Tensile properties of variable stiffness composite laminates with circular holes based on potential flow functions

In this study, a new type of variable stiffness laminate combining the curving path planning with the potential flow theory was experimentally investigated. By a reasonably discrete pair of mutual conjugate functions, contour curves in the flow function and potential fields were generated individually. According to these, the narrowband fiber tracks on the two variable stiffness plies were individually defined. On each intersection of the two plies, the tracks were mutually orthogonal and played a key role in improving the properties of the laminate. The tensile tests of the laminate with central holes show that the ultimate tensile load and elastic modulus of the variable stiffness laminate increased by \({\sim }129\) and 110 %, respectively. The curving paths were effective in delivering stress from the area around the hole to the edge regions of the specimen. The path planning method was based on the flow function, and all the tracks on the entire ply were defined as a whole and thus may significantly benefit the subsequent studies such as parameter optimization of scalar function and the structure of the variable stiffness laminate. The analysis of the experimental data and fracture morphology comparison indicates that the tensile property of the laminates is significantly enhanced.