Investigation of Ductility and Damage Behavior of C/GFRP Composite Laminates under Bending Loads

Carbon and glass fabric reinforced polymer (C/GFRP) composites are extensively used in aerospace and sports industry because of their exceptional properties. However, during service, static and dynamic bending loads can ensue damage in composites affecting their strength, stiffness and energy absorption. Carbon fiber composites, being inherently brittle, are prone to sudden catastrophic fracture without ductile-like behavior of metals. This study investigates mechanical behavior and damage mechanisms of woven C/GFRP composites in on- and off-axis orientations during bending. Initially, bending tests with quasi-static loading were performed, followed by dynamic ones using an Izod impact testing apparatus. Results showed distinct behavior in on-axis CFRP laminates with brittle fracture. Off-axis CFRP samples and both on- and off-axis GFRP laminates showed signs of damage and non-linear behavior, yet they retained their ability to bear loads. Significantly, off-axis specimens of both types and on-axis GFRP laminates exhibited enhanced energy absorption capabilities without experiencing fracture, undergoing pseudo-ductile deformation. CFRP specimens were analyzed with micro-computed tomography (micro-CT), provided insights into prevalent damage modes such as matrix mircocracking, debonding of tows, delamination and breakage of fabric. While on-axis CFRP laminates experienced brittle fracture, off-axis specimens exhibited a ductile-like response attributed to matrix plasticity, cracking and fiber trellising before eventual failure.