Insight into damage initiation and progressive failure in a nylon 6/agave fiber composite: A micromechanical modeling approach

• 3D FEA accurately predicts ductile failure in Ny6/agave fiber composites. • Matrix cavitation initiates damage in fiber–free zones and fiber–matrix interfaces. • Stress mode shift causes debonding around mid–sections of transverse fibers. • Multiscale analysis links microstructure to progressive and catastrophic failure. Damage in composite materials is difficult to capture experimentally due to the rapid evolution of failure at the microscale. Identifying the failure root cause is essential for improving material design. This study investigates the operative damage mechanisms in a nylon 6 composite reinforced with Mexican agave fibers (Ny6/AF) using 3D micromechanics–based finite element analysis (FEA). The model incorporates nonlinear constitutive behavior of both matrix and fibers and reproduces the experimental stress–strain response with a maximum deviation of approximately 4%, providing micromechanical interpretation of previously reported experimental observations. The results show that ductile damage is governed by matrix cavitation initiated in fiber–free regions and near the fiber–matrix interphase under negative hydrostatic pressure. Subsequent interfacial damage and strain localization develop preferentially around misaligned fibers, promoting void growth and stress redistribution toward longitudinal fibers. The progressive evolution of cavitation, interfacial damage, and localized ductile fracture leads to formation of critical defect configuration associated with the onset of macroscopic failure. These findings provide new micromechanical insight into damage initiation and progression in bio–based fiber–reinforced thermoplastic composites.