Development of Lightweight Soft Body Armour for Ballistic Protectio

Strong and low-density fibres have been favoured materials for ballistic protection, but the choice of fibres is limited for making body armour that is both protective and lightweight. In addition to developments of improved fibres, alternative approaches are required for creating more protective and lighter body armour. This research focuses on a study of the inter-yarn friction and hybrid fabric panels for ballistic protection. Two complemetary routes have been employed to carry out the research, namely a programme of experimentation centred on ballistic shooting test and a detailed theoretical analysis based on finite element (FE) modelling. In this research, fabrics made of ultra-high-molecular-weight polyethylene (UHMWPE) were chosen for investigation due to their good mechanical properties and light weight. For the investigation of inter-yarn friction on fabric ballistic performance, FE models were created in ABAQUS software for theoretical analysis. According to the capstan equation, yarn wrapping angle is one of the factors controlling inter-yarn friction. This being so, novel weaving techniques have been developed to manufacture woven fabrics with increased yarn wrapping angle. Ballistic shooting tests have been carried out on the structure modified woven fabrics and the results showed that the improvement of ballistic peotection on structure modified fabrics is not detectable when compared with plain woven fabric. This could be attributed to the low inter-yarn coefficient of friction of UHMWPE fibres and low increase in wrapping angle due to the high bending rigidity of UHMWPE fibres. Based on the two points, improvements have been suggested for future work.For the development of hybrid panels, an eight-layer woven fabric FE model was created to study the response and failure model of different fabric layers in a panel upon ballistic impact. It has been established that fabrics near the impact face tend to fail by the shearing effect and those near the back face tend to fail in tension. UHMWPE woven and unidirectional (UD) fabrics were evaluated for their resistence to tensile and shearing damage. Two types of panels were designed from the fabrics and the experimental results showed that placing woven fabrics close to the impact face and UD material as the rear layers led to better ballistic performance than the panel constructed in the reverse sequence. It has also been found that the optimum ratio of woven to UD materials in the hybrid ballistic panel was 1:3. The improvement in ballistic protection of the hybrid fabric panels allows less material to be used, leading to lighter weight body armour.