International Journal of Advanced Engineering Application

Fatigue Behaviour, Failure Mechanisms and Environmental Trade-offs of Carbon-, Glass- and Hybrid-Fibre Reinforced Polymer Composites Under Variable-Amplitude Cyclic Loading

Author(s):Arjun Krishnamurthy

Affiliation: Department of Aerospace and Mechanical Engineering, Amity University, India

Page No: 6-11

Volume issue & Publishing Year: Volume 3, Issue 7, 2026/07/01

Journal: International Journal of Advanced Engineering Application (IJAEA)

ISSN NO: 3048-6807

DOI:

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Abstract:
Fibre reinforced polymer (FRP) composites are displacing metallic structures across aerospace, wind energy, and automotive sectors; however, their fatigue behaviour under variable-amplitude (VA) loading — the spectrum experienced by service structures — remains less systematically characterised than constant-amplitude performance. This study conducts a comprehensive multi-material fatigue investigation of unidirectional and woven-weave (WV) carbon fibre reinforced polymer (CFRP), E-glass FRP (GFRP), and an interleaved carbon–glass hybrid (Hybrid), all using a standard aerospace-grade amine-cured epoxy matrix, alongside a structural steel control. S–N curves at stress ratios R = 0.1 and R = 0.5 were generated for each system; progressive stiffness degradation, inter-laminar shear strength (ILSS), void fraction by optical microscopy, and failure mode fractography under SEM are reported. Load–displacement response of 300 × 40 × 4 mm specimens under quasi-static three-point bending and thermogravimetric analysis (TGA) at 10 °C/min complement the fatigue dataset. Environmental performance is quantified through embodied CO₂ intensity (kg CO₂/kg) and specific strength on an Ashby-chart basis. CFRP exhibits the highest fatigue life at all stress levels and the lowest void content (1.8% at optimum 60 °C cure) but the highest CO₂ intensity (34.1 kg CO₂/kg). The hybrid composite achieves intermediate fatigue performance with a 31% reduction in CO₂ versus CFRP and ductility advantages in post-peak bending response. GFRP presents the most favourable cost-CO₂ position but exhibits earlier onset of matrix-dominated failure. TGA confirms glass transition temperatures of 138 °C, 126 °C, and 121 °C for CFRP, Hybrid, and GFRP respectively, with CFRP retaining the highest char residue.

Keywords: fibre reinforced polymer, fatigue, S–N curve, CFRP, GFRP, hybrid composite, ILSS, TGA, variable-amplitude loading, Ashby chart, specific strength, CO₂ intensity

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