Design and simulation of an innovative cylinder fabricated by selective laser melting

Additive Manufacturing(AM) processing has attracted wide attention due to its advantages, e.g., rapid prototyping and free design. In aeronautic and astronautic engineering, it is especially attractive to apply AM processing, especially Selective Laser Melting(SLM), into primary structures that always occupy most of the whole mass of aircraft or spacecraft. In this paper, an innovative lattice sandwich structure that is suitable to be manufactured with SLM is adopted to design the typical cylinder under axial compression. Firstly, the mechanical properties of pyramidal lattice are investigated, and the bearing capacity of the lattice sandwich cylinder is given analytically for each failure mode. Secondly, a composite cylinder is re-designed in the form of lattice sandwich structure, which sizes are ultimately obtained through optimization. Finally, finite element model of the innovative cylinder is established and several kinds of imperfection are introduced to simulate the defects caused by SLM. Numerical result shows that the lattice sandwich design can obviously enhance the bearing capacity of cylindrical shell even though the original one is designed with composite material. In other words, SLM has great potential in improving the primary structure of spacecraft in the future.

Failure modes of lattice sandwich plate by additive-manufacturing and its imperfection sensitivity

Additive-manufacturing process has substantially promoted the development of lattice structure and makes it possible to fabricate complex lattice sandwich structures.In-plane compression load always appears in engineering,such as in the primary structure of spacecraft.In order to reveal potential engineering application in future,this paper focuses on the lattice sandwich plate that is fabricated by additive-manufacturing and subjected to in-plane compression.Firstly,five failure modes are proposed for lattice sandwich plate under in-plane compression,including Euler buckling,shear buckling,face sheet dimpling,face sheet wrinkling and face sheet crushing.Secondly,an optimization method is proposed to obtain the optimum sizes,including the panel thickness,the length of rod,the size of rod cross-section,the inclined angle of rod and the wideness ratio of cell.Then,the in-plane compression experiment is operated after measuring the geometrical imperfection of the specimen by the optical microscope.Numerical method is adopted to illustrate the effect on failure behaviors caused by the imperfections of struts,face sheets and global shape.By introducing these imperfection,numerical result can be well agreed with experimental result and explain the failure mechanisms mostly derived from the radius imperfection for the struts.