Additive manufacturing of bone-inspired structural-power composites

Abstract

Design for additive manufacturing today – benefitting from unprecedented geometrical freedom – isincreasingly exploiting means of structural optimization, including topology optimization, latticing andby taking inspiration from nature. This paper constitutes a case study, highlighting the added value andpotential of combining these structural design approaches in AM, particularly in terms ofmultifunctionality. A method to obtain bone-inspired structural-power composites, designed for fibre-reinforced additive manufacturing, with both high stiffness-to-weight ratio and ionic conductivity ispresented. For this purpose, a sandwich structure with reinforced shell (compact bone) and lattice core(spongy bone) filled with ionic liquid (bone marrow) is proposed. A finite element analysis andcalculations based on a resistance network model provided insight into the change and trade-off betweenmechanical and electrical performance with increasing shell thickness i.e. level of reinforcement.Investigations into fibre angle assignments following the central difference scheme and the medial axistransformation have shown comparable performance, providing ways of controlling and tailoringdeposition paths to best meet requirements associated with the manufacturing with short and continuousfibre-reinforcements. The model with continuous fibre-reinforcement has shown great potential forimproving the specific stiffness compared to the isotropic functional counterpart used as benchmark,while additionally providing the potential for energy storage, constituting a promising theoreticalapproach as to how AM can serve as means for lightweighting through functional integration. It wasconcluded, that in pursuit of improving the efficient material usage, tailored shell-infill designs shouldbe considered in the future.