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Description
Composite helmets are made from a combination of durable synthetic fibers, such as Kevlar (aramid) and ultra-high molecular weight polyethylene, bonded with resins. Composite helmet manufacturing involves layering successive layers in a mold, then heating and subjecting them to hydraulic pressure, creating an integral, robust helmet shell. Structural damage to the helmet can occur both during production and during use. To extend its service life, the entire batch of helmets should be evaluated. Only non-destructive testing allows for the examination of an entire batch of helmets and the identification of those with internal structural damage that reduces their ballistic resistance. Due to the shape of the helmet shell, ultrasonic thermography is the most effective method for detecting defects. To verify whether the type of defects detected using ultrasonic thermography significantly reduces the helmet's ballistic resistance, we use the V50 destructive testing method. The V50 method in ballistics is a standard procedure for testing the ballistic resistance of materials. It involves determining the velocity at which, on average, 50% of projectiles penetrate the material and 50% stop (or partially penetrate), thus defining the material's protective limit in accordance with military standards. This article presents selected results of non-destructive testing of composite helmets after many years of use and their verification using the V50 destructive method.
