Response Spectrum Optimisation for Lightweight Structures Under Impact
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Carbon fibre reinforced polymers (CFRPs) enable lightweight, high-performance, sparse designs. The sparsity of these composite structures amplifies their complex behaviour, creating a challenging mechanical response landscape. We present a model for an additively manufactured, wound CFRP truss structure composed of connection points ("anchors") and one-dimensional members ("strings"). Anchors are attached to an external surface undergoing assumed deformation. Given the high stiffness contrast, anchors are treated as rigid volumes connected by one-dimensional strings. For the material model of the strings, we rely on a geometrically nonlinear (finite deformation), bimodular elastic formulation. The analytical description results in a continuous formulation of the strain energy, derived by Tangential Differential Calculus (TDC) [1-2]. Ensuring elastic response about a residual stress state is relevant for the design of structures under non-proportional and uncertain loading conditions. Optimising for complementary residual stress states and maximal load factors, results in generally constrained optimisation problems. We present shape optimisation approaches for resilient response spectrum designed CFRP-truss structures subject to impact loads. We formulate an optimal control problem, stated in terms of residual stresses, and optimisation of the response spectrum. The efficient implementation and algorithm design are addressed, based on an adjoint formulation [3]. The proposed approach is demonstrated on real-world engineering case studies, illustrating its effectiveness and computational efficiency in practical applications. [1] A. Sky, J.S. Hale, A. Zilian, S.P.A. Bordas, P. Neff, Intrinsic mixed-dimensional beam-shell-solid couplings in linear Cosserat continua via tangential differential calculus, Computer Methods in Applied Mechanics and Engineering, Vol. 432, 2024. [2] A. Zilian, M. Habera, Nonlinear analysis of thin-walled structures based on tangential differential calculus with FEniCSx, FEniCS conference, 2022. [3] P.T. Kühner, M. Habera, A. Zilian, Sequential quadratic and convex optimisation with FEniCSx and PETSc, KLAIM conference, 2025.
