On the improvement of analytical delamination model for drilling of laminated composites using Galerkin method

摘要

Despite the fact that fiber reinforced polymer composite laminates have high strength to density ratio, they have machinability limitations. Drilling operation is one of the mostly used machining processes on the laminated composites as it plays a significant role on assembly of composite parts. The most critical damage, affecting drilled composites, is delamination. Using Galerkin method, this paper, proposes a new model, removing most of the assumptions of previous models. The result of this study can be used to precisely and more reliably predict the critical thrust force-feed rate at which delamination could occur. The model uses the results of cutting theory to predict the distribution of the drilling load on delaminated area, a modified variety of Mindlin-Reissner plate theory in conjunction with the linear elastic fracture mechanic theory in mixed mode loading condition for the prediction of critical thrust force. Comparing with the previous proposed models, it has no assumptions for the load distribution and it considers mode I and mode II simultaneously for the growth of the delaminated zone, which makes it possible to consider non-uniform loading conditions of the drilling process. Using this model, the effect of the distribution of the drill force on the composite is investigated. The critical thrust force was studied for load-controlled and displacement-controlled loading conditions. For the experimental validation, the onset of the growth of the crack was detected using acoustic emission. The results of the experiment were compared with that of model.