Experimental study of the low-velocity impact behaviour of primary sandwich structures in aircraft

The susceptibility of sandwich structures to localised (impact) damage is one of the main reasons why the sandwich concept is not yet used in large primary aircraft structures of airliners. The objective of this work is to experimentally investigate the damage tolerance of representative composite sandwich panels for primary aircraft structures. Instrumented low-velocity impact tests were performed on sandwich specimens consisting of carbon Non-Crimp Fabric/epoxy facings and a Rohacell (PMI) foam core. Both internal and external damage resulting from these impact events was evaluated.The foam core material has a considerable influence on the amount of damage detected by ultrasonic TTU C-scan. CAI tests however showed that this core damage has no significant influence on the residual compressive strength of the specimens.