Compression Molding of Reinforced Plastics Using the Element Free Galerkin (EFG) Method

Abstract

Abstract Composite materials using long fiber-reinforced plastics have seen increased usage in recent times due to their lightweight and better energy absorption characteristics. Compression molding, a high-volume, high-pressure method suitable for molding complex, high-strength fiberglass reinforcement plastics has been widely accepted in the manufacturing industry as an efficient process to mass-produce complicated shapes in a short time. Hence, it is of paramount importance to make this manufacturing process cost-effective and environmentally sustainable. To accomplish this, it becomes very important to understand different behaviors such as the fiber orientation, deformation, axial forces acting on the fibers, stresses occurring in the matrix, punch reaction force, etc. and the use of simulation-led design can help accomplish this with a high degree of accuracy. Considering the extreme high-pressure conditions that the reinforced plastics are subjected to, traditional finite element (FEM) numerical approaches tend to fall short when it comes to compression molding primarily due to severe mesh distortion. In this context, the EFG method has been considered in the current work. EFG, like FEM, is a spatial discretization method however is based on a particle-based approach. The domain of interest is decomposed into material particles and the support domain uses polynom functions to approximate field variables similar to the shape functions used in FEM. Additionally, a background mesh is typically used to integrate the weak forms for the momentum balance. A combination of this theoretical background of EFG, which minimizes the inherent mesh distortion limitation encountered in FEM, coupled with the ability to handle reinforcements and an adaptive mesh refinement method makes this approach suitable for compression molding applications. In this work, an approach to simulate the blank compression with and without fiber reinforcements using the EFG method has been presented. A separate implicit analysis was also carried out to calculate the spring back state of the non-reinforced model to identify the locations of the residual stresses. A 5-layer fiber-reinforced model with an orientation of [0/-45/90/45/0] was embedded into the matrix and the effect of the coupling behaviors between fibers and the matrix on the end deformed shape has also been studied. Primarily, the effect of having no axial resistance for the slip of the fibers versus defining a user-defined slip criterion on the wrinkling behavior has been compared. The approach presented in this work has shown great promise in simulating the compression molding of long fiber reinforced plastics.