A Nonlinear Analysis of the CLS Specimen

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Abstract
A nonlinear analysis of a cracked lap shear (CLS) specimen was carried out based on the theory for tie rod problems. The specimen in this case was an unidirectional Ciba Geigy T300/914 laminate with orientation and layup of (0°)9 at the thick section and (0°)5 at the thin section. In the tie rod analysis the CLS specimen was modelled as two beams joined eccen trically with the joint at the crack tip. The analysis gave the distribution of bending moments and shear forces along the CLS specimen, the deflection of the CLS specimen and the total energy release rate ( G) associated with delamination growth. The energy release rate was found to be independent of the crack length except for long crack lengths. In order to separate the mode I and mode II contributions of the energy release rate, bend ing moments and shear forces were calculated at a distance from the crack tip. The cross- sectional forces and bending moments were thereafter used as prescribed loads in a linear finite element analysis of a short section containing the crack tip. Using a crack closure scheme, the mode I ( GI) and mode II ( GII) energy release rates were calculated. The agreement in total energy release rate calculated from the tie rod analysis and the finite element analysis was good.