Approximate Interlaminar Fracture Envelopes for Unidirectional E-glass/polyester Composite

Abstract

In this paper an experimental study is performed in order to determine an approximate interlaminarfracture envelope of a unidirectional E-glass polyester composite. First, the pure mode-I fracturetoughness is determined by using the standard double-cantilever beam (DCB) specimen. Second,the pure mode-II toughness of the material is evaluated by means of the over-notchedflexure (ONF)specimen. Finally, the mixed-mode toughness is determined with the aid of the over-leg bending(OLB) coupon. Both the initiation and propagation fracture toughness are determined within theextended ranges of crack length. The fracture envelopes are determined by using the steady-statevalues of the fracture toughness at crack initiation and propagation. Two criteria are used to obtain theenvelopes: the traditional power expression and the physically more acceptable criterion by Williams.The results are compared with previous envelopes and similarity is established.