Civil Engineering - Theses
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ItemDevelopment of fabric-reinforced polyurea structures for ballistic protection( 2016)Textile-reinforced structures have been increasingly applied in personal protective armours due to their blast and impact resisting capabilities. Their enhancement in energy absorption, lightweight, flexibility, and fragments capturing capabilities when subjected to ballistic impact made them the preferable alternative options to traditional metallic materials. However, the recently developed multi-laminate structures with rate-dependent and non-homogeneous materials have substantially increased the complexity in analysing the behaviour of such systems, which renders the traditional experimental-reliant development approach less capable. This research aims at establishing a new development approach for multi-material laminate structures using finite-element modelling, supported by the experimental testing of basic material properties and structural performance. A new polymer-textile laminate structure was investigated by constructing virtual composite laminate models using LS-DYNA® package. Using the third-party software commanded via the custom-developed python code, the ballistic model of the meso-scale single layer Kevlar® 29 woven fabrics was first constructed and validated to study the evolution of kinetic, strain, and frictional energy components of the fabric during the ballistic impact, as well as its damage mechanism. An improved meso-scale solid element model was then developed to resemble the Twaron® fabric properties, in order to study the influence of the woven structures and projectile impact resistance. The results have shown superior performance from the plain weave structure in comparing to other architectures. To simulate the multi-layer fabric structures, further studies using various mesh sizes have led to the development of a hybrid-mesh finite element model, which simulates the inter-yarn and inter-layer contacts of the multi-layer fabrics with enhanced computational efficiency of over 500%. The numerical models of the textile-reinforced polyurea structures were eventually constructed by combining the meso-scale hybrid-mesh Twaron® fabric model with the nonlinear polyurea model. Ballistic impact on the three-section layup structures consist of polyurea sheets and fabric piles of similar areal density was then simulated. Comparison between various multi-material structures provided insights into the criticality of the material layup arrangements. Energy absorption mechanism was compared among all structural arrangements to reveal the contribution and energy absorption capacity (EAC) of each structure.