HyTop: Development of a coupled topology optimization method for injection-molded, short fiber-reinforced polymer-metal hybrid composites to support the product engineer in design synthesis

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The aim of this research project is the development of a topology optimization method for the optimization of short-fiber reinforced thermoplastic (SFT) -metal hybrid structures under consideration of thermally induced shrinkage, resulting residual stresses and local anisotropic material properties from the injection molding process. Since the maximum force in the event of failure is decisive for the design of the hybrid structure, it should be maximized in the optimization. As could be shown in previous studies, the shape of the metal insert is decisive for the force-displacement behavior of the polymer-metal hybrid composite for a given polymer matrix and assumed adhesion behavior. Therefore, the topology optimization method to be investigated should optimize the geometry of the metal insert and consider the following aspects: 1) the resulting geometry of the insert and 2) the filling of the resulting cavities in the insert with the SFT-component iteratively. Furthermore, the topology optimization method should consider the material properties of the metal as well as the SFT-matrix in the iterations. For this purpose, models described in the literature for simulating the thermal and mechanical behavior are to be integrated. In addition to the load-dependent strains and stresses, residual stresses in the SFT structure should also be taken into account. Representing the two materials of the considered hybrid structure, the steel insert is modelled according to the material HC420LA and the surrounding SFT matrix according to the thermoplastic polypropylene with variable glass fiber reinforcement content of 20, 40 and 60 volume-%.The following subgoals can be derived for the development of the topology optimization method for the design of SFT-metal hybrid structures:• Investigation of suitable modelling approaches for the simulative mapping of the mechanical and thermal properties of the SFT-matrix in the structural model for topology optimization• Investigation of different modeling approaches of the cohesive zone between metal insert and SFT-matrix in the topology optimization method• Investigate a method for automatically building the structural model for topology optimization, including filling the gaps in the metal insert with the complementary material• Investigation of different approaches for the adaptation of the sensitivity-based topology optimization process for the optimization of the SFT-metal hybrid structures in shape finding• Derivation of design guidlines and implementation of corresponding boundary conditions into the topology optimization method (e.g. minimum radii, minimum cavity size)