Fracture Behavior of a 3-D Braid Graphite/Epoxy Composite

Abstract

An exploratory study of the fracture behavior and notch sensitivity of a 4-step, 3-D braid-reinforced graphite/epoxy composite has been made. Test methods based on the Mode I compact tension specimen were developed and lower bounds for the damage initiating force and the work of fracture were determined for certain notch-to-braid axis orientations. These values are higher than for laminate composites but showed severe anisotropy. Complementary in-situ and post-mortem optical and scanning electron microscopy were used to identify microstructural failure controlling features and to develop a volume-to-surface structural mapping strategy useful in accounting for some of the observed features of the failure process.