ISE is currently developing a robust method for the determination of structural defects within laminated composite aerospace structures. The current method under development uses a mathematically derived specially-orthotropic lamination model subjected to sensitivity perturbations from empirically-derived dynamic transfer-function data.
Predicted failure areas, precipitated by a decrease in signal coherence between test points, and an increase in the residual modal forces are screened under a statistical failure model using the maximum strain energy (Beltrami) theory and maximum distortion energy (von Mises) theory as indicators of areas of delamination of plies, disbonding of joints, or void detection.
Currently an en engineering proof-of-principle exercise, ISE hopes to adapt the method ultimately into an onboard damage detection monitoring system for in-flight aircraft. The photo to the right shows one of the many tests being performed to quantify the extent of disbonding and delamination within an eight-ply woven composite panel specimen having a NASA ply configuration of [0/45/0/-45]S and an EA-956 resin.