NUMERICAL SIMULATION OF LOW VELOCITY AND BALLISTIC IMPACT ON POLYMER COMPOSITE LAMINATED STRUCTURES

Abstract

Fiber reinforced plastic materials are widely used in automobile, aviation and defence applications due to their higher strength to weight ratio compared to metal structures. Damage analysis of such structures while subjected to impact is one of the important issues of current research. Typical types of damage are mainly caused during production, repair, maintenance and during in-service collisions. Low velocity impact is considered potentially dangerous mainly because the damage might be left undetected. This type of damage is commonly called as `Barely Visible Impact Damage (BVID)'. One of the typical applications of composite material is that they can be used to provide effective protection for ballistic impact. The present study is carried out for numerical simulation of low velocity impact on thin composite laminated structures with reinforced glass and carbon fibers, as well as for ballistic impact on thick composite laminated structures reinforced with Kevlar fiber. Numerical modeling was developed and used to obtain an estimate for the limit perforation velocity (Ballistic limit velocity, V50) and simulate the failure modes and damage. Computations were carried out using a numerical code based on finite element provided by AUTODYN-3D software, the results of the simulation were analyzed. The study reveals that more curved spherical surfaces offer highest degree of resistance to ballistic impact. Another significant finding of the present investigation is that all layers with same fiber orientation offers best resistance to impact. The study also represents a review of impacts theories as applied to study of damage in composite materials. The present study further includes the simulations on ballistic test standards for KEVLAR and KEVLAR-Ceramic helmets. They are the namely NIJ-STD-0101.03, 0101.04 Level IV. For the simulation on USPASGT-helmet, a NATO 5.56X45 mm standard projectile was considered. The helmet was impacted at an impact velocity of 550-900 m/s. The simulation revealed that impact velocity above 620 m/s is requited to perforate the KEVLAR helmet. The present work can be used for improvement in the design of helmet by application of more spherical surfaces, and by application of ceramic/composite layers, where ceramic is the top layer of the helmet. This helmet design defeats the 900 m/s velocity of NATO-5.56X 45 projectiles. iv