Modeling and numerical analysis of composite manufacturing processes.

Abstract

Resin Transfer Molding (RTM) and Structural Reaction Injection Molding (SRIM) are relatively new processes for high volume manufacturing of continuous fiber reinforced polymers. In RTM/SRIM, the mold is packed with dry fiber preforms that act as reinforcements. These preforms are impregnated progressively by the resin injected through the injection ports of the mold. After the mold is completely filled, the resin solidifies in the curing phase and the product is taken out of the mold. In this work, the process analysis of RTM and SRIM is given, which includes the mold flow analysis in the mold filling phase and the residual stress analysis in the curing phase. In the mold flow analysis, the governing equations are derived considering the actual flow field between the reinforcing fibers, to which the homogenization method is applied to give the averaged flow model. Using the model, a simulation program is developed based on the Finite Element/Control Volume (FE/CV) method. First, the mold flow through porous fiber preform is analyzed and the results are compared to those of other modeling methods. Then, the results are extended to the case of double porous fiber preforms. On the numerical side, the application of the adaptive finite element method to the mold flow analysis is investigated to enhance the computational efficiency. An adaptive remeshing routine is constructed and combined with the simulation program. The routine controls the mesh sizes during the simulation so that the finite element approximation error of each mesh are within prescribed error bounds. It is found that the adaptive remeshing method can significantly enhance the computational efficiency in the mold flow simulation. In curing, the residual stresses are developed due to the volume mismatch between the resin and the fiber. These stresses are modeled based on elastic analysis, and the homogenization method is utilized in the solution procedure due to the complexity of the material structure. The homogenized governing equations are solved using the finite element method, and the residual stress distributions within the microstructure are obtained for a woven fiber/epoxy composite part with complicated microstructure.