Appearance of new polymer formulations, every time with higher thermal stability, has lead industry to consider polymeric composites for high temperature applications, where is important to know the behavior of such materials under the effect of fire, mainly for safety reasons.In this work a polyimide composite will be characterized via TGA-DSC and DMA techniques, in order to obtain the necessary parameters to use as an input for modeling the fire behavior. The approach to accomplish so is divided in two parts, one the thermal model which will be the responsible for providing the thermal response (temperature and weight loss distributions) and which is based on the COMFIRE software, and the mechanical model which will provide the evolution of the laminate stiffness matrix during the time of exposure and will be based on the classical laminate theory.A two step decomposition process of the polyimide was observed, characterized by being exothermic, obtaining a maximum weight loss of 35%wt. And results from the simulation showed small losses of stiffness with small effect of degradation, that took place once the glass transition temperature (Tg) had been reached. Also the fact that symmetric laminates became asymmetric due to the effect of the temperature gradient through the thickness of the composite, although it recovered its symmetry if the Tg was reached and there was a low amount of decomposition.