Numerical Modelling of the Rate-sensitive Behaviour of High-performance Fabrics
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RESEARCH PAPER
Numerical Modelling of the Rate‑sensitive Behaviour of High‑performance Fabrics D. Weerasinghe1 · D. Mohotti2 · J. Anderson3 Received: 25 February 2020 / Accepted: 19 September 2020 © Society for Experimental Mechanics, Inc 2020
Abstract Fabric-based soft armour is the most commonly employed means of personal protection under conditions where ballistic threats are prevalent. The fabric types most commonly used in soft armour are p-Aramids and Ultra High Molecular Weight Polyethylene (UHMWPE). Extensive research, both numerical and experimental, has been carried out to improve and optimise the performance of such materials. Numerical modelling has proven to be a useful tool in capturing the kinetics of highly dynamic events such as ballistic impact. However, the rate-sensitive properties of materials such as p-Aramids and UHMWPEs remain largely unaddressed in numerical models. Furthermore, approximating failure with element deletion based on critical stress levels is unable to account for the progressive damage that yarns undergo during an impact. This paper aims to propose a rate-sensitive constitutive model (RSCM) including rate-sensitive stress–strain response, failure and progressive damage for such materials. A hybrid modelling approach is also presented where different element formulations were used while retaining computational efficiency. The RSCM was implemented as a user-defined material subroutine in LS-DYNA. The results of numerical simulations are in close agreement with experimental results. Hence, the RSCM presented in this paper can be used to accurately model the response of high-performance Twaron fabrics made from p-Aramids subjected to ballistic impact. Keywords User-defined materials · Constitutive model · Impact · Rate-sensitive · High strain rate · Twaron fabric · p-aramids
Introduction The aim of this paper is to develop a constitutive model which captures rate-sensitive features of high-performance Twaron fabrics that is easy to implement and is computationally efficient. Ballistic impact events generate strain rates in the range of 102–104. Even though it has been established that the stress–strain behaviour of fibres such as p-Aramids (Kevlar and Twaron) is rate-dependant [1, 2], most numerical * D. Weerasinghe [email protected] 1
School of Civil Engineering, Faculty of Engineering, The University of Sydney, Camperdown, NSW 2006, Australia
2
School of Engineering and Information Technology, The University of New South Wales, Canberra, ACT 2600, Australia
3
Presidium Systems Pty Ltd, Payneham South, SA 5070, Australia
studies still employ rate-independent elastic constitutive models [3–8]. Consequently, the viscoelastic properties of such fabrics are not captured in the modelling. Therefore, there is a need for a constitutive model that includes ratesensitive behaviour of fabrics with viscoelastic properties. The current state-of-the-art in simulating ballistic impact on woven fabrics use orthotropic elastic constitutive models [9]. Ge
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