Monitoring Through-The-Thickness Behaviour of Composites Using Fiber Optic Sensors

Abstract

A dynamic stress based theory for composite laminates that assumes a piecewise linear distribution of in-plane stresses across each lamina is developed. Unlike displacement based approaches this theory accurately predicts transverse stresses through the lamina thickness even in regions of high stress gradients such as free edge delamination coupons. To validate the accuracy of the transverse stresses predicted by the theoretical model, a novel experimental technique is being developed. The experimental program utilizes unintrusive extrinsic Fabry-Perot interferometric strain sensors (EFPI-SS) embedded through the lamina thickness to monitor the transverse normal stress/strain. This experimental technique is unique in that to the authors’ knowledge it is the first study of its kind to directly monitor through-the-thickness internal behaviour in multiply composite materials.