Construction of equally stressed fibers trajectories in composite plates with holes to reduce the effect of stress concentration

The work is devoted to the effectiveness analysis of optimal curvilinear reinforcement in the area of holes. The developed technique for constructing curvilinear, biosimilar reinforcement structures with fiber placement along the principal tensile stresses trajectories is described. The proposed method for estimating the local volume fraction of fibers makes it possible to calculate changing elastic properties at each point of the composite plate during the iterative construction of fiber trajectories. The developed program creates curvilinear fiber trajectories in a composite plate with holes, taking into account the restrictions imposed on the fiber laying angle and the prohibition on intersections of trajectories with the hole and with neighboring fibers. The program, combined with the finite element method (FEM), allows to design curvilinear reinforcement structures that resemble the structure of wood fibers in the knot area. Based on the developed program, rational trajectories of fibers around the holes were constructed. It was shown that such reinforcement structures provide a noticeable decrease in the effective stress concentration factor, calculated taking into account an increase of fibers local volume fraction near the holes contour. This leads to an increase of bearing capacity of parts with holes and rivet attachment points. The influence of composite anisotropy degree and geometric parameters of hole system on the effectiveness of curvilinear reinforcement is investigated. The effect is higher the greater the degree of heterogeneity of the stress field.