Research On Rapid Prototyping SiC Ceramic Matrix Composites And Their Properties

Outer packaging protection material(ceramic material)of aircraft radome must be high temperature resistance,ablation resistance,erosion resistance,thermal shock resistance,and having excellent mechanical strength and so on under harsh conditions.However,ceramic materials have many problems such as strong brittleness,complex fabrication process and high cost.In order to solve the problems above,this paper proposes a low cost rapid prototyping method to prepare carbon fiber(Cw)reinforced silicon carbide(SiC)ceramic matrix composite.The concrete contents are as follows:To improve ceramic precursor yield and curing performance,organic precursor of SiC ceramic matrix composites(propargyl polysilazane,PPSZ)is prepared by deacidification condensation of polysilazane(LSZ)and bromopropyne under the condition of alkaline acid binding agent.The results show that the ceramic yield of PPSZ resin after sintering at 900? is about 81%?83%.However,the amount of precursor required to prepare the ceramic matrix composite is large,and the yield of PPSZ resin is low,so it can not meet the demand of experiment.But LSZ resin has the advantages of low curing temperature,good rheological property and high yield.Therefore,LSZ resin can be used to replace PPSZ resin as the ceramic precursor.Short carbon fiber felt(Cw)reinforced LSZ-SiC ceramic based composite material is prepared by preimpregnation molding method.On the basis,the mechanical property and high temperature oxidation resistance of composite materials with thickness less than 1 mm and about 3 mm are investigated,respectively.Firstly,the optimization of preparation processconducted.As a result,the obtained optimal preparation parameters are pressure of 10 MPa,Cw.slurry weight ratio of 1:10,SiC:LSZ:HDI weight ratio of 1:1:0.2,and natural gel.However,the tensile strength of the samples prepared under the above conditions is still stable after high temperature treatment.From the complete structure and good interface bonding between matrix and fiber from the samples after oxidation sintering,we can know that the composites have good environmental durability.Then,Cw reinforced LSZ-SiC ceramic based thick plate composite samples are prepared at pressure of 2 MPa and under unchanged remaining process parameters.The results show that the bending strength of the samples is still stable after high temperature treatment.The research on the the fracture morphology of samples indicates that fiber greatly exerts its toughening performance when composite breaks and thereby ensures the required mechanical strength for the composite material used in high temperature environments.In order to prepare ceramic matrix composites at lower sintering temperatures(<500?)and reduce process cost,aluminum dihydrogen phosphate precursor is adopted to replace polysilazane.Cw-reinforced AlPO4-SiC ceramic matrix composite is prepared by rapid molding technology.The optimal preparation parameters can be summarized as following:SiC:Al(H2PO4)3:H2O:HP:HMTA weight ratio of 3:1:3:0.24:0.12,pressure of 5 MPa,and Cw:slurry weight ratio of 1:10.The bending strength of the resulting composite samples is 87.04 MPa,81.04 MPa and 99.58 MPa,respectively,after the processing of 300?,500? and 800?.Stable mechanical strength indicates that the fiber can carry a large load-bearing effect when the composite material breaks.The composite material has a complete structure and a low loss rate of sintering quality(about 3%to 13%)in an oxygen atmosphere,which suggests its excellent high temperature oxidation resistance.In this paper,a rapid prototyping technology for obtaining high temperature resistant,high toughness resistant and high strength SiC ceramic matrix composites,which greatly shortens the preparation cycle of composite materials.