Research On Dynamic Mechanical Response And Ballistic Performance Of High-strength And High-modulus Polyimide Fiber

With the continuous development of bulletproof equipment,fiberreinforced resin composites are widely used in the field of individual combat due to their high strength,high toughness,and light weight.Polyimide fiber is a kind of high-performance fiber emerging in recent years.It has outstanding mechanical properties,such as resistance to high and low temperature,UV resistance,environmental resistance,etc.Its protective material can withstand high-speed ballistic impact;can be used normally in extreme battlefield environment,showing a good application prospect in the field of bulletproof.The mechanism of the bullet penetrating the composite target is relatively complicated,and the dynamic mechanics research of the composite under high strain rate is the focus of the current research field.In this paper,the dynamic mechanical response and ballistic performance of PI fibers are studied.The tensile performance and compression performance of PI fiber under high strain rate were studied through dynamic mechanical test,and the fracture failure mechanism was analyzed through macro and micro morphology;the ballistic limit velocity V50 of PI fiber composite target was tested based on ballistic test.The impact of resin content,resin type,reinforcement structure,bullet type,fiber type,etc.on the ballistic performance is analyzed.The penetration mechanism of the bullet and the energy absorption mechanism of the target plate are analyzed through the macro and micro morphology of the target plate and bullet hole.Research indicates:(1)During high-speed stretching,the fracture stress and modulus of PI fibers increase,while the fracture strain decreases.When PI fiber breaks under quasi-static conditions,plastic flow will occur at the fracture;at high strain rates,the axial splitting of the fiber is intensified,the fibrillation phenomenon is obvious,and a lot of microfibers burst out.The weibull strength distribution model of the fiber tow shows that when the fiber is stretched at a high speed,the probability of breaking at the weak point decreases and the breaking stress increases,which is consistent with the experimental results.It provides a theoretical basis for the application of PI fiber in bulletproof.(2)During high-speed compression,the compressive strength and elongation at break of polyimide fiber reinforced composite are increased;the compressive strength of carbon fiber reinforced composite is lower than that of quasi-static,and the elongation at break increases.The compressive strength of the hybrid fiber reinforced composite(HFRP)is between the two,and it increases with the increase of the strain rate.Through reasonable structural design,HFRP can exhibit excellent toughness characteristics while maintaining a certain strength under high-speed compression.(3)In the ballistic test,when the resin content of the composite is less than 20%,it is beneficial to improve the ballistic performance of the laminate.The ballistic performance of the UD structure is better than that of the fabric structure.The ballistic performance of the thermoplastic resin system is better than that of the thermosetting resin.UD structure has better anti core bullet effect and fabric structure has better anti fragment effect.The destruction methods of the front and back surfaces are shear failure and tensile failure respectively.The PI fiber target plate has excellent ballistic performance and has great potential applications in the field of bulletproof.