Resin transfer molding (RTM) of advanced materials for high performance applications was investigated. An integrated and systematic study was conducted to characterize representative resins and fibers designed for aerospace RTM composites. The material property data base and constitutive models were incorporated into a numerical modeling program for simulating RTM. Experimental molding results were compared with numerical simulation to verify the models. The influence of the mold material on heat transfer, resin curing and composite properties was also investigated.
Analytical instruments were used to characterize two advanced RTM resins. Two kinetic models were developed for a commercial RTM amine cured epoxy resin system. The first approach used a piecewise kinetic model to describe the observed reaction behavior. The second approach developed a parallel kinetic model which accounted for the individual contributions of two amines in the reacting system.
A viscosity model was developed for the amine cured epoxy which accounted for temperature and conversion dependence. A kinetic model and viscosity model were developed for a commercial bismaleimide (BMI) resin. The kinetic model accounted for the diffusion control of the reaction. The viscosity models and the kinetic models were incorporated into a numerical program for simulating resin transfer molding.
Debulking equipment specific to tackified fiber reinforcements was designed and set up. Permeability equipment was modified to study tackified fabrics at high temperature. The influence of debulking time was compared for two different tackifier binders.
Experimental molding examples were compared with numerical simulation of RTM. Simulated flow times for radial flow of epoxy resin into an 8-HS graphite fiber stack were compared with the experimental flow times. Simulated mold filling times were compared with the experimental flow times for unidirectional flow of a BMI resin into the 4-HS tackified graphite preform. Measured and simulated temperature peaks due to reaction exotherm were compared with each other.
An investigation of five alternative mold materials for RTM illustrated the influence of the tool material on heat transfer, resin cure, composite properties and temperature controllability.