The combination of random and controllable--- design strategy and mechanical properties of directional random porous structures inspired by Wolff's law

Porous structures have received extensive attention due to their excellent mechanical properties. Inspired by Wolff's law, a new design method for directional random porous structures (DRPS) that is based on principal stress lines is proposed. Considering three working conditions, namely, cantilever bending, shearing and compression, the mechanical properties and deformation modes of a directional random porous structure in the loading direction were studied via numerical simulation. The results show that the directional random porous structure significantly reduces both the maximum stress and deformation, as well as the stress concentration within the model. The design model was prepared via a light curing process with the photosensitive resin R4000 as the raw material, and its deformation pattern and mechanical behaviour under local and overall compression conditions were investigated. During local compression loading, the selection of different principal stress lines affects the mechanical properties of the structure. Selecting a dense area of principal stress lines with a large transfer stress as the directional growth design area can result in better strengthening efficiency. The experimental results under overall compressive loading conditions show that the design method proposed in this paper can substantially improve the mechanical properties of the structure in the strengthening direction while ensuring the mechanical properties in the non-strengthening direction, in which the modulus of elasticity, ultimate compressive strength and specific energy absorption (SEA) were improved by up to approximately 140.97%, 58.59 % and 51.32 %, respectively.