Integrative simulation chain for improved components design: linking mould filling and structural simulations

Computer-Aided Engineering (CAE) is currently a standard tool in the development process of automotive components. For thermoplastic parts, for example, the manufacturing process is usually simulated with injection moulding simulation software, whereas passive safety is simulated with explicit crash software. Today, these two computational methods are only linked in the simulation of fibre-reinforced thermoplastics, where process induced fibre orientation is used by crash simulation to predict mechanical properties. In this work, a computer-assisted engineering (CAE) product design workflow is proposed for high-fidelity performance predictions of unreinforced injection moulded components. This approach integrates material testing at the part level and injection moulding simulation (Moldflow), and subsequently imports these “as-moulded” simulation results directly into a finite element solver (LS-Dyna) for high-fidelity performance predictions. A newly developed dedicated computer application allows users to seamlessly use results from injection moulding simulations in crash simulations. The manufacturing boundary conditions that most influence the mechanical behaviour are combined through the thermomechanical indices (TMI) methodology and mapped onto each crash mesh element. Mathematical functions have been used to correlate the TMI to important mechanical properties of the moulded polymer. A user-defined material model can read those indices and translate them to local mechanical properties. To validate the method, different combinations of moulding conditions were selected to manufacture components that were subsequently subjected to impact tests. The mechanical response of the polymeric parts under crash was analysed by simulations and validated by experimental testing. A set of quasi-static (1 mm/s) and dynamic impact (3 m/s) tests were performed, and the force–displacement curves were both experimentally and numerically assessed. The simulations under quasi-static loads overestimate the attained peak force, but the overall material response (elastic and hardening) is very representative of the expected trend. In the case of dynamic loads, the crash simulations can predict realistically the overall force–displacement curves in complex moulded geometries.