Numerical simulation of strongly non-isothermal compression molding flows

Compression molding is an important processing technique for polymers and composite materials. Usually, a thermosetting molding compound is squeezed between heated dies; the squeezing flow fills the mold, and heat from the mold initiates the curing reaction. There is considerable interest in simulating this process for non-trivial geometries for the purpose of optimizing the design and manufacture of parts. A two dimensional finite element model was first developed to investigate how the transverse viscosity gradient affects the velocity profiles. Using a three dimensional finite element model with stratified viscosities and an approximate flow front advancement scheme, the filling pattern was calculated for a rectangular charge. In order to know how severe the nonisothermality is in the real compression molding process, a conduction-convection heat transfer analysis was performed. The heat transfer analysis along with a relation between viscosity and temperature was then incorporated into the flow simulation to see how operating conditions affect the filling pattern.