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<p>This study investigates the influence of nitrile butadiene rubber (NBR) on the tensile and fracture behavior of epoxy composites reinforced with woven S-glass fibers. Laminates were fabricated with varying NBR concentrations (0, 5, 10, and 15 wt.%) and assessed through standardised tensile and Mode I intralaminar fracture assessments in accordance with ASTM guidelines. A progressive improvement in peak tensile strength was observed with the addition of NBR, reaching 141.6 ± 2.1&#xa0;MPa for the 15 wt.% NBR formulation, while the elastic modulus decreased to 16.8 ± 0.5 GPa. While NBR addition led to a steady increase in bulk tensile toughness due to enhanced matrix ductility, the Mode 1 fracture toughness (K<sub>IC</sub>) also improved rising from 1.02 ± 0.06&#xa0;MPa <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\sqrt{m}\)</EquationSource> <EquationSource Format="MATHML"><math> <msqrt> <mi>m</mi> </msqrt> </math></EquationSource> </InlineEquation> to 1.38 ± 0.08&#xa0;MPa <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\sqrt{m}\)</EquationSource> <EquationSource Format="MATHML"><math> <msqrt> <mi>m</mi> </msqrt> </math></EquationSource> </InlineEquation> at a crack length of 5.8&#xa0;mm. The observed decline in K<sub>IC</sub> with increasing crack length (a/W) is attributed to R- curve behavior, where the effectiveness of rubber-bridging and energy dissipation mechanisms is most potent during initial stages of crack growth. The improvement is attributed to energy dissipation mechanisms such as crack blunting, matrix yielding, and enhanced fiber-matrix adhesion, as confirmed by SEM micrographs. Although there was a slight increase in the void content, all the values were within acceptable engineering limits. The results indicate that NBR is effective in enhancing the strength and damage tolerance of S-glass/epoxy composites to enable their application in the construction of structures that demand greater strength and fracture resistance.</p>

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Mode-I Fracture Toughness and Tensile Behaviour of S-Glass/Epoxy Composites Modified with Nitrile Butadiene Rubber

  • 期刊论文

  • 发表日期：

    2026年4月10日

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  • C Hemanth Kumar,
  • SLN Jayasimha

摘要

This study investigates the influence of nitrile butadiene rubber (NBR) on the tensile and fracture behavior of epoxy composites reinforced with woven S-glass fibers. Laminates were fabricated with varying NBR concentrations (0, 5, 10, and 15 wt.%) and assessed through standardised tensile and Mode I intralaminar fracture assessments in accordance with ASTM guidelines. A progressive improvement in peak tensile strength was observed with the addition of NBR, reaching 141.6 ± 2.1 MPa for the 15 wt.% NBR formulation, while the elastic modulus decreased to 16.8 ± 0.5 GPa. While NBR addition led to a steady increase in bulk tensile toughness due to enhanced matrix ductility, the Mode 1 fracture toughness (KIC) also improved rising from 1.02 ± 0.06 MPa \(\sqrt{m}\) m to 1.38 ± 0.08 MPa \(\sqrt{m}\) m at a crack length of 5.8 mm. The observed decline in KIC with increasing crack length (a/W) is attributed to R- curve behavior, where the effectiveness of rubber-bridging and energy dissipation mechanisms is most potent during initial stages of crack growth. The improvement is attributed to energy dissipation mechanisms such as crack blunting, matrix yielding, and enhanced fiber-matrix adhesion, as confirmed by SEM micrographs. Although there was a slight increase in the void content, all the values were within acceptable engineering limits. The results indicate that NBR is effective in enhancing the strength and damage tolerance of S-glass/epoxy composites to enable their application in the construction of structures that demand greater strength and fracture resistance.