UHMWPE (Ultra-High Molecular Weight Polyethylene) composites are commonly utilized as a protective material against fragments and projectiles due to the high specific toughness and high longitudinal wave speed of their constituent fibers. They are composed of UHMWPE fibers and a sparse thermoplastic elastomeric matrix, typically Styrene-Isoprene-Styrene (SIS) or Thermoplastic Polyurethane (TPU). UHMWPE composites are inherently difficult to process due to the high viscosity of the thermoplastic matrix and demonstrate a strong sensitivity to processing conditions, particularly consolidation pressure. The ballistic performance of these composites scales with consolidation pressure, but the underlying mechanisms are poorly understood. Furthermore, the majority of experiments on this material are performed at quasi-static strain-rates, even though when used in protective applications, they are loaded at ballistic strain-rates (10^5 – 10^6 /s). To further understand how processing history, microstructure and loading rate effect the deformation and failure mechanisms of these composites, Dyneema® laminates are consolidated at multiple pressures, the microstructure is characterized with micro X-ray Computed Tomography CT (micro CT), and they are tested in uniaxial out-of-plane compression at strain rates ranging from 10^-3 /s – 10^3 /s while simultaneously capturing the deformation history with high speed video. Image analysis is performed on the resulting high-speed video to measure the lateral deformation of the specimen. Combined with the axial deformation history, obtained from the Kolsky bar, we obtain the complete deformation gradient. Using a finite deformation formulation, we calculate volume change as a function of time and relate this to microstructure evolution in the specimen. This technique is used to study the influence and evolution of microstructure on UHMWPE composites loaded at strain-rates up to 3000 /s.