Investigation into the analytical model for predicting the bulletproof performance of composite sandwich structures with UHMWPE laminates under high speed impact of cylindrical projectiles

Objectives This thesis aims to establish a theoretical analysis model on UHMWPE composite sandwich structures against cylindrical projectiles in high speed. Methods By dividing the penetrative process of anti- cylindrical projectile impact of UHMWPE composite sandwich structure into 3 stages and investigating the problem of energy dissipation in each stage, equations between dissipative energy and residual velocities were respectively built in the theoretical analysis model that ignores cylindrical projectile upsetting and considers its influence. The numerical model of resistance to cylindrical projectile of UHMWPE composite sandwich structure was established, the residual velocities of projectile were calculated and the ballistic limits were fitted by using the finite element software ANSYS/AUTODYN. The results of theoretical analysis model and numerical model were compared. Results Based on the results of numerical model, the ballistic limit errors of both theoretical analysis models that neglect and consider upsetting of projectiles are less than 20%. The theoretical analysis model taking projectile upsetting into account has higher calculation precision when the maximum errors, mean errors and correlation coefficients are considered together. Conclusions The theoretical analysis model radicated in this work can be well applied to calculate ballistic limits of UHMWPE composite sandwich structures against the cylindrical projectiles impact and provide a reference for the penetration resistance calculation of other fibre composite sandwich structure. Key words：ultra-high molecular weight polyethylene; composite sandwich structure; ballistic performance; projectile penetration; ballistic limit.