Structural battery composites are multifunctional materials capable of storing electrochemical energy while providing mechanical reinforcement. The multifunctionality is enabled by carbon fibres, which serve as both structural load reinforcement and electrodes due to their graphite-like microstructure. Chaudhary et al. demonstrated state-of-the-art structural battery composites by embedding carbon fibre electrodes in a bi-phasic structural electrolyte, a so-called Structural Battery Electrolyte (SBE), consisting of a solid phase for load transfer and a liquid phase for ionic transport. As lithium inserts in the electrode, the carbon fibres expand in an anisotropic sense causing internal stresses in the SBE. Previous models by Larsson et al. overestimate these stresses, largely due to a simplified neo-Hookean material model and a lack of experimental data. Recent compression tests on the SBE have shown significant rate-dependent mechanical responses and liquid drainage, with fluid seepage increasing at lower strain rates as shown in Figure 1. In this work, we aim to model the experiment using a 1D axisymmetric finite element representation to simulate the SBE’s mechanical behaviour and fluid seepage under compression. The model couples quasi-static equilibrium and Darcy-type-seepage in finite deformation setting, incorporating fluid pore pressure to capture stress-assisted fluid transport