Experimental, theoretical and numerical investigation of the drilling effects on mode I delamination of laminated composites

Abstract

Drilling is an obligatory operation to assemble the different parts of aerospace structures. To fabricate these structures, laminated composite systems have been extensively used. In the laminated composite systems, delamination is usually occurred. Hence, in this paper the effect of drilling on the mode I delamination of E-glass/epoxy laminates was investigated using experimental, theoretical and numerical methods. In the practical study, six different drilling conditions (hole with diameter of 2, 4 or 6 mm drilled at the distance of 10 or 15 mm from the delamination front) were chosen. Double Cantilever Beam (DCB) test configuration was used to characterize the mode I critical strain energy release rate (CSERR). Besides, since testing for each drilling configuration would be expensive, an analytical model was developed based on a Timoshenko beam resting on two-parametric elastic foundation. Moreover, to observe the distribution of CSERR along the delamination front, a finite element analysis was performed. It was resulted that the CSERR, its distribution and the R-curve are strongly affected by the drilling parameters. At the end, the analytical model was validated by the experimental results.