Computer-aided design for dimensional stability of injection molded fiber-reinforced polymers

New exercises were developed for a senior level composites processing class with the help of Moldex3D software "e-design" modules to illustrate computer aided process design for injection molding of short fiber reinforced polypropylene parts. This class combines laboratory measurements and lectures on problem solving related to extrusion, compression molding and injection molding of both thermoplastic and thermosetting compounds. The emphasis in these problems was on dimensional stability and fiber orientation with different part geometries - a center gated disc and an edge gated rectangular plaque. Sixty students enrolled in the class were grouped into teams of three for this problem set. The geometry and mesh were generated and made available to the student teams. Two tutorials were also run to demonstrate the use of the software with readily available meshes to the students. By changing different parameters such as fill time, pack time, polymer type and fiber content, students could visualize these changes in the molded part dimensions and shape. Part quality was then estimated using parameters such as overall shrinkage and warpage. Students were also able to directly compare the simulated disc to an actual injection molded disc from a similar mold. The advantage of the simulation exercise was in helping students to visualize flow fields during injection as well as understanding the effects of various parameters on the final part dimensions. This visualization was a strength of Moldex3D as students were able to generate detailed contour plots and graphs along with videos to fully understand the processing stage for polymer composites. Using these visualization tools, each student team was able to evaluate and summarize how incorporating glass fibers into a polymer matrix affected the shrinkage and warpage of the molded part. Student responses were gathered to a survey questionnaire on their learning experience with the computer-aided design exercises.