Modeling injection molding processes with deformable porous preforms

This paper deduces a new model aimed at simulating injection molding processes under isothermal conditions. These processes can be generally stated as infiltration problems in initially dry porous materials. The spatial domain is then divided by the infiltration front into two time-dependent subdomains, the dry and the wet porous preforms, both being allowed to deform under the action of the liquid pressure. It is shown that the model calls for the definition of the stress-deformation relationship of both the dry and the wet preforms, which are assumed to behave elastically and inelastically, respectively. The coupled flow/deformation problem in the two regions (separated by an interface) is formulated with the corresponding boundary conditions and with the proper evolution equations determining the motion of the boundaries. The mathematical problem is solved numerically, highlighting the importance of inertial terms in the early stage of the infiltration and focusing on the influence of the mechanical properties of the material and on the deformation of the preform during the infiltration process.