Strain rate effects in phenolic composites and phenolic-impregnated honeycomb structures

The influence 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.