Experimental investigation on Mode Ⅰ interlaminar fracture behavior of laminated flattened-bamboo composite measured by VIC-3D technique

Abstract

Mode I fracture tests, with loading perpendicular to the grain and crack propagation parallel to the grain, were performed on 10 groups of laminated flattened-bamboo composite (LFBC) specimens using the compact tension (CT) method, and crack extension was monitored by VIC-3D (video image correlate, 3D) technique. Nine of the groups were interlaminar (RL) fracture considering specimen thickness (B) and initial crack length to width ratio (a/W), and one group was standard specimens for intralaminar (TL) fracture as a control. It was shown that the failure mechanism of TL fracture was fiber fracture and ground tissue damage, while RL fracture was adhesive failure accompanied by a small amount of fiber fracture. The difference in the failure mechanism determined the uncertainty of crack extension in RL, while the crack extension in TL was continuous. On this basis, different forms of load-displacement curves and load-crack curves were analyzed. In addition, a/W had no effect on the fracture toughness of RL, while the condition value of fracture toughness gradually increased and reached stability with increasing thickness B. The RL fracture toughness of LFBC obtained from the test was 20.8 MPa·mm1/2. The tensile strain field during crack extension was always concentrated at the crack tip, while the compressive strain appeared at the bottom of the specimen. An empirical equation for predicting the critical load of RL fracture was proposed by fitting to the test data.