As their name suggests, 3D-textile reinforced composites are manufactured by intertangling yarns together in three-dimensional space to create a near-net-shape dry fabric preform. After infusing this preform with a resin matrix system, a lightweight component is created which demonstrates both high in- and out-of-plane stiffness and strength. The through-thickness reinforcements present in this class of materials, prevent delamination and allow for stable and progressive damage growth in a quasi-ductile manner. Despite their advantageous mechanical properties, the complex yarn structure creates a material with a number of interesting behaviours and features which need to be accounted for when developing a model to predict how the material will deform and eventually fail. To begin with, these materials are highly anisotropic and show varying levels of non-linearity depending on loading mode. This non-linearity can be due to a variety of subscale behaviours: microcracking in the matrix or fibre-bundles, yarns straightening and fibres breaking as well as viscous effects from the polymer matrix. These materials, in particular in shear and off-axis loading modes, have been shown to have behaviour which is dominated by the viscous effects of the polymer matrix [2] even at relatively low loading rates. Using the knowledge gained from a previous experimental testing campaign [2], this works develops and presents a phenomenologically based macroscale model to predict how the material deforms under mechanical loading. It considers the material as a homogenous and anisotropic solid and predicts the development of damage, plastic and viscous behaviours. The model is applied to a notional aeroengine component and in particular demonstrates the importance that additional off-axis yarn reinforcement will play in future applications.