Generative design for additive manufacturing of polymeric auxetic materials produced by fused filament fabrication

The durability improvement of mechanical systems produced by Additive Manufacturing has become a key challenge in the industry, especially with architectured materials which present enhanced physical properties. Additive Manufacturing has also made it possible to develop architectured materials which are cellular or distributed materials in which the topological allocation is controlled and optimized for specific functions or properties, such as auxetic materials. Auxetics are structures that have a negative Poisson’s ratio which becomes thicker perpendicular to the applied tensile force. Moreover, Generative Design is a design exploration process to create highly optimized design making additive technology one of the best ways to access some new design space. This work aims to combine Generative Design and Integrated Design as part of a simultaneous approach to evaluate the capabilities of auxetic materials made by Fused Filament Fabrication in 3D printing. Three main aspects are considered in this approach: the parametric design of a pattern geometry to generate a structured part considering fabrication constraints through design guidelines, the additive manufacturing of the generated part and the evaluation of the structured material’s mechanical behavior. Three-point bending tests are also carried out to validate the analytical approach as well as to study auxetic structures properties. This parametric design methodology allowed for the fabrication of auxetic bending specimens. Outcomes from mechanical tests were used to elaborate an equivalent simplified beam model to predict the elastic behavior of auxetic materials before manufacturing. Then, the mechanical tests have shown also that the pattern’s compression around stress application aims to reinforce the structure. The results show the potential of the implemented global and simultaneous approach to develop auxetic materials through a Generative Design for Additive Manufacturing methodology. Hence, this research work provides a basis for further work to improve the numerical analysis aspect and extend the approach to develop architectured and functionalized materials. The results show multiple auxetic design iterations of bending specimens based on geometric, material, and additive technology parameters in order to verify their mechanical behaviors.