Smart hybrid composite sensor technology to enhance the detection of low energy impact damage in composite structures

This paper introduces novel structural health monitoring (SHM) sensors to improve the detection of low energy impact damage in laminated composites. The sensor is a purposely designed thin-ply hybrid composite, composed of a layer of unidirectional S-glass/epoxy and another layer of unidirectional ultra-high modulus (UHM) carbon/epoxy. The sensor was incorporated onto both the impacted face and back of a substrate plate made from unidirectional T800 carbon/MTM49-3 epoxy prepregs with the stacking sequence of [45/0/90/-45]4S. A series of drop tower tests were conducted on the composite plates with and without the attached hybrid sensing layer, with two different in-plane dimensions and varying energy levels ranging from 3 J to 124 J. The results indicate that the sensors functioned satisfactorily and provided direct correlations between visible and internal hidden damage detected by C-scan. The sensor can be optimized by selecting appropriate material properties and adjusting it to the in-plane dimensions of the substrate.