Reusable piezo-sandwiched PTFE film for in-process monitoring of advanced composites

Abstract

Environmental and cost-saving advantages derived from the use of composites attract aerospace and automotive industries as these materials offer significant structural and aerodynamic advantages over traditional metal structures. The composites industry, however, is concerned with the manufacturing processes as they cannot provide fast enough cycle time to match metal alloy processes. Our research aims to develop a sensing technology in the form of a reusable in situ cure monitoring and assessment system that can predict the formation of manufacturing defects and monitor the degree of cure. Thin-film material is chosen from various PTFE-based material by prioritizing the debonding effect and signal transmission through the composite part. Then, the film is used to sandwich piezoelectric actuators and sensors to monitor out-of-autoclave carbon fiber composite plates using ultrasonic Lamb waves by temporarily adhering to the manufactured part creating an effective electromechanical coupling between the sensing film and the laminate. Initial results, through the analysis of the fundamental antisymmetric A₀ mode at low frequencies, indicate that analyzing the velocity and amplitude of these waves over cure time determines gelation and vitrification points. Experimental results have also proved the feasibility of using such a reusable film for different curing cycles, always determining certain cure parameters.