Research On Experiment And Design Of Composite Fragile Cover Made Of Multiple Parts

The missile launcher canister cover is very important part in the missile launch systems. The cover can protect the missile by keeping the pressure of inert gas in the launcher canister, and destroyed by the high speed airflow when the missile launching. The traditional missile launcher canister cover has been replaced by composite fragile cover, because of they are heavy, complex, and slow to response. In this paper, composite fragile cover made of multiple parts is proposed to solve the problem of composite fragile cover made of whole part that the separated part mass is large. The structure of composite fragile cover made of multiple parts is designed and the mechanical properties are calculated.The first part in the paper, according to the use conditions and destroy requirements, the multiple parts composite fragile cover is mainly divided into three parts that respectively named separated part, weak area, framework, and the separated part are made of four unit cover by adhesive bonding. Three preliminary structures schemes of multiple parts composite fragile cover are proposed, and the deformation and stress are compared by numerical calculation. The deformation and stress of flat-plate fragile cover are maximum one of the three types, so the flat-plate is suitable for multiple parts fragile cover. The round-cap type cover and the spherical type cover are more suitable than flat-plate type. The structure design and laminate composite of two types are made, and the double-side lap adhesive bonding joint is used for the weak area structure type by compare different adhesive bonding joint specially.The second part, studying on the destroy type and the strength of weak area structure. The micro structure of weak area is established, the strength of weak area structure is determined by numerical simulation under eleven different ratios of bending-stretching coupling load, and the strength envelopes were developed subsequently. According to maximum principle stress rule, the curves of strength and structure parameters versus different bending-stretching coupling load were presented and parametric design method of the weak structure was proposed. The crack fracture toughness of I type and II type are observed by experiment of DCB and ENF. The maximum stress rule is used to determine the direction of crack development, and the B-K rule is used to calculate the energy release rate. Lastly the crack development is simulated by XFEM method, and the effect of structure parameters and load are discussed.The third part, the deformation and stress are presented by numerical finite element analysis. The gas flow is numerical simulated by CFD in missile launcher canister, the results show the inner surface pressure of cover will raise to 0.3MPa in 3ms. The deformation and stress of round-cap type cover and the spherical type cover are calculated by numerical finite element analysis on 0.02 MPa, 0.3MPa,-0.03 MPa. The mechanical properties of deformation and stress of spherical type are better than round-cap type. Then the mechanical properties of 1/4 model of finite element are calculated under three working conditions, and the strength of weak area structure and glue layer are checked.The last part, the multiple parts composite fragile cover of two type are made to back pressure experiment and air-sealing experiment, the result show the air-sealing properties of two structure types are well. The rush experiment result show the spherical type cover is better to suit multiple parts composite fragile cover than round-cap type. The errors of design are discussed.