Multimaterial Topology Optimisation of Eco-efficient Fibre-reinforced Composite Structures
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Material selection is one of the core steps in reducing the environmental impact of structures. In general, it is advantageous to use several materials simultaneously, distributing them spatially according to their properties to better deal with multiple conflicting design objectives, such as mechanical performance and environmental impact. Manufacturing approaches such as 3D printing bring freedom of material placement whilst also streamlining the manufacturing of multimaterial parts via automated toolpath generation, especially when using filaments with the same polymer matrix but reinforced with different types of fibre. Here we address the concurrent optimisation of topology and fibre orientation of multimaterial 3D printed composite structures. We present a formulation for minimising their carbon footprint, while balancing stiffness and printability. Regarding manufacturability, the main practical concern is the divergence between the fabricated object and the computational model, which is associated with performance losses introduced during the post-processing of the result. This is implicitly avoided by controlling the numerical instabilities on the material interfaces via the material interpolation scheme and a continuation method, resulting in sharp boundaries that closely match the ones present on the final G-code. Numerical experiments show that our implementation is capable of generating a wide range of material ratios, even structures close to single material, leading to consistent results when applying tighter or looser constraints. The presented formulation can be used as a starting point for the development of other 3D printing-specific considerations, such as explicit self-supportability constraints. By enhancing the optimisation with more steps of the product life cycle assessment, it can be part of a complete framework for the design of eco-efficient composite structures.
