This contribution presents an approach for the simultaneous topology optimization of an isotropic (e.g. metallic) part, the layup optimization of a composite part, and the search for the optimized position of the joints between the two parts. For that, the approach presented in [1] is extended by the optimization of composite parts. The joints are modelled by spring elements, where the loads of their reference points are distributed over a circular pattern. The degrees of freedom of these patterns are coupled to the connected parts through the shape functions of the parts’ elements. For the topology optimization, the pattern is considered as non-design space by projecting the joint pattern on the density field. The design variables considered in this optimization are the (pseudo) densities of the isotropic parts, the fiber orientations in each element and ply of the composite parts, as well as the positions of the reference points of the joint nodes. Since a gradient-based optimization algorithm is employed, the gradients of objective and constraint functions are derived with respect to all design parameters. The results show that an individual optimization of one part may be critical for the performance of the connected part and hence, worsens the overall performance. The proposed simultaneous optimization approach however allows to efficiently improve the performance of the assembly of parts. REFERENCES [1] O. Ambrozkiewicz and B. Kriegesmann, „Simultaneous topology and fastener layout optimization of assemblies considering joint failure“, International Journal for Numerical Methods in Engineering, 122 (1), 294–319, 2021, doi: https://doi.org/10.1002/nme.6538.