Predicting Material Defects in Reactive Polymeric Flows
Numerical modeling of forming processes involving the flow of chemical-reacting polymeric foams is very difficult because the flow kinematics is coupled with the thermal problem as well as with the polymerization and blowing reactions. The polymerization reaction increases the material viscosity and the expansion induces the material growing, generating a porous structure. When the polymerization takes place much faster than the foam expansion, the material becomes too rigid before the conclusion of the expansion. In this case the cellular walls can be broken with the associated consequences in the mechanical properties of the conformed pieces. On the other hand, when the foam blowing finishes before the complete polymerization, the low material consistency is not enough to preserve the final geometry, and the structure collapses when the expansion is finished. The numerical simulation can be used in order to determine a good compromise as well as to control the forming process to avoid other different defects.
Advection equation, flow front tracking, polymeric foams.