Dealing with Nap-Core Sandwich Composites: How to Predict the Effect of Symmetry.

The behavior of nap-core sandwiches was investigated with a special focus on the effect of symmetry in nap cores. A nap-core is, in general terms, a 3D-formed hollow structure made of knitted textile impregnated by a thermosetting resin. The molding process determines if the nap-core is double-sided (symmetric) or single-sided. The sandwich with nap-core owns various remarkable properties of a novel lightweight material, but the nap-core's complex structure makes the prediction of these properties a difficult task. While the analysis of a single-sided nap-core sandwich has been presented by the authors before, this study is focused on the simulation of symmetric nap-core sandwich. Overall, performance of the structure is examined with respect to several loading conditions. The simulation approach invokes a typical homogenization scheme to find the engineering properties of the nap-core's fabric with least computational time and memory resources. Results from experiments and simulations exhibit a good compatibility, which prove the fitness of the modeling method.