Optimization design for hole geometries and fiber steering of composite laminates with a hole

The objective of this study is to use numerical simulation for investigating the effects of hole geometry and fiber steering on the strength of a carbon fiber reinforced plastic (CFRP) laminate with a hole. For the 0° layers of CFRP laminates, the fibers were aligned to the maximum principal stress direction under uniaxial tensile loading to simulate a curved (steered) fiber orientation. Using Bézier curves, 600 CFRP panel models with different hole geometries were generated. Then they were subjected to progressive failure analysis and buckling eigenvalue analysis under tensile and shear loading, respectively, for the quasi-isotropic (QI) and fiber-steered models. A genetic algorithm (GA) was used to perform a multi-objective optimization design with tensile strength and shear buckling load as objective functions. Results show that the curvilinear orientation of the fibers near the stress concentrations was effective for strength enhancement. For example, for a panel with a rhombic hole shape with no curvature at the hole edge, the strength enhancement effect of fiber steering tends to be considerable under both tensile and shear loading. Results show that a multi-objective optimal design can search for a hole shape that has 0.132–1.41 % higher strength than an elliptical hole under both tensile and shear loading.