Optimal fibre architecture of soft-matrix ballistic laminates

• A new methodology is proposed for characterisation of lay-ups.
• Local failure is shown to be related to inter-ply angle.
• Global failure is shown to be related to anisotropy of lay-up.
• Pull-out is demonstrated to have a first order effect on penetration velocity.

Soft-matrix ballistic laminates (such as those composed of fibres of Ultra High Molecular-Weight Polyethylene, e.g. Dyneema® HB26 and Spectra Shield) find extensive use as catching type armour systems. The relationship between the lay-up of these laminates with respect to the observed failure mechanisms has not been empirically investigated in the open literature, and is the subject of this work. Lay-ups are characterised by two parameters: (i) sequencing (or interply lay-up angle) θ¯ and (ii) in-plane anisotropy ββ, and can be mapped on to θ¯–ββ space. Four geometries that lie at the extrema of this parameter space are designed, built and tested. Testing is through ball bearing impact on circular clamped plates. The anisotropy (ββ) is coupled to the macroscopic response of the plates, while sequencing (θ¯) is coupled to the microscopic response. Penetration velocity is strongly affected by pull-out at the boundary, and in the present study this is shown to account for two-thirds of the ballistic resistance. The results have implications for validation testing on scaled samples, predictive modelling and simulation, and armour design.

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