A finite element unit-cell method for homogenised mechanical properties of heterogeneous plates

This paper presents a 3D unit-cell approach which enables estimations of all bending, in-plane and coupling properties in the sense of the classical laminated plate theory for heterogeneous plates. For this reason, periodic boundary conditions which simultaneously allow in-plane as well as bending/twisting deformation modes are introduced. In contrast to existing approaches, the 3D unit-cell is connected with the macroscopic plate theory by means of prescribed loads and the extraction of strains/curvatures. Novel bending experiments at large curvatures of E-glass-fibre/epoxy cross-ply laminate with cracking outer ply at the bending tension side are conducted. Subsequently, numerical results are validated by comparing them to the measured bending stiffness degradation. Further, the effects of the single-sided transverse cracks on relevant stiffness properties are computed.