Effect of distribution of fiber volume fraction and resin-rich layer through thickness on stiffness of composite lattice structures

Cylindrical composite lattice structures used in space launch vehicles should resist allowed deformation and buckling under compression. Buckling and compressive global stiffness can be predicted using the mechanical properties of used materials; however, they can be changed by non-uniform distribution of the fiber and matrix in the cross-section of the structure. In this study, a cross-section of a rib extracted from a composite lattice structure fabricated by filament winding was prepared, and the fiber volume fraction and resin-rich layer were observed along the thickness direction. The variation in the stiffness matrix induced by the non-uniform fiber volume fraction and resin-rich layer was examined. A finite element model of cylindrical composite lattice structure with different diameter and thickness was used for buckling analysis considering the resin-rich layer. The variations in the critical buckling load due to the resin-rich layer were examined. Considering the characteristics of the cross-section from the manufacturing process of the actual structure, such as the distribution of fiber volume fraction and resin-rich layer, it was confirmed that the stiffness and buckling performance of the structure can be changed.