Cure process modeling and characterization of composites using in-situ dielectric and fiber otpic sensor monitoring

Liquid Composite Molding (LCM) techniques including the Resin Transfer Molding (RTM) and Vacuum Assisted Resin Transfer Molding (VARTM) are gaining significant importance for fabricating aerospace and automotive composite parts, owing to the low investment costs. During the curing process, the resin undergoes a property change due to cross-linking of polymers, where it transitions from the liquid state to the solid state. Further, during the cooling process, there is a change in the glass transition temperature, resulting in residual stress and strains. The residual strain and deformations accumulated during the curing of the resin at high temperatures result in significant challenges to the final part shape and performance of the composite structure. This research presents a thermo-chemo-mechanical curing model for liquid composite molding processes, which is validated with in-situ sensor monitoring data including viscosity, temperature, and degree of cure using dielectric sensors, and the distribution of induced strains during the curing process using distributed optical sensors. The viscoelastic curing model developed in ABAQUS constitutes of the resin cure kinetics, viscoelastic resin properties, and thermal and stress analysis components. A case study is performed for an angle bracket, where the resulting cure-induced stress deformation is observed and validated, and the spring-in angle of the bracket is predicted.