Numerical study of GFRP joints bearing strength reduction due to drilling-induced delamination

Abstract

Delamination is one of the most common defects caused by drilling, which can have negative effect on the joint performance. This study investigates the effect of delamination on the bearing strength of [0/90]2s, [15/−75]2s, [30/−60]2s and [45/−45]2s GFRP layers numerically. Cohesive zone method and virtual crack closure technique have been used for delamination modeling and the results of these two methods have been compared. FEM results show good agreement with available experimental data. Results demonstrated that delamination reduces the bearing strength. Among four different stacking sequences, delamination has the most effect on the laminate with the stacking sequence of [0/90]2s. In both delaminated and non-delaminated models, [0/90]2s and [45/−45]2s stacking sequences have the most and the least bearing strength, respectively. By increasing the radius of delaminated zone from 3 mm to 15 mm, bearing strength does not change a lot. As the delaminated zone reaches the edge of the specimen, bearing strength reduces strongly because the layers separate completely and the load-carrying capacity reduces. A parametric study was also conducted to examine the effects of different factors. The results of parametric study showed that by increasing the volume fraction of the fiber as well as the use of carbon fiber instead of glass fiber, the bearing strength increases.