Fracture analysis in 5HS carbon composites subjected to pure modes I and II fatigue induced delamination

Abstract

Interlaminar fracture process in woven composite laminate in general takes place in a nonlinear front propagation when analyzing a 2-D propagation for mode I opening. The nonlinearity is justified by the arresting crack at the warp yarn. Regarding mode II opening, the crack interaction to the crimp surface still needs further assessment. The tortuous crack path and, consequently, loading directions on both modes were determined in this work by fractographic analysis of quasi-static and cyclic loading fractured in 5HS carbon/epoxy composite specimens. The crack growth rate and strain energy release rate were compared to the fractographic images that approximately pointed out the driving force in each delamination stage. Mode I fracture surface showed to have more influence on fracture toughness (GIc) than amplitude loading while mode II fracture surface suggested the opposite behavior, all based on the well-known fracture patterns established along the years for other composite architectures.