Structural analysis of fiber-filled plastics with moulding process induced anisotropy

Thermoplastics have many advantages over metal parts, including lower mass and ease of fabrication. To further improve their elastic modulus, creep resistance, and dimensional stability, short fibers are added to polymers. Such composites find widespread use because they can be processed with techniques used for unfilled polymers, provided the fiber length is below a certain limit. However, the application of fiber-filled thermoplastic materials has been limited in many cases by the inability to accurately predict performance and durability.

In this work, structural analysis capability of ANSYS is used in conjunction with flow simulation capability of Moldflow. The Moldflow fiber orientation simulation model allows significantly improved prediction of orientation of fibers in a molded component over a range of polymer materials and fiber contents. The ANSYS interface for Moldflow is used to translate this information to an input file for structural analysis using ANSYS. With effect of fiber orientation incorporated in the material properties, results of this structural analysis provide more realistic valuse of deformation and stresses in the formed part.

Linear orthotropic analysis is carried out on ash tray door component by coupling Moldflow with ANSYS. A comparison is made between the results from linear isotropic and linear orthotropic analysis with different gating systems to understand the effect of these parameters on the mechanical performance of the part. Simulation results are able to predict the observed mechanical behaviour of short-fiber filled plastic components when the anisotropy of the material is taken into consideration. Traditional approach of treating the material property as isotropy overestimates the stiffness of the part. Also, modelling of flow is able to quantify the anisotropy generated in the part during its fabrication process.