove surface moisture, and weighed again. The water uptake (%) is calculated based on the change in mass over the measured time periods. The water uptake percentage is determined by:<disp-formula id="ueqn-1"><mml:math id="mml-ueqn-1" display="block"><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow><mml:mrow><mml:mtext>of water uptake&#xA0;</mml:mtext></mml:mrow><mml:mo>=</mml:mo><mml:mfrac><mml:mrow><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:mtext>Wa</mml:mtext></mml:mrow><mml:mo>&#x2212;</mml:mo><mml:mrow><mml:mtext>Wd</mml:mtext></mml:mrow><mml:mo>)</mml:mo></mml:mrow><mml:mo mathvariant="bold">&#x00D7;</mml:mo><mml:mn>100</mml:mn></mml:mrow><mml:mrow><mml:mtext>Wd</mml:mtext></mml:mrow></mml:mfrac></mml:math></disp-formula>where, Wa&#x2014;weight of the specimen after absorption, Wd&#x2014;Weight of the dry specimen</p>
</sec>
<sec id="s2_3">
<label>2.3</label>
<title>Artificial Neural Network (ANN) Modelling</title>
<p>This work develops an ANN-based predictive model to estimate the water uptake percentage of glass fiber/epoxy composites modified with nanoclay under various soaking durations.</p>
<sec id="s2_3_1">
<label>2.3.1</label>
<title>Network Design</title>
<p>The ANN architecture is selected based on preliminary trials to balance model simplicity and prediction accuracy. The optimal structure consists of
<list list-type="simple">
<list-item><label>a.</label>
<p>Three input nodes, corresponding to soaking time (days), glass fiber content (wt.%), and nanoclay content (wt.%).</p></list-item>
<list-item><label>b.</label>
<p>One hidden layer with four neurons, a structure chosen after iterative tuning to avoid underfitting and overfitting. The final ANN architecture (3-4-1) is selected after a manual grid search, trialing different hidden layers (1-3) and neurons (2-6). The (3-4-1) model shows optimal performance in terms of MSE and training stability.</p></list-item>
<list-item><label>c.</label>
<p>One output node, representing the predicted water uptake (%).</p></list-item>
</list></p>
</sec>
<sec id="s2_3_2">
<label>2.3.2</label>
<title>Transfer Functions and Learning Algorithm</title>
<p>The hidden layer utilizes a <italic>tansig</italic> (hyperbolic tangent sigmoid) function, effectively mapping nonlinear relationships between inputs and outputs in the range of <inline-formula id="ieqn-29"><mml:math id="mml-ieqn-29"><mml:mrow><mml:mo>[</mml:mo><mml:mo>&#x2212;</mml:mo><mml:mn>1</mml:mn><mml:mo>,</mml:mo><mml:mo>+</mml:mo><mml:mn>1</mml:mn><mml:mo>]</mml:mo></mml:mrow><mml:mo>.</mml:mo></mml:math></inline-formula> The output layer employs a <italic>purelin</italic> (linear) function to predict the continuous water uptake percentage value. The training is conducted using the Levenberg&#x2013;Marquardt (trainlm) algorithm, selected for its superior convergence speed and stability for function-fitting problems with moderate-sized datasets [<xref ref-type="bibr" rid="ref-20">20</xref>].</p>
</sec>
<sec id="s2_3_3">
<label>2.3.3</label>
<title>Training Strategy and Data Management</title>
<p>The available data set is partitioned into <inline-formula id="ieqn-30"><mml:math id="mml-ieqn-30"><mml:mn>70</mml:mn><mml:mi mathvariant="normal">&#x0025;</mml:mi></mml:math></inline-formula> for training, <inline-formula id="ieqn-31"><mml:math id="mml-ieqn-31"><mml:mn>15</mml:mn><mml:mi mathvariant="normal">&#x0025;</mml:mi></mml:math></inline-formula> for validation, and <inline-formula id="ieqn-32"><mml:math id="mml-ieqn-32"><mml:mn>15</mml:mn><mml:mi mathvariant="normal">&#x0025;</mml:mi></mml:math></inline-formula> for testing. Data normalization is applied prior to training to improve convergence, transforming input variables to a normalized scale suitable for the <italic>tansig</italic> functions. Multiple initializations with random weights are performed to avoid local minima, and the best-performing network (based on minimal validation error) is selected.</p>
</sec>
<sec id="s2_3_4">
<label>2.3.4</label>
<title>Model Evaluation Metrics</title>
<p>The model&#x2019;s learning performance is assisted through Mean Squared Error (MSE), the Regression coefficient <inline-formula id="ieqn-33"><mml:math id="mml-ieqn-33"><mml:mrow><mml:mo>(</mml:mo><mml:mi>R</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:math></inline-formula>, gradient, and mu behavior, which is indicative of training stability. The ANN&#x2019;s final architecture and hyperparameters are detailed in <xref ref-type="table" rid="table-3">Table 3</xref>, and the network structure is visualized in <xref ref-type="fig" rid="fig-2">Fig. 2</xref>.</p>
<table-wrap id="table-3">
<label>Table 3</label>
<caption>
<title>The ANN training parameters</title>
</caption>
<table>
<colgroup>
<col/>
<col/>
</colgroup>
<thead>
<tr>
<th>Parameter</th>
<th>Value</th>
</tr>
</thead>
<tbody>
<tr>
<td>Hidden neurons</td>
<td>4</td>
</tr>
<tr>
<td>Training algorithm</td>
<td>Levenberg&#x2013;Marquardt (trainlm)</td>
</tr>
<tr>
<td>Learning rate</td>
<td>0.4</td>
</tr>
<tr>
<td>Momentum constant</td>
<td>0.9</td>
</tr>
<tr>
<td>Performance goal</td>
<td>0.00001</td>
</tr>
<tr>
<td>Epoch limit</td>
<td>1000</td>
</tr>
</tbody>
</table>
</table-wrap><fig id="fig-2">
<label>Figure 2</label>
<caption>
<title>Architecture of the developed ANN model for water uptake prediction</title>
</caption>
<graphic mimetype="image" mime-subtype="tif" xlink:href="CMC_69842-fig-2.tif"/>
</fig>
</sec>
</sec>
</sec>
<sec id="s3">
<label>3</label>
<title>Results and Discussion</title>
<sec id="s3_1">
<label>3.1</label>
<title>Water Uptake (%)</title>
<p><xref ref-type="table" rid="table-4">Table 4</xref> illustrates the water uptake behavior of glass fiber reinforced epoxy composites modified with varying nanoclay content over an immersion period of <inline-formula id="ieqn-34"><mml:math id="mml-ieqn-34"><mml:mn>70</mml:mn></mml:math></inline-formula> days. Water absorption increases steadily with immersion duration for all composite formulations. The uptake rate is initially high during the early days due to the steep concentration gradient between the dry composite and the surrounding water. This gradually slows, approaching near-equilibrium by day <inline-formula id="ieqn-35"><mml:math id="mml-ieqn-35"><mml:mn>70</mml:mn></mml:math></inline-formula>, indicating a saturation behavior characteristic of Fickian diffusion [<xref ref-type="bibr" rid="ref-21">21</xref>]. The saturation of water uptake beyond <inline-formula id="ieqn-36"><mml:math id="mml-ieqn-36"><mml:mn>63</mml:mn><mml:mspace width="negativethinmathspace" /><mml:mo>&#x2212;</mml:mo><mml:mspace width="negativethinmathspace" /><mml:mn>70</mml:mn></mml:math></inline-formula> days signifies that most of the accessible voids and hydrophilic regions in the matrix are filled.</p>
<table-wrap id="table-4">
<label>Table 4</label>
<caption>
<title>Water uptake (%) for different composites</title>
</caption>
<table>
<colgroup>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
</colgroup>
<thead>
<tr>
<th align="center">Sl. No.</th>
<th align="center">Days</th>
<th align="center">Glass fiber (wt.%)</th>
<th align="center">Nanoclay (wt.%)</th>
<th align="center">Water uptake (%)</th>
<th align="center">Sl. No.</th>
<th align="center">Days</th>
<th align="center">Glass fiber (wt.%)</th>
<th align="center">Nanoclay (wt.%)</th>
<th align="center">Water uptake (%)</th>
<th align="center">Sl. No.</th>
<th align="center">Days</th>
<th align="center">Glass fiber (wt.%)</th>
<th align="center">Nanoclay (wt.%)</th>
<th align="center">Water uptake (%)</th>
</tr>
</thead>
<tbody>
<tr>
<td><bold>1</bold></td>
<td>7</td>
<td>40</td>
<td>0</td>
<td>0.3</td>
<td><bold>31</bold></td>
<td>7</td>
<td>50</td>
<td>0</td>
<td>0.27</td>
<td><bold>61</bold></td>
<td>7</td>
<td>60</td>
<td>0</td>
<td>0.25</td>
</tr>
<tr>
<td><bold>2</bold></td>
<td>14</td>
<td>40</td>
<td>0</td>
<td>0.46</td>
<td><bold>32</bold></td>
<td>14</td>
<td>50</td>
<td>0</td>
<td>0.44</td>
<td><bold>62</bold></td>
<td>14</td>
<td>60</td>
<td>0</td>
<td>0.41</td>
</tr>
<tr>
<td><bold>3</bold></td>
<td>21</td>
<td>40</td>
<td>0</td>
<td>0.55</td>
<td><bold>33</bold></td>
<td>21</td>
<td>50</td>
<td>0</td>
<td>0.53</td>
<td><bold>63</bold></td>
<td>21</td>
<td>60</td>
<td>0</td>
<td>0.5</td>
</tr>
<tr>
<td><bold>4</bold></td>
<td>28</td>
<td>40</td>
<td>0</td>
<td>0.62</td>
<td><bold>34</bold></td>
<td>28</td>
<td>50</td>
<td>0</td>
<td>0.6</td>
<td><bold>64</bold></td>
<td>28</td>
<td>60</td>
<td>0</td>
<td>0.57</td>
</tr>
<tr>
<td><bold>5</bold></td>
<td>35</td>
<td>40</td>
<td>0</td>
<td>0.66</td>
<td><bold>35</bold></td>
<td>35</td>
<td>50</td>
<td>0</td>
<td>0.64</td>
<td><bold>65</bold></td>
<td>35</td>
<td>60</td>
<td>0</td>
<td>0.61</td>
</tr>
<tr>
<td><bold>6</bold></td>
<td>42</td>
<td>40</td>
<td>0</td>
<td>0.7</td>
<td><bold>36</bold></td>
<td>42</td>
<td>50</td>
<td>0</td>
<td>0.68</td>
<td><bold>66</bold></td>
<td>42</td>
<td>60</td>
<td>0</td>
<td>0.65</td>
</tr>
<tr>
<td><bold>7</bold></td>
<td>49</td>
<td>40</td>
<td>0</td>
<td>0.72</td>
<td><bold>37</bold></td>
<td>49</td>
<td>50</td>
<td>0</td>
<td>0.7</td>
<td><bold>67</bold></td>
<td>49</td>
<td>60</td>
<td>0</td>
<td>0.67</td>
</tr>
<tr>
<td><bold>8</bold></td>
<td>56</td>
<td>40</td>
<td>0</td>
<td>0.73</td>
<td><bold>38</bold></td>
<td>56</td>
<td>50</td>
<td>0</td>
<td>0.71</td>
<td><bold>68</bold></td>
<td>56</td>
<td>60</td>
<td>0</td>
<td>0.68</td>
</tr>
<tr>
<td><bold>9</bold></td>
<td>63</td>
<td>40</td>
<td>0</td>
<td>0.74</td>
<td><bold>39</bold></td>
<td>63</td>
<td>50</td>
<td>0</td>
<td>0.72</td>
<td><bold>69</bold></td>
<td>63</td>
<td>60</td>
<td>0</td>
<td>0.69</td>
</tr>
<tr>
<td><bold>10</bold></td>
<td>70</td>
<td>40</td>
<td>0</td>
<td>0.75</td>
<td><bold>40</bold></td>
<td>70</td>
<td>50</td>
<td>0</td>
<td>0.73</td>
<td><bold>70</bold></td>
<td>70</td>
<td>60</td>
<td>0</td>
<td>0.7</td>
</tr>
<tr>
<td><bold>11</bold></td>
<td>7</td>
<td>40</td>
<td>2</td>
<td>0.27</td>
<td><bold>41</bold></td>
<td>7</td>
<td>50</td>
<td>2</td>
<td>0.24</td>
<td><bold>71</bold></td>
<td>7</td>
<td>60</td>
<td>2</td>
<td>0.22</td>
</tr>
<tr>
<td><bold>12</bold></td>
<td>14</td>
<td>40</td>
<td>2</td>
<td>0.42</td>
<td><bold>42</bold></td>
<td>14</td>
<td>50</td>
<td>2</td>
<td>0.39</td>
<td><bold>72</bold></td>
<td>14</td>
<td>60</td>
<td>2</td>
<td>0.37</td>
</tr>
<tr>
<td><bold>13</bold></td>
<td>21</td>
<td>40</td>
<td>2</td>
<td>0.5</td>
<td><bold>43</bold></td>
<td>21</td>
<td>50</td>
<td>2</td>
<td>0.48</td>
<td><bold>73</bold></td>
<td>21</td>
<td>60</td>
<td>2</td>
<td>0.45</td>
</tr>
<tr>
<td><bold>14</bold></td>
<td>28</td>
<td>40</td>
<td>2</td>
<td>0.56</td>
<td><bold>44</bold></td>
<td>28</td>
<td>50</td>
<td>2</td>
<td>0.54</td>
<td><bold>74</bold></td>
<td>28</td>
<td>60</td>
<td>2</td>
<td>0.51</td>
</tr>
<tr>
<td><bold>15</bold></td>
<td>35</td>
<td>40</td>
<td>2</td>
<td>0.62</td>
<td><bold>45</bold></td>
<td>35</td>
<td>50</td>
<td>2</td>
<td>0.6</td>
<td><bold>75</bold></td>
<td>35</td>
<td>60</td>
<td>2</td>
<td>0.57</td>
</tr>
<tr>
<td><bold>16</bold></td>
<td>42</td>
<td>40</td>
<td>2</td>
<td>0.66</td>
<td><bold>46</bold></td>
<td>42</td>
<td>50</td>
<td>2</td>
<td>0.64</td>
<td><bold>76</bold></td>
<td>42</td>
<td>60</td>
<td>2</td>
<td>0.61</td>
</tr>
<tr>
<td><bold>17</bold></td>
<td>49</td>
<td>40</td>
<td>2</td>
<td>0.68</td>
<td><bold>47</bold></td>
<td>49</td>
<td>50</td>
<td>2</td>
<td>0.66</td>
<td><bold>77</bold></td>
<td>49</td>
<td>60</td>
<td>2</td>
<td>0.63</td>
</tr>
<tr>
<td><bold>18</bold></td>
<td>56</td>
<td>40</td>
<td>2</td>
<td>0.69</td>
<td><bold>48</bold></td>
<td>56</td>
<td>50</td>
<td>2</td>
<td>0.67</td>
<td><bold>78</bold></td>
<td>56</td>
<td>60</td>
<td>2</td>
<td>0.64</td>
</tr>
<tr>
<td><bold>19</bold></td>
<td>63</td>
<td>40</td>
<td>2</td>
<td>0.7</td>
<td><bold>49</bold></td>
<td>63</td>
<td>50</td>
<td>2</td>
<td>0.68</td>
<td><bold>79</bold></td>
<td>63</td>
<td>60</td>
<td>2</td>
<td>0.65</td>
</tr>
<tr>
<td><bold>20</bold></td>
<td>70</td>
<td>40</td>
<td>2</td>
<td>0.71</td>
<td><bold>50</bold></td>
<td>70</td>
<td>50</td>
<td>2</td>
<td>0.69</td>
<td><bold>80</bold></td>
<td>70</td>
<td>60</td>
<td>2</td>
<td>0.66</td>
</tr>
<tr>
<td><bold>21</bold></td>
<td>7</td>
<td>40</td>
<td>4</td>
<td>0.24</td>
<td><bold>51</bold></td>
<td>7</td>
<td>50</td>
<td>4</td>
<td>0.21</td>
<td><bold>81</bold></td>
<td>7</td>
<td>60</td>
<td>4</td>
<td>0.19</td>
</tr>
<tr>
<td><bold>22</bold></td>
<td>14</td>
<td>40</td>
<td>4</td>
<td>0.38</td>
<td><bold>52</bold></td>
<td>14</td>
<td>50</td>
<td>4</td>
<td>0.35</td>
<td><bold>82</bold></td>
<td>14</td>
<td>60</td>
<td>4</td>
<td>0.33</td>
</tr>
<tr>
<td><bold>23</bold></td>
<td>21</td>
<td>40</td>
<td>4</td>
<td>0.45</td>
<td><bold>53</bold></td>
<td>21</td>
<td>50</td>
<td>4</td>
<td>0.43</td>
<td><bold>83</bold></td>
<td>21</td>
<td>60</td>
<td>4</td>
<td>0.4</td>
</tr>
<tr>
<td><bold>24</bold></td>
<td>28</td>
<td>40</td>
<td>4</td>
<td>0.5</td>
<td><bold>54</bold></td>
<td>28</td>
<td>50</td>
<td>4</td>
<td>0.48</td>
<td><bold>84</bold></td>
<td>28</td>
<td>60</td>
<td>4</td>
<td>0.45</td>
</tr>
<tr>
<td><bold>25</bold></td>
<td>35</td>
<td>40</td>
<td>4</td>
<td>0.58</td>
<td><bold>55</bold></td>
<td>35</td>
<td>50</td>
<td>4</td>
<td>0.56</td>
<td><bold>85</bold></td>
<td>35</td>
<td>60</td>
<td>4</td>
<td>0.53</td>
</tr>
<tr>
<td><bold>26</bold></td>
<td>42</td>
<td>40</td>
<td>4</td>
<td>0.62</td>
<td><bold>56</bold></td>
<td>42</td>
<td>50</td>
<td>4</td>
<td>0.6</td>
<td><bold>86</bold></td>
<td>42</td>
<td>60</td>
<td>4</td>
<td>0.57</td>
</tr>
<tr>
<td><bold>27</bold></td>
<td>49</td>
<td>40</td>
<td>4</td>
<td>0.64</td>
<td><bold>57</bold></td>
<td>49</td>
<td>50</td>
<td>4</td>
<td>0.62</td>
<td><bold>87</bold></td>
<td>49</td>
<td>60</td>
<td>4</td>
<td>0.59</td>
</tr>
<tr>
<td><bold>28</bold></td>
<td>56</td>
<td>40</td>
<td>4</td>
<td>0.65</td>
<td><bold>58</bold></td>
<td>56</td>
<td>50</td>
<td>4</td>
<td>0.63</td>
<td><bold>88</bold></td>
<td>56</td>
<td>60</td>
<td>4</td>
<td>0.6</td>
</tr>
<tr>
<td><bold>29</bold></td>
<td>63</td>
<td>40</td>
<td>4</td>
<td>0.66</td>
<td><bold>59</bold></td>
<td>63</td>
<td>50</td>
<td>4</td>
<td>0.64</td>
<td><bold>89</bold></td>
<td>63</td>
<td>60</td>
<td>4</td>
<td>0.61</td>
</tr>
<tr>
<td><bold>30</bold></td>
<td>70</td>
<td>40</td>
<td>4</td>
<td>0.67</td>
<td><bold>60</bold></td>
<td>70</td>
<td>50</td>
<td>4</td>
<td>0.65</td>
<td><bold>90</bold></td>
<td>70</td>
<td>60</td>
<td>4</td>
<td>0.62</td>
</tr>
</tbody>
</table>
</table-wrap>
<p>A comparison across glass fiber content at constant nanoclay levels reveals that increasing the glass fiber wt.% results in redcution in water uptake percentage. For instance, composites with <inline-formula id="ieqn-37"><mml:math id="mml-ieqn-37"><mml:mn>40</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> glass fiber and no nanoclay show the highest water uptake at <inline-formula id="ieqn-38"><mml:math id="mml-ieqn-38"><mml:mn>0.75</mml:mn><mml:mi mathvariant="normal">&#x0025;</mml:mi></mml:math></inline-formula> after <inline-formula id="ieqn-39"><mml:math id="mml-ieqn-39"><mml:mn>70</mml:mn></mml:math></inline-formula> days, whereas those with <inline-formula id="ieqn-40"><mml:math id="mml-ieqn-40"><mml:mn>60</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> glass fiber under the same conditions has a reduced uptake of <inline-formula id="ieqn-41"><mml:math id="mml-ieqn-41"><mml:mn>0.70</mml:mn><mml:mi mathvariant="normal">&#x0025;</mml:mi></mml:math></inline-formula>. This reduction is attributed to the hydrophobic nature of glass fibers, which, when present in higher amounts, displace the more hydrophilic epoxy matrix and minimize the overall permeable volume. Additionally, higher fiber loading leads to improved barrier effects due to fiber-matrix interlocking, which hinders the penetration of water molecules [<xref ref-type="bibr" rid="ref-22">22</xref>,<xref ref-type="bibr" rid="ref-23">23</xref>].</p>
<p>Similarly, the incorporation of nanoclay significantly enhances moisture resistance. Increasing the nanoclay loading from <inline-formula id="ieqn-42"><mml:math id="mml-ieqn-42"><mml:mn>0</mml:mn></mml:math></inline-formula> to <inline-formula id="ieqn-43"><mml:math id="mml-ieqn-43"><mml:mn>4</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> consistently reduces the water uptake at all time intervals for a fixed glass fiber content. For instance, with <inline-formula id="ieqn-44"><mml:math id="mml-ieqn-44"><mml:mn>40</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> glass fiber, the <inline-formula id="ieqn-45"><mml:math id="mml-ieqn-45"><mml:mn>70</mml:mn></mml:math></inline-formula>-day water uptake drops from <inline-formula id="ieqn-46"><mml:math id="mml-ieqn-46"><mml:mn>0.75</mml:mn><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> (<inline-formula id="ieqn-47"><mml:math id="mml-ieqn-47"><mml:mn>0</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> nanoclay) to <inline-formula id="ieqn-48"><mml:math id="mml-ieqn-48"><mml:mn>0.67</mml:mn><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> (<inline-formula id="ieqn-49"><mml:math id="mml-ieqn-49"><mml:mn>4</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> nanoclay). This improvement is due to the high aspect ratio and platelet-like morphology of nanoclays, which create a tortuous path for water molecules. The dispersion of these particles within the matrix increases the effective diffusion length, thereby reducing the diffusion rate and total water ingress [<xref ref-type="bibr" rid="ref-24">24</xref>,<xref ref-type="bibr" rid="ref-25">25</xref>].</p>
<p>The combined effect of higher glass fiber and nanoclay content is particularly effective. Composites with <inline-formula id="ieqn-50"><mml:math id="mml-ieqn-50"><mml:mn>60</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> glass fiber and <inline-formula id="ieqn-51"><mml:math id="mml-ieqn-51"><mml:mn>4</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> nanoclay exhibit the lowest water uptake percentage across the entire study, with only <inline-formula id="ieqn-52"><mml:math id="mml-ieqn-52"><mml:mn>0.62</mml:mn><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> absorption at day <inline-formula id="ieqn-53"><mml:math id="mml-ieqn-53"><mml:mn>70</mml:mn></mml:math></inline-formula>. This synergy arises from the simultaneous effects of reduced matrix volume (due to higher fiber content) and enhanced diffusion resistance (due to nanoclay inclusion). These observations demonstrate that integrating both reinforcement strategies improves the hydrothermal stability of fiber-reinforced epoxy composites.</p>
<p><italic>Role of Hand Lay-Up and Compression Molding in Controlling Water Uptake (%)</italic></p>
<p>The fabrication process employed in this study involves hand lay-up followed by compression molding at <inline-formula id="ieqn-54"><mml:math id="mml-ieqn-54"><mml:mn>100</mml:mn><mml:mrow><mml:mtext>&#xA0;bar</mml:mtext></mml:mrow></mml:math></inline-formula> pressure and <inline-formula id="ieqn-55"><mml:math id="mml-ieqn-55"><mml:msup><mml:mn>50</mml:mn><mml:mrow><mml:mo>&#x2218;</mml:mo></mml:mrow></mml:msup><mml:mrow><mml:mtext>C</mml:mtext></mml:mrow></mml:math></inline-formula> for <inline-formula id="ieqn-56"><mml:math id="mml-ieqn-56"><mml:mn>24</mml:mn><mml:mrow><mml:mtext>h</mml:mtext></mml:mrow></mml:math></inline-formula>. These processing parameters play a crucial role in determining the composite&#x2019;s void content and interfacial bonding, affecting its water absorption behavior.</p>
<p>Though simple and cost-effective, the hand lay-up technique is susceptible to entrapped air and resin-rich zones if not properly managed. To mitigate this, a roller is used to compress the laminate uniformly and expel trapped air, reducing void formation. The presence of voids can significantly enhance water uptake by providing direct capillary pathways for moisture ingress.</p>
<p>Compression molding under <inline-formula id="ieqn-57"><mml:math id="mml-ieqn-57"><mml:mn>100</mml:mn><mml:mrow><mml:mtext>&#xA0;bar</mml:mtext></mml:mrow></mml:math></inline-formula> pressure enhances consolidation, improving fiber&#x2013;matrix wetting and minimizing porosity. The moderate curing temperature (<inline-formula id="ieqn-58"><mml:math id="mml-ieqn-58"><mml:msup><mml:mn>50</mml:mn><mml:mrow><mml:mo>&#x2218;</mml:mo></mml:mrow></mml:msup><mml:mrow><mml:mtext>C</mml:mtext></mml:mrow></mml:math></inline-formula>) and extended curing time (<inline-formula id="ieqn-59"><mml:math id="mml-ieqn-59"><mml:mn>24</mml:mn><mml:mspace width="thinmathspace" /><mml:mspace width="thinmathspace" /><mml:mrow><mml:mtext>h</mml:mtext></mml:mrow></mml:math></inline-formula>) ensure thorough cross-linking of the epoxy matrix, promoting better interfacial bonding and reducing the number of unreacted groups that may otherwise attract moisture.</p>
<p>Stronger fiber&#x2013;matrix adhesion results in fewer interfacial gaps, which are potential moisture ingress sites. Conversely, insufficient pressure or incomplete curing could lead to poor wetting and weak bonding, promoting microcracks and water diffusion. Therefore, the selected processing parameters are critical for mechanical integrity and improving moisture resistance by lowering void content and strengthening the fiber&#x2013;matrix interface.</p>
</sec>
<sec id="s3_2">
<label>3.2</label>
<title>Artificial Neural Network</title>
<p>The experimental dataset used for training, validation, and testing of the ANN model is derived from the water uptake measurements presented in <xref ref-type="table" rid="table-4">Table 4</xref>, which are obtained from immersion tests on composites with varying soaking time, glass fiber, and nanoclay contents conducted as per ASTM D570-98.</p>

<p>The chosen ANN architecture reflects a balance between model complexity and prediction robustness, avoiding overfitting while capturing nonlinear dependencies between the input variables and moisture absorption behavior. The method exhibits fast convergence within 18 epochs, with the best validation performance achieved early, suggesting effective learning.</p>
<p>The training performance curve in <xref ref-type="fig" rid="fig-3">Fig. 3</xref> reveals a steep decline in Mean Squared Error (MSE) within the first <inline-formula id="ieqn-60"><mml:math id="mml-ieqn-60"><mml:mn>10</mml:mn></mml:math></inline-formula> epochs, after which it asymptotically approaches a minimal error plateau. The optimal validation performance is reached at epoch <inline-formula id="ieqn-61"><mml:math id="mml-ieqn-61"><mml:mn>10</mml:mn></mml:math></inline-formula>, beyond which the validation error starts to increase, indicating the onset of overfitting prevention through early stopping mechanisms. The minimum MSE achieved is approximately <inline-formula id="ieqn-62"><mml:math id="mml-ieqn-62"><mml:mn>1.38</mml:mn><mml:mo>&#x00D7;</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mrow><mml:mo>&#x2212;</mml:mo><mml:mn>4</mml:mn></mml:mrow></mml:msup><mml:mo>,</mml:mo></mml:math></inline-formula>with the best model captured before validation failure increments. The alignment between the training, validation, and testing curves suggests that the network generalizes well without overfitting.</p>
<fig id="fig-3">
<label>Figure 3</label>
<caption>
<title>Training performance of ANN</title>
</caption>
<graphic mimetype="image" mime-subtype="tif" xlink:href="CMC_69842-fig-3.tif"/>
</fig>
<p>The training state plot in <xref ref-type="fig" rid="fig-4">Fig. 4</xref> provides insight into the internal optimization dynamics of the ANN model. The gradient decreases smoothly to <inline-formula id="ieqn-63"><mml:math id="mml-ieqn-63"><mml:mn>7.18</mml:mn><mml:mo>&#x00D7;</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mrow><mml:mo>&#x2212;</mml:mo><mml:mn>5</mml:mn></mml:mrow></mml:msup><mml:mo>,</mml:mo></mml:math></inline-formula> reflecting steady learning progress toward convergence. The <inline-formula id="ieqn-64"><mml:math id="mml-ieqn-64"><mml:mrow><mml:mtext>mu</mml:mtext></mml:mrow></mml:math></inline-formula>, damping parameter, decreases rapidly in the early epochs, stabilizing at <inline-formula id="ieqn-65"><mml:math id="mml-ieqn-65"><mml:msup><mml:mn>10</mml:mn><mml:mrow><mml:mo>&#x2212;</mml:mo><mml:mn>5</mml:mn></mml:mrow></mml:msup></mml:math></inline-formula>, indicative of the model transitioning from global to fine-tuning adjustments. Validation failures remain zero until epoch <inline-formula id="ieqn-66"><mml:math id="mml-ieqn-66"><mml:mn>16</mml:mn></mml:math></inline-formula> after which minor increments are observed, signaling that the model retained a strong generalization ability over a significant portion of the training cycle.</p>
<fig id="fig-4">
<label>Figure 4</label>
<caption>
<title>Training state plot&#x2014;evolution of the gradient, Mu, and validation failure</title>
</caption>
<graphic mimetype="image" mime-subtype="tif" xlink:href="CMC_69842-fig-4.tif"/>
</fig>
<p>Each experimental data point represents the mean of five replicate tests. Standard deviation across replicates is consistently below <inline-formula id="ieqn-67"><mml:math id="mml-ieqn-67"><mml:mo>&#x00B1;</mml:mo><mml:mn>0.02</mml:mn><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula>, indicating high repeatability. For clarity, error bars are omitted from figures, but this statistical consistency supports the model&#x2019;s validity.</p>
<p>The regression plot in <xref ref-type="fig" rid="fig-5">Fig. 5</xref> demonstrates an exceptionally high correlation between the network&#x2019;s predictions and the experimental targets. The coefficient of determination exceeds <inline-formula id="ieqn-68"><mml:math id="mml-ieqn-68"><mml:mn>0.99</mml:mn></mml:math></inline-formula>, validating that the ANN can effectively capture and reproduce the physical relationship between moisture absorption and the composite&#x2019;s formulation and exposure time.</p>
<fig id="fig-5">
<label>Figure 5</label>
<caption>
<title>Regression plot for comparing ANN-predicted water uptake values to experimental targets</title>
</caption>
<graphic mimetype="image" mime-subtype="tif" xlink:href="CMC_69842-fig-5.tif"/>
</fig>
<p>The multi-state regression plot in <xref ref-type="fig" rid="fig-6">Fig. 6</xref> extensively evaluates the ANN&#x2019;s predictive capability across all data splits-training, validation, and testing. All the regression lines are closely aligned with the ideal <inline-formula id="ieqn-69"><mml:math id="mml-ieqn-69"><mml:mi>Y</mml:mi><mml:mo>=</mml:mo><mml:mi>T</mml:mi></mml:math></inline-formula> line, indicating minimal bias and high precision. The overall <inline-formula id="ieqn-70"><mml:math id="mml-ieqn-70"><mml:mi>R</mml:mi><mml:mo>&#x2212;</mml:mo></mml:math></inline-formula>value of 0.998 substantiates that the model maintains consistency and reliability across the entire data spectrum.</p>
<fig id="fig-6">
<label>Figure 6</label>
<caption>
<title>Regression plots for ANN model performance across (<bold>a</bold>) training, (<bold>b</bold>) validation, (<bold>c</bold>) testing, and (<bold>d</bold>) overall data sets</title>
</caption>
<graphic mimetype="image" mime-subtype="tif" xlink:href="CMC_69842-fig-6.tif"/>
</fig>
</sec>
<sec id="s3_3">
<label>3.3</label>
<title>Comparison Data</title>
<p><xref ref-type="fig" rid="fig-7">Fig. 7</xref> directly compares the experimental water uptake (%) values and those predicted by the ANN model across all test conditions. The close alignment between both sets of data points validates the robustness and predictive capability of the trained ANN. This figure underscores the model&#x2019;s ability to generalize across various composite configurations. The minimal deviation between the actual and predicted values reflects a high degree of correlation, which is further supported by regression metrics (with <inline-formula id="ieqn-71"><mml:math id="mml-ieqn-71"><mml:mi>R</mml:mi><mml:mo>&#x2248;</mml:mo><mml:mn>0.998</mml:mn></mml:math></inline-formula>) discussed earlier in <xref ref-type="fig" rid="fig-5">Figs. 5</xref> and <xref ref-type="fig" rid="fig-6">6</xref>. Such an agreement confirms the ANN&#x2019;s suitability for modelling nonlinear, multivariate relationships in composite materials and demonstrates its potential as a surrogate for expensive and time-consuming experimental campaigns.</p>
<fig id="fig-7">
<label>Figure 7</label>
<caption>
<title>Comparison of experimental findings and ANN output</title>
</caption>
<graphic mimetype="image" mime-subtype="tif" xlink:href="CMC_69842-fig-7.tif"/>
</fig>
</sec>
<sec id="s3_4">
<label>3.4</label>
<title>Confirmation Tests</title>
<p><xref ref-type="table" rid="table-5">Table 5</xref> presents the results of independent confirmation tests conducted at selected intermediate immersion durations <inline-formula id="ieqn-72"><mml:math id="mml-ieqn-72"><mml:mo stretchy="false">(</mml:mo><mml:mn>10</mml:mn><mml:mo>,</mml:mo><mml:mn>25</mml:mn><mml:mrow><mml:mtext>&#xA0;and&#xA0;</mml:mtext></mml:mrow><mml:mn>45</mml:mn><mml:mrow><mml:mtext>&#xA0;days</mml:mtext></mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula> that are not part of the ANN training dataset. The experimental water uptake values are directly compared with ANN-predicted outputs for composites with varying glass fiber <inline-formula id="ieqn-73"><mml:math id="mml-ieqn-73"><mml:mo stretchy="false">(</mml:mo><mml:mn>40</mml:mn><mml:mspace width="negativethinmathspace" /><mml:mo>&#x2212;</mml:mo><mml:mspace width="negativethinmathspace" /><mml:mn>60</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula> and nanoclay content <inline-formula id="ieqn-74"><mml:math id="mml-ieqn-74"><mml:mrow><mml:mo>(</mml:mo><mml:mn>0</mml:mn><mml:mspace width="negativethinmathspace" /><mml:mo>&#x2212;</mml:mo><mml:mspace width="negativethinmathspace" /><mml:mn>4</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow><mml:mo>)</mml:mo></mml:mrow><mml:mo>.</mml:mo></mml:math></inline-formula> The observed differences between experimental and predicted values are minimal, generally within <inline-formula id="ieqn-75"><mml:math id="mml-ieqn-75"><mml:mo>&#x00B1;</mml:mo><mml:mn>0.015</mml:mn><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula>, demonstrating excellent predictive performance.</p>
<table-wrap id="table-5">
<label>Table 5</label>
<caption>
<title>Confirmation tests for different days</title>
</caption>
<table>
<colgroup>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
</colgroup>
<thead>
<tr>
<th align="center">Days</th>
<th align="center">Glass fiber <bold>(wt.%)</bold></th>
<th align="center">Nanoclay <bold>(wt.%)</bold></th>
<th align="center">Water uptake <bold>(%)</bold></th>
<th align="center">ANN predicted</th>
<th align="center">Absolute error <bold>(%)</bold></th>
</tr>
</thead>
<tbody>
<tr>
<td>25</td>
<td>40</td>
<td>0</td>
<td>0.59</td>
<td>0.594</td>
<td>0.004</td>
</tr>
<tr>
<td>25</td>
<td>40</td>
<td>2</td>
<td>0.53</td>
<td>0.552</td>
<td>0.022</td>
</tr>
<tr>
<td>25</td>
<td>40</td>
<td>4</td>
<td>0.48</td>
<td>0.504</td>
<td>0.024</td>
</tr>
<tr>
<td>45</td>
<td>50</td>
<td>0</td>
<td>0.69</td>
<td>0.681</td>
<td>0.009</td>
</tr>
<tr>
<td>45</td>
<td>50</td>
<td>2</td>
<td>0.65</td>
<td>0.636</td>
<td>0.014</td>
</tr>
<tr>
<td>45</td>
<td>50</td>
<td>4</td>
<td>0.61</td>
<td>0.597</td>
<td>0.013</td>
</tr>
<tr>
<td>10</td>
<td>60</td>
<td>0</td>
<td>0.32</td>
<td>0.324</td>
<td>0.004</td>
</tr>
<tr>
<td>10</td>
<td>60</td>
<td>2</td>
<td>0.28</td>
<td>0.285</td>
<td>0.005</td>
</tr>
<tr>
<td>10</td>
<td>60</td>
<td>4</td>
<td>0.25</td>
<td>0.24</td>
<td>0.010</td>
</tr>
</tbody>
</table>
</table-wrap>
<p>For instance, the water uptake for a composite with <inline-formula id="ieqn-76"><mml:math id="mml-ieqn-76"><mml:mn>40</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> glass fiber and <inline-formula id="ieqn-77"><mml:math id="mml-ieqn-77"><mml:mn>0</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> nanoclay after <inline-formula id="ieqn-78"><mml:math id="mml-ieqn-78"><mml:mn>25</mml:mn><mml:mrow><mml:mtext>&#xA0;days</mml:mtext></mml:mrow></mml:math></inline-formula> is measured as <inline-formula id="ieqn-79"><mml:math id="mml-ieqn-79"><mml:mn>0.59</mml:mn><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow><mml:mo>,</mml:mo></mml:math></inline-formula> while the ANN predicted <inline-formula id="ieqn-80"><mml:math id="mml-ieqn-80"><mml:mn>0.594</mml:mn><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula>. Similarly, for a <inline-formula id="ieqn-81"><mml:math id="mml-ieqn-81"><mml:mn>60</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> glass fiber and <inline-formula id="ieqn-82"><mml:math id="mml-ieqn-82"><mml:mn>4</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> nanoclay sample at <inline-formula id="ieqn-83"><mml:math id="mml-ieqn-83"><mml:mn>10</mml:mn><mml:mrow><mml:mtext>&#xA0;days</mml:mtext></mml:mrow></mml:math></inline-formula>, the measured uptake is <inline-formula id="ieqn-84"><mml:math id="mml-ieqn-84"><mml:mn>0.25</mml:mn><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula>, closely matching the predicted value of <inline-formula id="ieqn-85"><mml:math id="mml-ieqn-85"><mml:mn>0.24</mml:mn><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula>. These results affirm the ANN robustness and ability to interpolate accurately within the tested parameter space. Such validation further strengthens the model&#x2019;s applicability in reducing experimental workloads and expediting moisture-related performance assessment in nanoclay-modified composite systems.</p>
</sec>
</sec>
<sec id="s4">
<label>4</label>
<title>Conclusion</title>
<p>This study focuses on developing an ANN model to predict water uptake behavior in nanoclay-modified glass fiber/epoxy composites subjected to prolonged immersion. Composite laminates are fabricated with varying glass fiber <inline-formula id="ieqn-86"><mml:math id="mml-ieqn-86"><mml:mo stretchy="false">(</mml:mo><mml:mn>40</mml:mn><mml:mspace width="negativethinmathspace" /><mml:mo>&#x2212;</mml:mo><mml:mspace width="negativethinmathspace" /><mml:mn>60</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula> and nanoclay <inline-formula id="ieqn-87"><mml:math id="mml-ieqn-87"><mml:mo stretchy="false">(</mml:mo><mml:mn>0</mml:mn><mml:mspace width="negativethinmathspace" /><mml:mo>&#x2212;</mml:mo><mml:mspace width="negativethinmathspace" /><mml:mn>4</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula> contents, and their water absorption behavior is experimentally evaluated over 7<inline-formula id="ieqn-88"><mml:math id="mml-ieqn-88"><mml:mn>0</mml:mn><mml:mrow><mml:mtext>&#xA0;days</mml:mtext></mml:mrow></mml:math></inline-formula>.</p>
<p>The developed ANN model accurately predicts water uptake in nanoclay-modified glass fiber/epoxy composites with an <inline-formula id="ieqn-89"><mml:math id="mml-ieqn-89"><mml:msup><mml:mi>R</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:math></inline-formula> of <inline-formula id="ieqn-90"><mml:math id="mml-ieqn-90"><mml:mn>0.998</mml:mn></mml:math></inline-formula> and minimal prediction error <inline-formula id="ieqn-91"><mml:math id="mml-ieqn-91"><mml:mo stretchy="false">(</mml:mo><mml:mo>&#x00B1;</mml:mo><mml:mn>0.015</mml:mn><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula>. Incorporating <inline-formula id="ieqn-92"><mml:math id="mml-ieqn-92"><mml:mn>4</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> nanoclay led to a <inline-formula id="ieqn-93"><mml:math id="mml-ieqn-93"><mml:mo>&#x223C;</mml:mo><mml:mspace width="negativethinmathspace" /><mml:mspace width="negativethinmathspace" /><mml:mn>11</mml:mn><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> reduction in water uptake at <inline-formula id="ieqn-94"><mml:math id="mml-ieqn-94"><mml:mn>10</mml:mn><mml:mrow><mml:mtext>&#xA0;days</mml:mtext></mml:mrow></mml:math></inline-formula> compared to composites without nanoclay. Similarly, increasing glass fiber from <inline-formula id="ieqn-95"><mml:math id="mml-ieqn-95"><mml:mn>40</mml:mn></mml:math></inline-formula> to <inline-formula id="ieqn-96"><mml:math id="mml-ieqn-96"><mml:mn>60</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula> reduces water absorption by <inline-formula id="ieqn-97"><mml:math id="mml-ieqn-97"><mml:mo>&#x223C;</mml:mo><mml:mspace width="negativethinmathspace" /><mml:mspace width="negativethinmathspace" /><mml:mn>7</mml:mn><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula>. The ANN model reliably captures these nonlinear effects, offering a cost-effective alternative to long-duration testing and enabling faster material optimization in moisture-sensitive composite applications.</p>
<p>These findings offer practical value for industrial composite design by enabling significant reductions in prototype testing and development time. The validated ANN model provides a fast, cost-effective tool for predicting moisture uptake across various formulations, allowing early-stage screening and optimization without extensive experimental trials. This approach supports accelerated design cycles and efficient material selection for moisture-critical applications.</p>
<p>The current ANN model is trained solely in water immersion data at room temperature <inline-formula id="ieqn-98"><mml:math id="mml-ieqn-98"><mml:mo>&#x223C;</mml:mo><mml:mspace width="negativethinmathspace" /><mml:mspace width="negativethinmathspace" /><mml:msup><mml:mn>25</mml:mn><mml:mrow><mml:mo>&#x2218;</mml:mo></mml:mrow></mml:msup><mml:mrow><mml:mtext>C</mml:mtext></mml:mrow></mml:math></inline-formula> using tap water and nanoclay contents of <inline-formula id="ieqn-99"><mml:math id="mml-ieqn-99"><mml:mn>0</mml:mn><mml:mo>,</mml:mo><mml:mn>2</mml:mn><mml:mrow><mml:mtext>&#xA0;and&#xA0;</mml:mtext></mml:mrow><mml:mn>4</mml:mn><mml:mrow><mml:mtext>&#xA0;wt</mml:mtext></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:mtext>%&#xA0;</mml:mtext></mml:mrow></mml:math></inline-formula>. Therefore, predictions are limited to these conditions and may not be accurate for different temperatures, immersion media, or nanoparticle types and concentrations. To improve its applicability, future work should include additional inputs like immersion temperature, pH, and filler type, enabling the model to predict water uptake under varied conditions for real-world durability assessments.</p>
</sec>
</body>
<back>
<ack>
<p>None.</p>
</ack>
<sec>
<title>Funding Statement</title>
<p>The authors received no specific funding for this study.</p>
</sec>
<sec>
<title>Author Contributions</title>
<p>The authors confirm contribution to the paper as follows: Conceptualization, Ashwini Bhat and Manjunath Shettar; methodology, Ashwini Bhat and Manjunath Shettar; software, Ashwini Bhat; validation, Ashwini Bhat, Nagaraj N. Katagi and M. C. Gowrishankar; formal analysis, Ashwini Bhat; investigation, M. C. Gowrishankar and Manjunath Shettar; resources, M. C. Gowrishankar and Manjunath Shettar; data curation, M. C. Gowrishankar and Manjunath Shettar; writing&#x2014;original draft preparation, Ashwini Bhat and Nagaraj N. Katagi; writing&#x2014;review and editing, M. C. Gowrishankar and Manjunath Shettar; visualization, Manjunath Shettar; supervision, Manjunath Shettar; project administration, Manjunath Shettar. All authors reviewed the results and approved the final version of the manuscript.</p>
</sec>
<sec sec-type="data-availability">
<title>Availability of Data and Materials</title>
<p>The authors confirm that the data supporting the findings of this study are available within the article.</p>
</sec>
<sec>
<title>Ethics Approval</title>
<p>Not applicable.</p>
</sec>
<sec sec-type="COI-statement">
<title>Conflicts of Interest</title>
<p>The authors declare no conflicts of interest to report regarding the present study.</p>
</sec>
<ref-list content-type="authoryear">
<title>References</title>
<ref id="ref-1"><label>[1]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Dinit&#x0103;</surname> <given-names>A</given-names></string-name>, <string-name><surname>Ripeanu</surname> <given-names>RG</given-names></string-name>, <string-name><surname>Ilinc&#x0103;</surname> <given-names>CN</given-names></string-name>, <string-name><surname>Cursaru</surname> <given-names>D</given-names></string-name>, <string-name><surname>Matei</surname> <given-names>D</given-names></string-name>, <string-name><surname>Naim</surname> <given-names>RI</given-names></string-name>, <etal>et al</etal></person-group>. <article-title>Advancements in fiber-reinforced polymer composites: a comprehensive analysis</article-title>. <source>Polymers</source>. <year>2023</year>;<volume>16</volume>(<issue>1</issue>):<fpage>2</fpage>. doi:<pub-id pub-id-type="doi">10.3390/polym16010002</pub-id>; <pub-id pub-id-type="pmid">38201669</pub-id></mixed-citation></ref>
<ref id="ref-2"><label>[2]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Hamzat</surname> <given-names>AK</given-names></string-name>, <string-name><surname>Murad</surname> <given-names>MS</given-names></string-name>, <string-name><surname>Adediran</surname> <given-names>IA</given-names></string-name>, <string-name><surname>Asmatulu</surname> <given-names>E</given-names></string-name>, <string-name><surname>Asmatulu</surname> <given-names>R</given-names></string-name></person-group>. <article-title>Fiber-reinforced composites for aerospace, energy, and marine applications: an insight into failure mechanisms under chemical, thermal, oxidative, and mechanical load conditions</article-title>. <source>Adv Compos Hybrid Mater</source>. <year>2025</year>;<volume>8</volume>(<issue>1</issue>):<fpage>152</fpage>. doi:<pub-id pub-id-type="doi">10.1007/s42114-024-01192-y</pub-id>.</mixed-citation></ref>
<ref id="ref-3"><label>[3]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Harle</surname> <given-names>SM</given-names></string-name></person-group>. <article-title>Durability and long-term performance of fiber reinforced polymer (FRP) composites: a review</article-title>. <source>Structures</source>. <year>2024</year>;<volume>60</volume>(<issue>31</issue>):<fpage>105881</fpage>. doi:<pub-id pub-id-type="doi">10.1016/j.istruc.2024.105881</pub-id>.</mixed-citation></ref>
<ref id="ref-4"><label>[4]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Idrisi</surname> <given-names>AH</given-names></string-name>, <string-name><surname>Mourad</surname> <given-names>AHI</given-names></string-name>, <string-name><surname>Abdel-Magid</surname> <given-names>BM</given-names></string-name>, <string-name><surname>Shivamurty</surname> <given-names>B</given-names></string-name></person-group>. <article-title>Investigation on the durability of E-glass/epoxy composite exposed to seawater at elevated temperature</article-title>. <source>Polymers</source>. <year>2021</year>;<volume>13</volume>(<issue>13</issue>):<fpage>2182</fpage>. doi:<pub-id pub-id-type="doi">10.3390/polym13132182</pub-id>; <pub-id pub-id-type="pmid">34209208</pub-id></mixed-citation></ref>
<ref id="ref-5"><label>[5]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Ejeta</surname> <given-names>LO</given-names></string-name></person-group>. <article-title>Nanoclay/organic filler-reinforced polymeric hybrid composites as promising materials for building, automotive, and construction applications&#x2014;a state-of-the-art review</article-title>. <source>Compos Interfaces</source>. <year>2023</year>;<volume>30</volume>(<issue>12</issue>):<fpage>1363</fpage>&#x2013;<lpage>86</lpage>. doi:<pub-id pub-id-type="doi">10.1080/09276440.2023.2220217</pub-id>.</mixed-citation></ref>
<ref id="ref-6"><label>[6]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Shelly</surname> <given-names>D</given-names></string-name>, <string-name><surname>Singhal</surname> <given-names>V</given-names></string-name>, <string-name><surname>Singh</surname> <given-names>S</given-names></string-name>, <string-name><surname>Nanda</surname> <given-names>T</given-names></string-name>, <string-name><surname>Mehta</surname> <given-names>R</given-names></string-name>, <string-name><surname>Lee</surname> <given-names>SY</given-names></string-name>, <etal>et al</etal></person-group>. <article-title>Exploring the impact of nanoclay on epoxy nanocomposites: a comprehensive review</article-title>. <source>J Compos Sci</source>. <year>2024</year>;<volume>8</volume>(<issue>12</issue>):<fpage>506</fpage>. doi:<pub-id pub-id-type="doi">10.3390/jcs8120506</pub-id>.</mixed-citation></ref>
<ref id="ref-7"><label>[7]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Merah</surname> <given-names>N</given-names></string-name>, <string-name><surname>Ashraf</surname> <given-names>F</given-names></string-name>, <string-name><surname>Shaukat</surname> <given-names>MM</given-names></string-name></person-group>. <article-title>Mechanical and moisture barrier properties of epoxy-nanoclay and hybrid epoxy-nanoclay glass fibre composites: a review</article-title>. <source>Polymers</source>. <year>2022</year>;<volume>14</volume>(<issue>8</issue>):<fpage>1620</fpage>. doi:<pub-id pub-id-type="doi">10.3390/polym14081620</pub-id>; <pub-id pub-id-type="pmid">35458370</pub-id></mixed-citation></ref>
<ref id="ref-8"><label>[8]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Uddin</surname> <given-names>MN</given-names></string-name>, <string-name><surname>Hossain</surname> <given-names>MT</given-names></string-name>, <string-name><surname>Mahmud</surname> <given-names>N</given-names></string-name>, <string-name><surname>Alam</surname> <given-names>S</given-names></string-name>, <string-name><surname>Jobaer</surname> <given-names>M</given-names></string-name>, <string-name><surname>Mahedi</surname> <given-names>SI</given-names></string-name>, <etal>et al</etal></person-group>. <article-title>Research and applications of nanoclays: a review</article-title>. <source>SPE Polym</source>. <year>2024</year>;<volume>5</volume>(<issue>4</issue>):<fpage>507</fpage>&#x2013;<lpage>35</lpage>. doi:<pub-id pub-id-type="doi">10.1002/pls2.10146</pub-id>.</mixed-citation></ref>
<ref id="ref-9"><label>[9]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>&#x00D6;r&#x00E7;en</surname> <given-names>G</given-names></string-name>, <string-name><surname>Bayram</surname> <given-names>D</given-names></string-name></person-group>. <article-title>Effect of nanoclay on the mechanical and thermal properties of glass fiber-reinforced epoxy composites</article-title>. <source>J Mater Sci</source>. <year>2024</year>;<volume>59</volume>(<issue>8</issue>):<fpage>3467</fpage>&#x2013;<lpage>87</lpage>. doi:<pub-id pub-id-type="doi">10.1007/s10853-024-09387-w</pub-id>.</mixed-citation></ref>
<ref id="ref-10"><label>[10]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Shettar</surname> <given-names>M</given-names></string-name>, <string-name><surname>Bhat</surname> <given-names>A</given-names></string-name>, <string-name><surname>Katagi</surname> <given-names>NN</given-names></string-name>, <string-name><surname>Gowrishankar</surname> <given-names>MC</given-names></string-name></person-group>. <article-title>Experimental investigation on mechanical properties of glass fiber&#x2013;nanoclay&#x2013;epoxy composites under water-soaking: a comparative study using RSM and ANN</article-title>. <source>J Compos Sci</source>. <year>2025</year>;<volume>9</volume>(<issue>4</issue>):<fpage>195</fpage>. doi:<pub-id pub-id-type="doi">10.3390/jcs9040195</pub-id>.</mixed-citation></ref>
<ref id="ref-11"><label>[11]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Champa-Bujaico</surname> <given-names>E</given-names></string-name>, <string-name><surname>Garc&#x00ED;a-D&#x00ED;az</surname> <given-names>P</given-names></string-name>, <string-name><surname>D&#x00ED;ez-Pascual</surname> <given-names>AM</given-names></string-name></person-group>. <article-title>Machine learning for property prediction and optimization of polymeric nanocomposites: a state-of-the-art</article-title>. <source>Int J Mol Sci</source>. <year>2022</year>;<volume>23</volume>(<issue>18</issue>):<fpage>10712</fpage>. doi:<pub-id pub-id-type="doi">10.3390/ijms231810712</pub-id>; <pub-id pub-id-type="pmid">36142623</pub-id></mixed-citation></ref>
<ref id="ref-12"><label>[12]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Kumar</surname> <given-names>DS</given-names></string-name>, <string-name><surname>Sathish</surname> <given-names>T</given-names></string-name>, <string-name><surname>Rangappa</surname> <given-names>SM</given-names></string-name>, <string-name><surname>Boonyasopon</surname> <given-names>P</given-names></string-name>, <string-name><surname>Siengchin</surname> <given-names>S</given-names></string-name></person-group>. <article-title>Mechanical property analysis of nanocarbon particles/glass fiber reinforced hybrid epoxy composites using RSM</article-title>. <source>Compos Commun</source>. <year>2022</year>;<volume>32</volume>(<issue>23</issue>):<fpage>101147</fpage>. doi:<pub-id pub-id-type="doi">10.1016/j.coco.2022.101147</pub-id>.</mixed-citation></ref>
<ref id="ref-13"><label>[13]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Thanikodi</surname> <given-names>S</given-names></string-name>, <string-name><surname>Rathinasamy</surname> <given-names>S</given-names></string-name>, <string-name><surname>Solairaju</surname> <given-names>JA</given-names></string-name></person-group>. <article-title>Developing a model to predict and optimize the flexural and impact properties of jute/kenaf fiber nano-composite using response surface methodology</article-title>. <source>Int J Adv Manuf Technol</source>. <year>2025</year>;<volume>136</volume>(<issue>1</issue>):<fpage>195</fpage>&#x2013;<lpage>209</lpage>. doi:<pub-id pub-id-type="doi">10.1007/s00170-024-13975-0</pub-id>.</mixed-citation></ref>
<ref id="ref-14"><label>[14]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Arunachalam</surname> <given-names>SJ</given-names></string-name>, <string-name><surname>Saravanan</surname> <given-names>R</given-names></string-name>, <string-name><surname>Sathish</surname> <given-names>T</given-names></string-name>, <string-name><surname>Giri</surname> <given-names>J</given-names></string-name>, <string-name><surname>Kanan</surname> <given-names>M</given-names></string-name></person-group>. <article-title>Mechanical assessment for enhancing hybrid composite performance through silane treatment using RSM and ANN</article-title>. <source>Results Eng</source>. <year>2024</year>;<volume>24</volume>(<issue>1</issue>):<fpage>103309</fpage>. doi:<pub-id pub-id-type="doi">10.1016/j.rineng.2024.103309</pub-id>.</mixed-citation></ref>
<ref id="ref-15"><label>[15]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Arunachalam</surname> <given-names>SJ</given-names></string-name>, <string-name><surname>Saravanan</surname> <given-names>R</given-names></string-name>, <string-name><surname>Sathish</surname> <given-names>T</given-names></string-name>, <string-name><surname>Giri</surname> <given-names>J</given-names></string-name>, <string-name><surname>Barmavatu</surname> <given-names>P</given-names></string-name></person-group>. <article-title>Optimization of nano-filler and silane treatment on mechanical performance of nanographene hybrid composites using RSM and ANN technique</article-title>. <source>J Adhes Sci Technol</source>. <year>2025</year>;<volume>39</volume>(<issue>2</issue>):<fpage>257</fpage>&#x2013;<lpage>80</lpage>. doi:<pub-id pub-id-type="doi">10.1080/01694243.2024.2403680</pub-id>.</mixed-citation></ref>
<ref id="ref-16"><label>[16]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Y&#x0131;ld&#x0131;r&#x0131;m</surname> <given-names>H</given-names></string-name></person-group>. <article-title>Prediction of weight change of glass fiber reinforced polymer matrix composites with SiC nanoparticles after artificial aging by artificial neural network-based model</article-title>. <source>J Mater Sci</source>. <year>2025</year>;<volume>60</volume>(<issue>11</issue>):<fpage>5064</fpage>&#x2013;<lpage>79</lpage>. doi:<pub-id pub-id-type="doi">10.1007/s10853-025-10747-3</pub-id>.</mixed-citation></ref>
<ref id="ref-17"><label>[17]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Capiel</surname> <given-names>G</given-names></string-name>, <string-name><surname>Florencia</surname> <given-names>A</given-names></string-name>, <string-name><surname>Alvarez</surname> <given-names>VA</given-names></string-name>, <string-name><surname>Montemartini</surname> <given-names>PE</given-names></string-name>, <string-name><surname>Mor&#x00E1;n</surname> <given-names>J</given-names></string-name></person-group>. <article-title>An Artificial Neural Network (ANN) model for predicting water absorption of Nanoclay-Epoxy composites</article-title>. <source>J Mater Sci Chem Eng</source>. <year>2019</year>;<volume>7</volume>(<issue>8</issue>):<fpage>87</fpage>&#x2013;<lpage>97</lpage>. doi:<pub-id pub-id-type="doi">10.4236/msce.2019.78010</pub-id>.</mixed-citation></ref>
<ref id="ref-18"><label>[18]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Saaidia</surname> <given-names>A</given-names></string-name>, <string-name><surname>Belaadi</surname> <given-names>A</given-names></string-name>, <string-name><surname>Boumaaza</surname> <given-names>M</given-names></string-name>, <string-name><surname>Alshahrani</surname> <given-names>H</given-names></string-name>, <string-name><surname>Bourchak</surname> <given-names>M</given-names></string-name></person-group>. <article-title>Effect of water absorption on the behavior of jute and sisal fiber biocomposites at different lengths: ANN and RSM modeling</article-title>. <source>J Nat Fibers</source>. <year>2023</year>;<volume>20</volume>(<issue>1</issue>):<fpage>2140326</fpage>. doi:<pub-id pub-id-type="doi">10.1080/15440478.2022.2140326</pub-id>.</mixed-citation></ref>
<ref id="ref-19"><label>[19]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Makhlouf</surname> <given-names>A</given-names></string-name>, <string-name><surname>Belaadi</surname> <given-names>A</given-names></string-name>, <string-name><surname>Boumaaza</surname> <given-names>M</given-names></string-name>, <string-name><surname>Mansouri</surname> <given-names>L</given-names></string-name>, <string-name><surname>Bourchak</surname> <given-names>M</given-names></string-name>, <string-name><surname>Jawaid</surname> <given-names>M</given-names></string-name></person-group>. <article-title>Water Absorption behavior of jute fibers reinforced HDPE biocomposites: prediction using RSM and ANN modeling</article-title>. <source>J Nat Fibers</source>. <year>2022</year>;<volume>19</volume>(<issue>16</issue>):<fpage>14014</fpage>&#x2013;<lpage>31</lpage>. doi:<pub-id pub-id-type="doi">10.1080/15440478.2022.2114976</pub-id>.</mixed-citation></ref>
<ref id="ref-20"><label>[20]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Shettar</surname> <given-names>M</given-names></string-name>, <string-name><surname>Bhat</surname> <given-names>A</given-names></string-name>, <string-name><surname>Katagi</surname> <given-names>NN</given-names></string-name></person-group>. <article-title>Estimation of mass loss under wear test of nanoclay-epoxy nanocomposite using response surface methodology and artificial neural networks</article-title>. <source>Sci Rep</source>. <year>2025</year>;<volume>15</volume>(<issue>1</issue>):<fpage>19978</fpage>. doi:<pub-id pub-id-type="doi">10.1038/s41598-025-05263-y</pub-id>; <pub-id pub-id-type="pmid">40481159</pub-id></mixed-citation></ref>
<ref id="ref-21"><label>[21]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Manaia</surname> <given-names>JP</given-names></string-name>, <string-name><surname>Manaia</surname> <given-names>A</given-names></string-name></person-group>. <article-title>Interface modification, water absorption behaviour and mechanical properties of injection moulded short hemp fiber-reinforced thermoplastic composites</article-title>. <source>Polymers</source>. <year>2021</year>;<volume>13</volume>(<issue>10</issue>):<fpage>1638</fpage>. doi:<pub-id pub-id-type="doi">10.3390/polym13101638</pub-id>; <pub-id pub-id-type="pmid">34070199</pub-id></mixed-citation></ref>
<ref id="ref-22"><label>[22]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Borges</surname> <given-names>CSP</given-names></string-name>, <string-name><surname>Akhavan-Safar</surname> <given-names>A</given-names></string-name>, <string-name><surname>Marques</surname> <given-names>EAS</given-names></string-name>, <string-name><surname>Carbas</surname> <given-names>RJC</given-names></string-name>, <string-name><surname>Ueffing</surname> <given-names>C</given-names></string-name>, <string-name><surname>Wei&#x00DF;graeber</surname> <given-names>P</given-names></string-name>, <etal>et al</etal></person-group>. <article-title>Effect of water ingress on the mechanical and chemical properties of polybutylene terephthalate reinforced with glass fibers</article-title>. <source>Materials</source>. <year>2021</year>;<volume>14</volume>(<issue>5</issue>):<fpage>1261</fpage>. doi:<pub-id pub-id-type="doi">10.3390/ma14051261</pub-id>; <pub-id pub-id-type="pmid">33799962</pub-id></mixed-citation></ref>
<ref id="ref-23"><label>[23]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Cheng</surname> <given-names>W</given-names></string-name>, <string-name><surname>Cao</surname> <given-names>Y</given-names></string-name></person-group>. <article-title>Strength degradation of GFRP cross-ply laminates in hydrothermal conditions</article-title>. <source>APL Mater</source>. <year>2024</year>;<volume>12</volume>(<issue>3</issue>):<fpage>031113</fpage>. doi:<pub-id pub-id-type="doi">10.1063/5.0201999</pub-id>.</mixed-citation></ref>
<ref id="ref-24"><label>[24]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Gowrishankar</surname> <given-names>MC</given-names></string-name>, <string-name><surname>Shettar</surname> <given-names>M</given-names></string-name>, <string-name><surname>Somdee</surname> <given-names>P</given-names></string-name>, <string-name><surname>Rangaswamy</surname> <given-names>N</given-names></string-name>, <string-name><surname>Chate</surname> <given-names>GR</given-names></string-name></person-group>. <article-title>A review on mechanical, water-soaking, thermal, and wear properties of nanoclay-polyester nanocomposites</article-title>. <source>Discov Mater</source>. <year>2025</year>;<volume>5</volume>(<issue>1</issue>):<fpage>105</fpage>. doi:<pub-id pub-id-type="doi">10.1007/s43939-025-00304-9</pub-id>.</mixed-citation></ref>
<ref id="ref-25"><label>[25]</label><mixed-citation publication-type="journal"><person-group person-group-type="author"><string-name><surname>Rafiq</surname> <given-names>A</given-names></string-name>, <string-name><surname>Merah</surname> <given-names>N</given-names></string-name></person-group>. <article-title>Nanoclay enhancement of flexural properties and water uptake resistance of glass fiber-reinforced epoxy composites at different temperatures</article-title>. <source>J Compos Mater</source>. <year>2019</year>;<volume>53</volume>(<issue>2</issue>):<fpage>143</fpage>&#x2013;<lpage>54</lpage>. doi:<pub-id pub-id-type="doi">10.1177/0021998318781220</pub-id>.</mixed-citation></ref>
</ref-list>
</back></article>