Effects of composite lay-up configuration and thickness on the damage self-sensing behavior of carbon fiber polymer-matrix composite

The lay-up configuration (unidirectional, crossply and quasi-isotropic) and thickness (8–24 laminae) affect the damage self-sensing characteristics of continuous carbon fiber epoxy-matrix composites. The damage is by drop impact directed at the top surface of the laminate. The oblique resistance (i.e., resistance at an angle between the longitudinal and through-thickness directions) is an effective damage indicator for all lay-up configurations and thicknesses. The surface resistance of the bottom surface is an effective damage indicator for thin (8-lamina) composites, though it is less sensitive to minor damage than the oblique resistance. The surface resistance of the top surface is less effective than that of the bottom surface for 8-lamina multidirectional composites. The through-thickness resistance is an effective damage indicator for 16- and 24-lamina quasi-isotropic composites, but is ineffective for 8-lamina composites of any lay-up configuration. In general, effectiveness means a monotonic and significant increase of the resistance with damage extent.