Curvature-controlled trajectory planning for variable stiffness composite laminates

Abstract

Variable-stiffness laminates can redistribute the applied load and increase critical buckling loads compared to traditional straight fiber laminates. To take full advantage of fiber reinforced composite materials, a practical trajectory planning method is generated based on the maximum principle stress vector field. A reference path is represented as a blend curve of a sequence of uniform cubic B-spline segments passing through some given maxi-stress points. Based on the local-support property of each B-spline segment, subsequent paths within single lamina can be easily obtained by shifting the reference path along a specific direction. A fast localized curvature-correction algorithm is proposed to control the curvatures of the reference path and strictly constrain the void gap or overlap in a variable stiffness lamina. This trajectory planning method takes the requirement of automated fiber placement machines into account, and improves the mechanical properties of the variable stiffness composite laminates by decreasing the occurrence of gap-errors, such as buckling and wrinkling between adjacent paths. A practical case of variable stiffness trajectory planning is provided to demonstrate the feasibility and efficiency of the proposed method. In this practical case, the gap-error rate has decreased from 45.8% to 4.2%.