Preparation And Mechanical Properties Of SiC/SiC Ceramic Lattice Core Composite Sandwich Structures

Lattice core sandwich structure has broad application in aerospace field due to its light weight,high strength and excellent performance.The conventional lattice core sandwich structures are made of metal or resin-based composite materials,which cannot be used in high-temperature conditions.Thus,it is urgent to develop ceramic-based lattice core composite structures that can satisfy the need of high temperature service.In this work,the preparation process and mechanical properties of SiC/SiC lattice core composite sandwich structures are studied.The main research contents and results are as follows:The method of preparing SiC/SiC ceramic composites by SLS-forming technology and PIP post-treatment process was studied.The effects of laser sintering parameters,such as laser power scanning rate,layer thickness and filling pitch on the accuracy and density of the green parts,were analyzed.The laser sintering parameters were optimized by the orthogonal tests.The experimental results show that the scanning speed and filling pitch have great influence on the strength of SLS-forming SiC/SiC composites while the layer thickness and laser power have obvious influence on the dimensional accuracy of the composites.Based on the results of this analysis,the optimal parameters of SLS-forming technology were proposed and used to fabricate SiC/SiC composites combined with PIP post-treatment.The compression properties,failure mechanisms and failure modes of SLSformed SiC/SiC lattice core composite sandwich structures with three different configurations(the inclination angles are 45°,50° and 60°,respectively)under room temperature and high temperature conditions(1400 ℃,1600 ℃,1800 ℃)were investigated experimentally.It is found that the values of elastic modulus and compressive strength of the SiC/SiC lattice core composite sandwich structures with 60° inclination angle at room temperature are the largest,which are 1.20 GPa and 55.32 MPa respectively.The SiC/SiC lattice core composite sandwich structures with 45° inclination angle have the lowest elastic modulus and compressive strength,which are 0.55 GPa and 20.86 MPa,respectively.Under the temperature of 1400 ℃ and 1600 ℃,SiC/SiC lattice core composite sandwich structures retain high compression strength as well as 30 MPa.However,the compressive strength of SiC/SiC lattice core composite sandwich structures at 1800 ℃ decreases by 7 MPa.A numerical simulation model of SiC/SiC ceramic lattice core composite sandwich structures was established.The mechanical responses of SiC/SiC ceramic lattice core composite structures were studied.The stress field distribution,equivalent compressive modulus and strength were obtained.The compression failure mode and failure mechanisms were analyzed.The failure modes of the SiC/SiC ceramic lattice core composite structures predicted by the simulation in this work agree with the experiment results.At the same time,the effects of the pores in the SiC/SiC ceramic lattice core composite sandwich structures on the stress field and equivalent elastic modulus were investigated.