ADVANCES IN LIQUID MOLDING FLOW SIMULATION: FABRIC AND DISTRIBUTION MEDIA COMPACTION AND TOW SATURATION

摘要

Liquid Composite Molding (LCM) processes comprise of closed molding processes in which the fiber preform is placed in a mold or on a tool and resin is injected into the preform to cover all the empty spaces between the fibers to produce a void free part. Resin Transfer Molding (RTM) and Vacuum Assisted Resin Transfer Molding (VARTM) are the two most well known processes that fall under LCM category. LCM flow simulation programs have been developed and are finding increasing use in order to gain a better understanding of the resin impregnation as well as to aid in optimizing manufacturing parameters as the part complexity and size increases. Also as new sub-classes of LCM emerge to address different manufacturing demands, there is a need to modify the model and/or the boundary conditions in the simulation to address the additional physics. Processes such as VARTM, RTM Light, and Compression RTM offer sufficient deviations from the more traditional RTM to warrant modification of the governing equations in the simulation. The use of flexible, non-rigid tooling in many of these processes causes the preform thickness to vary during the infusion due to the compaction and debulking of the preform. The compaction of the distribution media after the injection line is closed serves as a resin reservoir and helps fill the fiber tows which are partially filled. To incorporate this physics one must either alter the governing continuity equation, or find other appropriate modifications to capture these effects. The dual scale nature of the preform, in which the fiber tows fill more slowly compared to the bulk preform, increases the importance of the capillary effect in fiber tows and needs to be included. These effects are modeled and incorporated in our existing simulation software, Liquid Injection Molding Simulation (LIMS) and their significance is highlighted by identifying the important material and process parameters.