An investigation is performed to study the effects of friction on the three-dimensional (3D) stress state around pin-loaded holes in laminated composites. The composite pinned joints are modeled as a linear elastic contact problem with friction; therefore, the interactions between the pin with the laminate follow the law of Coulomb friction. An analytical solution for the 3D stress state involved in this problem is developed based upon the variational principle of complementary energy. Compared to the previous research based on a two-dimensional stress assumption, the present solution is innovative, since the out-of-plane effects (i.e., edge effects) near the pin-loaded holes are considered. The present formulations are restricted to the laminated composites with bi-directional fiber orientations, because all the traction and displacement boundary conditions can be satisfied in such type of laminates. Numerical results for pin-loaded cross-ply laminates with different coefficients of friction are presented. It is shown that the effects of friction on the magnitude and distribution of the 3D stress state around pin-loaded holes in laminated composites are significant.
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