The influenc e of the loading rate on the material behaviour of glass fibre reinforced phenolic composites and phenolic resin-impregnated aramid paper (Nomex ® ) honeycomb structures was investigated experimentally. The composite specimens were made of woven fabric plies and loaded in tension and shear. Two types of Nomex ® honeycomb specimens (hexagonal and over-expanded) were loaded in uniaxial compression in all three material directions. Quasi-static test results were compared to dynamic test data obtained on a drop tower, where different strain rates from 10 s -1 to 300 s -1 were tested.The glass/phenolic composite material showed a remarkable strain rate effect at higher loading rates with over 80% increase in tensile strength. Also for the Nomex ® honeycomb an increase of the stress level of up to 30% was observed. These material characteristics should be taken into account in case of dynamic analysis (e.g. crash, impact) of honeycomb sandwich panels for public transport applications, which are usually made from these phenolic materials.
The characterisation of the mechanical behaviour of folded core structures for advanced sandwich composites under flatwise compression load using a virtual testing approach is presented. In this context dynamic compression test simulations with the explicit solvers PAM-CRASH and LS-DYNA are compared to experimental data of two different folded core structures made of aramid paper and carbon fibre-reinforced plastic (CFRP). The focus of the investigations is the constitutive modelling of the cell wall material, the consideration of imperfections and the representation of cell wall buckling, folding or crushing phenomena. The consistency of the numerical results shows that this can be a promising and efficient approach for the determination of the effective mechanical properties and a cell geometry optimisation of folded core structures.
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