Modeling Assumptions and Simplification

When exposed to high temperatures and fire, FRP composites experience complex changes in material states involving the interaction of thermal, chemical, physical, mechanical, and structural phenomena. Modeling and predicting aU the coupled responses of FRP stmctures is therefore a complex task. By treating independently only one or two of these phenomena in each model, however, the task becomes more reasonable. The thermal phenomena (heat transfer, temperature distribution, etc.) are mainly determined by the thermophysical properties of the material and the thermal boundary conditions, while the mechanical and stmctural phenomena 

Complex reactions are involved in the changes of material state of FRP materials under elevated and high temperature. For simplification, it is convenient to describe this process in four stages [24]  

1) Heating Energy is transferred to the material up to (decomposition temperature of resin). 

2) Decomposition The chemical bonds of the polymer are progressively broken and decomposition products are formed (residual char, various liquids, smoke, incombustible and combustible gases). 

3) Ignition Ignition occurs when a sufficient concentration and proper form of the fuel source mixes with an oxidizing agent at the proper temperature. 

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