Three-dimensional resin transfer molding: Isothermal process modeling and explicit tracking of moving fronts for thick geometrically complex composites manufacturing applications - Part 1

In resin transfer molding (RTM) process modeling, current practices involve d in the simulation of resin impregnation through porous media have been ge nerally restricted to two-dimensional formulations based on Darcy's law for flow through thin cavities due to the increased computational demand and s tringent stability restrictions of the traditionally employed explicit fini te element-control volume (FE-CV) type approaches. The presence of multiple fiber layers in thick composites, or the notion of introducing impermeable inserts inside the fiber bundles to serve as protective armor, causes the resin impregnation to be a three-dimensional flow. This paper describes ful l three-dimensional simulations based on an explicit FE-CV technique to ass ess the practicality and suitability of the approach. Though viable, the te chnique treats the transient mold filling problem as a series of quasi-stea dy state problems. Additionally, an effective alternate form and discretiza tion of the field variables based on a flux-based finite element representa tion is presented in conjunction with the above primarily to illustrate the theoretical developments for general situations. For linear situations, th ey readily revert exactly to the traditional finite element representations . In part 2 of this paper a transient computational methodology eased on a pure implicit finite element method for applicability to three-dimensional RTM flow modeling is presented to demonstrate the improved effectiveness of the approach. The objectives of the efforts (part I here and part 2 in thi s issue), besides providing a clear understanding for flow in thick composi tes under isothermal conditions, are simply to (I) describe and investigate the traditional developments for practical geometrically complex three-dim ensional composite sections, (2) describe extensions of our previous effort s and provide effective avenues for handling three-dimensional thick compos ites, and (3) contrast the two approaches and explore the pros and cons for practical three-dimensional composites process modeling.