Failure Characterization of FRP by Scanning Electron Microscope Technique

Abstract

Fiber-reinforced composite materials are used extensively in stiffness critical, weight sensitive structures such as those found in aerospace and motor racing. They are characterized by high inplane strength, stiffness and toughness and low density. The environmental effect on the FRP (fiber reinforced polymer) and the subsequent failure has lead to emphasize on the study of different fracture surfaces and their different modes of propagation. Delamination between layers is an important problem in applications of fiber reinforced composite laminates. This paper describes an experimental study to characterize the crack surface, crack origination and their propagation using scanning electron microscope (SEM). By observing carefully the fracture surface of the composite the factors affecting their respective failure and the type of environment they were subjected to could be determined. SEM micrographs of the fractured surfaces of carbon/epoxy and glass/epoxy composites revealed the failure modes (delamination sites, debonding, fiber pullout regions, crack propagation front, shear cups, hackles, striations, bubble bursting in the matrix).