Cure Kinetics Modeling and Cure Shrinkage Behavior of a Thermosetting Composite

In this work, the cure kinetics and through-the-thickness cure shrinkage upon curing of a carbon fiber-epoxy composite (AS4/8552) were studied. The study is composed of two major parts. Firstly, dynamic and isothermal Differential Scanning Calorimeter (DSC) scans were performed to develop a new cure kinetics model. The most appropriate kinetic model that produces a nearly perfect fit of all data sets corresponds to a process with two single-step parallel autocatalytic reactions with diffusion control. Multivariate kinetic analysis was used to evaluate the parameters. In the second part of the study, the coefficients of thermal expansion (CTEs), the glass transition temperatures (T-g), and the through-the-thickness cure shrinkage strain values of the partially cured unidirectional and cross-ply composite samples were measured by using a dynamic mechanical analyzer (DMA). Cure strains were measured throughout the Manufacturer's Recommended Cure Cycle (MRCC) with the same method. Results indicate that glass transition temperatures of partially cured samples can be measured very closely by the two methods (DSC and DMA). The methods proposed were proved to be very reliable to predict the degree of cure and to measure the through-the-thickness strains during the cure cycle. POLYM. ENG. SCI., 50:84-92, 2010. (C) 2009 Society of Plastics Engineers