The reliability of marine evacuation systems is of paramount importance for the personal safety of crew members. This paper aims to improve the reliability of marine evacuation systems by proposing a constitutive model for TPU composite membranes and a deformation prediction model for inflatable beams. The constitutive model for the TPU membrane is based on the continuum theory of mechanics. Its effectiveness is validated through a series of off-axis angle stretching tests, and the model’s predictions fit well with the data, with errors within 10%. This model exhibits high efficiency and accuracy compared to micro-scale models. The deformation prediction of the inflatable members is based on the Le Van inflatable beam model, considering multiple influencing factors. The effectiveness of this model is verified through a comparison with bending and axial loading experiments, demonstrating its ability to better describe the shear effects of inflatable members during the bending process compared to the Le Van model. The research presented in this paper provides a systematic and reliable theoretical model for composite material inflatable members.