Fracture Mechanism of Polypropylene-Kenaf Composite under Cyclic Loading

Abstract

Mechanism of fracture of polypropylene composite reinforced by kenaf fiber under cyclic loading was investigated. Weight fraction of the composite used is 50% polypropylene and 50% kenaf fiber with random fiber orientation. Skins of composite that contains polypropylene dominant fraction are formed on both surfaces. The experiments were performed with flat specimen under cyclic flexural loading with constant displacement. Cyclic softening was detected by hysteresis loop of a local area. Deformation of the specimen was measured from the observed cycles. Fracture features were investigated using optical microscope and scanning electron microscope. The result shows that polypropylene-kenaf composite with 50%-50% fraction with random fiber orientation has complicated fracture features. The damage of the composite started from internal part. The surface crack proceeded after the internal damage. Moreover, it is discussed that some of fibers were covered by only thin matrix. The strength of specimen was determined the fracture behavior of fibers.