An experimental investigation of fatigue performance and damage distribution mechanism in Bi-Directional GFRP composites

• Published in: International journal of fatigue 2025-04, Vol.193, p.108735, Article 108735
• Main Authors: Khan, Ateeb Ahmad, Singh, Indra Vir, Mishra, Bhanu Kumar, Chennamsetti, Ramadas
• Format: Article
• Language: English
• Subjects: Bi-directional GFRP composites; Damage Distribution Mechanism; Stiffness Degradation; Tension-Compression Fatigue; Tension-Tension Fatigue
• ISSN: 0142-1123
• DOI: 10.1016/j.ijfatigue.2024.108735

•Effect of mean stress, gauge length and surface roughness is investigated on the fatigue life of bi-directional GFRP.•Transverse fibres mitigate micro-buckling of longitudinal fibres, achieving comparable compressive and tensile strength.•Fatigue strength has been determined for one million cycles at different stress ratios.•Fractographic analysis demonstrated the effect of stress levels on failure mechanisms.•Fatigue damage progression mechanism has been analysed using IR scans. This study presents an experimental investigation of the fatigue performance and damage distribution mechanism of bi-directional GFRP composites. Uniaxial fatigue tests have been conducted under load-control, at stress ratios, R = 0.1, 0.5 and critical stress ratio (χ=-0.9). The influence of gauge length and surface roughness on fatigue life has been examined for R = 0.1. An infrared (IR) camera is employed to monitor temperature evolution and capture thermal images during the fatigue experiments. Fatigue stiffness degradation, energy dissipated per cycle, and severity of damage progression have been analyzed to elucidate the effects of stress levels and mean stress on fatigue performance. At higher stress levels, the damage is intense and localized, resulting in relatively shorter life due to fiber-breakage accompanied by rapid fatigue stiffness degradation. At lower stress levels, the damage is uniformly distributed and less severe, primarily involves stress concentration, resulting in longer fatigue lives. The study highlights the contrasting damage progression mechanisms for tension–tension and tension–compression fatigue. Under tension–tension fatigue, an oval-shaped damage zone forms perpendicular to the loading direction indicating transverse crack propagation, while under tension–compression fatigue, the damage zone aligns parallel to the loading direction indicating longitudinal crack propagation due to compressive loading.