Material Modeling and Finite Element Analysis of Hydroform - Short Glass Fiber Filled Thermoplastic Front-End Structures

Increasing use of engineering thermoplastics in the applications such as load bearing automotive components necessitates accurate characterization and material modeling for predicting part performance using finite-element simulations. Uniaxial tensile test data on glass filled thermoplastic resins exhibit highly nonlinear deformation with no clear demarcation between elastic and plastic regions. Hence, the estimation of modulus and yield stress values, required for the finite element analysis, is invariably through the subjective interpretation of the CAE analyst, which may not be consistent and unique. Use of parameters such as tangent modulus, yield stress and the post yield data calculated at 0.2% strain for finite element computations does not yield good correlations with experimental values. This paper outlines an alternate approach for evaluating material parameters for short glass filled engineering thermoplastics. The proposed approach had been applied to automotive hybrid front-end structures. This hybrid Hydroform - Plastic Structure (HPS) is a Pressure Sequenced Hydroform (PSH) tube over-molded to an injection molded engineering thermoplastic (ETP) panel. The plastic material used here is a Polyphenylene Ether / Polyamide alloy with 30 % short glass (PPO / PA / 30 % GF) reinforcement. The finite-element formulation took the plastic-steel interactions of hybrid structures into account. Results of the proposed approach validated through the experimental tests on the front-end structure are presented and discussed.