Modelling of ageing and optimization of composite structures
Andrzej Młyniec, Tadeusz Uhl
Quarterly No. 2, 2011 pages 180-184
DOI:
keywords: composite ageing, DFSS, FEM, product durability
abstract A study of the impact of Short Fibre Reinforced Polymer Composite degradation, based on a PBT matrix, on injection moulded snap geometry is reported. A nonlinear transversely isotropic material, taking into account the material ageing time, along with implemented failure criteria was used. The material direction was assigned separately for each finite element, depending on the result of the simulation of the injection moulding process. In the snap model, three parameters have been defined that could potentially affect the simulation results. These parameters have been used for the Design Of Experiments (DOE). By changing the geometric parameters mentioned above, a full set of tests was performed, which resulted in the formation of assembly forces, pulling forces and the maximum stress in the clip, served as input data for optimization. Based on a series of simulations carried out for the material in an As Received (AR) state and after material ageing, geometry optimization was carried out using the Response Surface Method (RSM). Assuming the same requirements during optimization, two different geometries were obtained, for the AR material, and for the material after ageing, which indicates the necessity to carry out similar studies already in product development in order to avoid costly and time consuming changes of serial production tools. The geometry of the latch after optimization, for the material model after ageing, ensures that the requirements for the assembly and the pull out forces needed for part destruction, posed for such components, will be met, while using the optimum geometry for the AR material does not ensure compliance with the requirements after the ageing process. The presented simulation method, taking into account the degradation of the material, enables the optimization of composite structures including the degradation of the material during the operation, which can contribute to significant savings during the design of components made of short fibres reinforced composites and the validation process.