Cure strain monitoring in composite laminates with distributed optical sensor

Abstract

Measuring the strain history in pre-impregnated thermoset composites during the curing process provides valuable data for manufacturing specification development, quality control, diagnostics of dimensional stability, and validation of cure models. Distributed Optical Sensors (DOS) provide information along the entire optical path length of the sensor embedded in the laminate and present a promising high-resolution sensing option for in-situ strain measurement. This study’s contribution to the field is the coupling of the optical sensor monitoring of composite cure strain with models of the cure kinetics, viscosity, and glass transition temperature of the thermoset matrix. A unidirectional (UD) laminate and a structural laminate (SL) were manufacture embedded with an optical sensor. The internal residual strain developed during each stage of the thermal cure cycle is examined for both laminate types, including after cooling, and the models of the resin’s physical property development were used to facilitate interpretation of the strain measurement data from the DOS.