Measurement of strain in fabrics under ballistic impact using embedded nichrome wires, part II: Results and analysis

A new technique using nickel–chromium wire, called the NiCr (Nichrome®) wire technique, has been presented in a first paper describing the technique [1]. This second paper focuses on the results obtained when this new technique is applied to ballistic fabrics. Strain distributions on the layer impacted, as well as in different layers, are presented. An energy balance based on the strains is shown to provide reasonable values for the elastic energy stored by the yarns. Failure times of the first layer as a function of impact velocity are discussed and a simple momentum balance is shown to predict well the deflection history of the fabric. Ultra-high-speed photography and high-speed videos allowed recording of fabric deflection vs. time. The combination of the four diagnostic techniques, including X-rays, delivers a very complete picture of the impact mechanics in fabrics, both for early-time and late-time phenomena.