Buckling performance of curvilinearly grid-stiffened tow-placed composite panels considering manufacturing constraints

Tow-placement machines are able to fabricate variable-stiffness composite panels with curvilinear stiffeners. In this paper the buckling performance of curvilinearly grid-stiffened composite panels subjected to in-plane compressive loads under various boundary conditions is addressed. A Python-Abaqus script is developed to perform the buckling analysis of the panels. The skin is modelled using shell elements and the grid stiffeners are idealized by beam elements. Different design tailoring scenarios for grid-stiffened and unstiffened constant-stiffness and variable-stiffness skins are presented to demonstrate the influence of the stiffness variation created simultaneously by both the layout of the curvilinear stiffeners and by the fiber orientation variation of the skin on the buckling capacity. It is shown that the buckling resistance of the grid-stiffened quasi-isotropic skins can significantly be improved using curvilinear stiffeners compared to their straight design counterparts. A much higher degree of improvement can be achieved by concurrently tailoring both the skin and the stiffeners using curvilinear fibers. In order to guarantee the manufacturability of the designs, manufacturing constraints in terms of maximum curvature along the fiber and stiffener paths are imposed. It is demonstrated that imposing these constraints has negative effects on the buckling load improvement obtained for designs without considering manufacturing constraints.