Spacecraft are under constant threat of structural damage from hypervelocity impacts by micrometeoroids and orbital debris. To bolster the shielding used for protection against these impacts, ballistic materials can be employed. Aramid-based materials are currently used aboard the International Space Station (ISS), but Ultra High Molecular Weight PolyEthylene (UHMWPE) fibres are a common alternative for ballistic protection on Earth. In this report, the suitability of UHMWPE-based composites for spacecraft impact shielding is investigated. Hypervelocity impact simulations using smoothed particle hydrodynamics discretisation form an essential part of the design and analysis of such protection systems. Two formulations of nonlinear orthotropic hydrocode models are proposed for this purpose, which are validated using footage from hypervelocity impact experiments on Dyneema® HB26 targets. One of the proposed models yields good prediction of residual impactor velocities, generally being within 10% of experimental data. The other reproduces both residual velocities and debris cloud shape well for the highest considered impact velocities, but suffers from decreased performance as the ballistic limit is approached. Numerical comparison between UHMWPE- and aramid-based composites shows comparable ballistic performance for the considered cases.