Numerical lamb wave modeling and analysis for cure cycle shortening of carbon fiber composites

Abstract

Advanced carbon fiber composites are renowned for their great tenacity as, although being thin, they provide great strength, keeping structures light in weight. The composites industry struggles with longer cure times when compared to other traditional material production. In this study, a computational model for a carbon fiber reinforced polymers (CFRP) plate is developed to imitate experimental monitoring of its cure cycle and degree of cure. The CFRP storage modulus is measured during the curing cycle with the aid of dynamic mechanical analysis, and its trend is incorporated into COMSOL combined structural and electrostatics multiphysics to replicate the same mechanical fluctuations during oven curing. Then, Lamb waves are excited and sensed via sandwiched piezoelectric transducers in a reusable Polytetrafluoroethylene sensing film to monitor the structural health of the structure. Minimum viscosity, gelation and vitrification are cure parameters observed from analyzing voltage and velocity curves of the A0 mode of the sensed signal. The cure cycle is trimmed, and the same cure parameters are shown offset by the 1 h deducted, proving that the numerical model is valid. Further analysis of the numerical voltage and velocity curves suggests an additional cure parameter defined as “gelation initiation” when compared directly to the experimental trends. Additionally, the decomposition of different wavefield modes is scrutinized to describe their scattering throughout the layered structure. Results show a new entrapped antisymmetric mode appearing inside the CFRP laminate at the start of the cure, which suggests that the previously studied A0 mode had been initially converted from the CFRP S0 mode.