Military and commercial aircraft in operation face the risk of over-temperature incidents such as fires and high-temperature exhaust gas impingement. After an elevated temperature exposure, the composite properties may be significantly compromised even if the damage appears to be minimal based on visual inspection. Continued operation with a potentially damaged component presents the risk of in-service failures leading to the loss of operational capability and life. Without knowing the criticality or distribution of the thermally induced degradation, a repair solution cannot be implemented to restore the damaged component to the required load-bearing capacity. It is desired to have a simulation tool to provide a quick solution for the damage assessment of a large-scale structure exposed to excessive heat. This paper reports Luna Labs USA’s effort in developing models and a simulation tool to predict the residual strength of carbon/epoxy composites exposed to heat. A thermal decomposition kinetic model was developed based on the thermogravimetric data for the composite material. The residual short beam shear (SBS) strength of the composite was measured and related to the mass loss of the samples subjected to isothermal or constant rate heating. Based on these results, a residual strength model was developed to predict the residual SBS strength of the composite exposed to heat. The model has been validated and used to simulate the degradation of carbon/epoxy composites subjected to isothermal or constant rate heating, or the combination of these two heating processes.