Analysis on the compression molding of carbon fiber-epoxy composite

Abstract

Carbon fiber reinforced plastic are prepared by compression moulding technique, using epoxy resin impregnated prepregs. The most critical part of the process is the pressing time, i.e., the time between placing the loaded mould onto a heating plate and applying the pressure to close the mould. If pressure is applied too early, too much epoxy was exuded from the mould and there is higher resin shrinkage during curing. If pressure is applied too late, entrapped air and gases are less likely to escape from the mould. These phenomena are related with the viscosity change as the degree of the curing reaction increases and affect void content of the composite. A systematic analysis on the compression moulding process was done by evaluating the curing reaction processes and the viscosity change during the compression moulding process. The epoxy curing reaction kinetics were determined by a dynamic Differential Scanning Calorimetry (DSC) method on a epoxy resin-nadic methyl anhydride (NMA)-benzyl dimethyl amine (BDMA) system. The viscosity change at dynamic curing condition was measured by Rheometrics Mechanical Spectrometer (RMS) and Dynamic Mechanical Analyzer (DMA). The correlation between the degree of curing and the viscosity was obtained from kinetics and empirical viscosity data through a multivariable non-linear regression. A simulation model was established so that one can predict the optimum pressing time at a given optimum viscosity point for the compression moulding.