Design and optimization method for 3D printed carbon reinforced aircraft components

Recent developments in the field of plastic additive manufacturing have seen the introduction of carbon fibres in printed products. These fibres improve the strength and stiffness of the thermoplastic based components. Two approaches are currently seen, the very short fibre embedded in the printing filament and continuous fibres, where the focus for this research is on the latter. The improvements observed to strength and stiffness from adding continuous fibres are very interesting and could be used to optimize parts and reduce weight, which is important for aerospace applications, see Figure 1. However the design approaches currently use trial and error to determine the fibre content in the parts. A design and analyses method is proposed to predict the mechanical behaviour of the material and the printed components with parameters such as fibre type, geometry and filling. The novel method proposed for the continuous fibre reinforced 3D printed design uses the finite element approach. The thermoplastic and the fibre are meshed independently and are combined using numerical algorithms. From the independent meshes the local element stiffness response is calculated and the stress, strain and deformation of the components can be predicted. The approach is very flexible; the fibre mesh can be adjusted independently so that the local reinforcement design can be changed and optimized. The mechanical properties of the fibres, thermoplastic material and layer adhesion are calibrated using test data on coupon level. (Figure Presented) The proposed method can further be used to predict manufacturing induced effects which are mainly related to temperature changes. Thermoplastic material tends to shrink when cooled down, which combined with the layered approach in 3D printing causes large residual stresses. These stresses may cause distortion of the component or even failure during the printing process. The proposed method is capable to predict these thermal effects. With the presented approach, 3D printing with continuous carbon fibres is moving from the current trial and error approach to right first time designs. This enables further optimization of the component design and process parameters, achieving weight reduction. The application of this technology in aerospace non-critical components, if more mature, is foreseen for interior parts such as hinges or seat frames.