Effect of fiber orientation and residual stresses on the structural performance of injection molded short-fiber-reinforced components

The increasingly need of lightweight structures in different sectors is driving new researches about the substitution of metal with polymeric matrix composite. Objective of this work is to optimize the strength design of short-fiber injection molding manifold block, originally made with brass, with the aid of a three-dimensional flow and structural analysis simulations. These Finite Element Analyses (FEA) were based on orthotropic, linear and elastic models including process-induced residual stresses. Through an appropriate interface, the results of injection molding analysis of 35 wt.% fiber reinforced polyphthalamides (PPA) manifold block are transferred to the structural analysis software. Autodesk Moldlfow software was used to predict the fiber orientation and the in-cavity residual stresses considering the flow kinetics and moulding parameters. The Abaqus interface for Moldflow was used to translate this data into a form that can be used for the structural analysis. Finally, this paper reports some experimental tests carried out on the injection moulded component in order to evaluate the internal burst pressure values. The results not only highlighted the importance of carrying out structural simulations, which consider both the orientation of the glass fibre and the residual stresses given by molding, but also showed the usefulness and accuracy of an integrated CAD-FEA approach. The application on a real case demonstrated good agreement with numerical analysis predictions.