In situ cure monitoring of composite materials in autoclave molding

Abstract

A real-time measurement of internal and residual strains in GFRP laminates with an extrinsic Fabry-Perot interferometric (EFPI) optical fiber strain sensor is performed in an autoclave molding. Another piezoceramic material is presented as a sensor for monitoring of resin curing. It is made of crystalline lead zirconate titanates (PZT) thin films synthesized by hydro-thermal method on titanium substrate. It is called PZT-S/A. Each sensor is embedded into pre-preg sheets before the molding. The ion viscosity and the temperature of the epoxy resin matrix are also simultaneously measured with a dielectric sensor and a thermocouple, respectively. The results of the experiments show that the internal and residual strains of GFRP laminates during the molding can be monitored by the optical fiber sensor. It is also shown that PZT-S/A is available for monitoring the curing state of the resin till the gelation point.