Stacking Sequence‐Driven Hydrothermal Durability in Woven Carbon/Glass/Kevlar Epoxy Hybrid Laminates

ABSTRACT

Hybrid fiber‐reinforced polymer (FRP) composites are becoming prominent structural materials due to their high specific strength, design flexibility, and suitability for aerospace, marine, and defense applications. This study investigates the influence of stacking sequence on water absorption, flexural, and impact properties of Carbon/Glass/Kevlar epoxy hybrid laminates. Eight different stacking sequences: plain (C7, G7, K7) and hybrid (G2K3G2, KG2CG2K, CKGCGKC, CGKCKGC, CK2CK2C) epoxy laminates were manufactured for comparative evaluation of dry and water‐aged specimens. For plain composites, carbon (C7) composites revealed the most favorable properties with respect to flexural strength (613 MPa) and flexural modulus (37.85 GPa). Of the hybrid composites, those with the greatest carbon content (CGKCKGC) also exhibited the highest flexural strength (411 MPa). Water immersion led to 4% gains in mass for CK2CK2C owing to the hydrophilic nature of Kevlar's amide groups, weakening fiber‐matrix interface strength. G2K3G2 achieved the most resistant impact behavior (126 kJ/m ² ), confirming that hybridized glass/Kevlar composites improve energy absorption, but hydrothermal exposure diminishes impact strength for Kevlar‐rich composites. Diffusion coefficients ranged from 1.310 × 10 ⁻¹¹  m ² /s for CGKCKGC to 2.421 × 10 ⁻¹¹  m ² /s for G7, with K7 exhibiting the highest moisture uptake (~5%). Post‐aging flexural strength retention was highest for C7 and CGKCKGC, while K7 suffered a 45% reduction in impact strength after hydrothermal exposure, confirming that stacking sequence governs both as‐fabricated performance and hydrothermal durability.