Abstract

For testing and analysing crack propagation under fatigue loading, crack onset precedes any crack growth. In this work, crack onset during the testing of Double Cantilever Beam (DCB) specimens is studied. The insert cycle experiments provide an experimental reference for our analysis using finite element methods. The insert cycle is analysed using three different methods, which are the Virtual Crack Closure Technique (VCCT), Cohesive Zone Modelling (CZM) and a combined method. In the combined method, the crack onset is modelled using CZM and propagation using VCCT. In other words, we strive to model the crack nucleation phenomenon in the adhesive bond of DCB specimen.

Abstract

The purpose of the present study is the evaluation of the bending-twisting coupling effect in the analysis of the DCB test by means of the analytical determination of the energy release rate of angle-ply laminated composites. The aim is to extend a previous work done by the same authors to new laminate configurations. Angle-ply laminates with symmetrical arms are analyzed, since in this case the application of a bending moment by means of the piano hinges causes a torsional rotation in each of the arms. That torsion is prevented by the hinges, due to the configuration of the test. Therefore, there is a non-uniform load distribution applied by the hinges, whose resultant is the applied load P and the resultant moment is an unknown twisting moment mt, which prevents rotation at the point of application. The resolution of the resulting system of forces and moments allows obtaining analytically the energy release rate, and analyzing the terms due exclusively to the bending-twisting coupling.