Modelling the core properties of composite panels based on woven sandwich-fabric preforms

A finite-element preprocessing program was developed to predict the mechanical performance of the cores of woven sandwich-fabric panels. These materials, which are produced from velvet-weave sandwich-fabric preforms, provide a new type of sandwich structure with a high skin-core debonding resistance and the potential for cost-effective sandwich construction. There is a large variety in possible core layouts and thus mechanical performance. To model the core behaviour a detailed geometrical modelling of the core lay-out of unfoamed panels was carried out. A unit-cell of the sandwich-fabric panel under consideration is determined and the shape of the piles and pillars and the resin distribution inside the unit cell are modelled. As inputs, only weaving data and some panel production parameters are required. The predicted microstructure for the cases which were modelled had a good resemblance to reality. For the FE analysis a homogenization principle has been used. Linear static analyses for the basic core properties (flexural shear and flat compression) have been performed. The results for the shear modulus as a function of the pile shape were very good. Model predictions at higher resin contents and for the compression modulus were less accurate.