Observations of fatigue damage development in woven glass fiber-reinforced polymer composite using transmission light photography technique

Fatigue behaviour is an important aspect for consideration while handling glass fiber-reinforced polymer (GFRP) composites. A combination of (0°/90°) and (±45°) plies are gaining practical interest in engineering applications due to their excellent mechanical properties. Properties of individual above-stated plies primarily influence the behaviour of laminates. Fatigue behaviour of on-axis (0°/90°) and off-axis (±45°) fiber orientated woven GFRP laminates was investigated. Tensile and tension-tension fatigue tests were performed on the prepared test coupons according to the ASTM standard. Fatigue test was conducted until failure at maximum applied stress of 90%, 70%, and 50% of the respective ultimate strength. Damage growth was monitored in the term of debond zones by employing the transmission light photography technique. Testing process was recorded by using a digital camera. The results were established in terms of the stress-strain curve, Wöhler curve, debond zones and dynamic stiffness. The fatigue strength of off-axis laminates was much lower than the on-axis laminates. Global damage has occurred in (0°/90°) laminates while (±45°) laminate witnessed localized damage. At higher stress levels, samples were failed at shorter lifespan with aggressive damage; however, on-axis specimens survived with longer fatigue life.