Armor Protection Performance Of Metal-Intermetallic Laminate（MIL） Composites Ti/Al₃Ti

Metal-Intermetallic Laminate（MIL）composites Ti/Al₃Ti is widely applied in the field of armor protection due to its high modulus,high specific strength,low density and high hardness.Therefor it is very important to study its damage modes at high and ultra-high velocities.However,there are a few investigations assoacted with this novel armour material,which are carried out by experiment that can not reveal the complex damage modes of Ti/Al₃Ti under high and ultra-high velocities effectively.Mature simulation technology provides an effective solution for the high and ultra-high velocities penetration.SPH coupled with FEM method simulates the high velocity penetration well.In the large deformation area,the SPH method is used for avoiding the grid distortion in order to ensure the calculation accuracy.The FEM method is used in the small deformation area to ensure the calculation accuracy and computational effectiveness.SPH method is used for simulating the Aluminum ball penetrating target in ultra-high velocity which belongs to large deformation problem.It can ensure the accuracy of calculation.So,SPH-FEM method and SPH method were employed in this work.Metal-Intermetallic Al₃Ti,Metal-Intermetallic Laminate（MIL）composites Ti/Al₃Ti and SiC fiber reinforced Metal-Intermetallic Laminate（MIL）composites Ti/Al₃Ti were fabricated by ZRT-60-30 vacuum hot-pressing furnace using SiC fiber,Al foil and Ti foil as raw materials in this thesis.The density of the material was tested by using archimedes method.The elastic modulus and Poisson’s ratio were tested by ultrasonic method.The static and dynamic compressive strength and failure strain of the material were measured by INSTRON5500R and SHPB.Based on the above experiments,the JH-2 constitutive model of Al₃Ti and Ti/Al₃Ti can be calculated via curve fitting which provides a basis of simulation.In order to further understand the failure modes of Ti/Al₃Ti,SPH-FEM method was employed to simulate the process of tungsten alloy bullet penetrating Ti/Al₃Ti layered composite target.Damage and failure modes in different moments of Ti/Al₃Ti can be obtained in this process.The results indicated that Ti layers on target produce a petal-shaped crack,accompanied by different level peeling.Besides,Al₃Ti layers appear radial groove-like damage and circumferential cracks,accompanied by shedding phenomenon.The special layered structures of Ti/Al₃Ti enable that the direction of crack propagation changes continuously,which results in the deflection of the cracks and the increase of crack propagation paths.Therefore,Ti/Al₃Ti absorbs more impact energy and exhibit superior ballistic performance.In addition,SPH method was employed to simulate the impact of the aluminum alloy ball penetrating the fiber-reinforced layered composite Ti/Al₃Ti target with different volume fraction of SiC fibers of 0,1%,2%,5%and 10%at penetration speed of 2000 m/s and 4000m/s,respectively.The relationship between the protective properties and the speed and the fiber content of SiC fiber reinforced Ti/Al₃Ti layered composite target were investigated.The simulation results indicated that the damage of the target is much more serious than the velocity of 2000 m/s when the bullet velocity is 4000 m/s.When the velocity is the same,the energy absorbing effect of SiC fiber reinforced Ti/Al₃Ti layered composite is the best when the content of SiC fiber is 2%.This provides a direction for the study of the relationship between the protective properties of SiC fiber reinforced Ti/Al₃Ti layered composite target and the speed and fiber content.