Thermal responses modeling

When subjected to a uniformly distributed fire on one side, the heat transfer through the thickness direction of a plate is dominant, as compared to that in the in-plane directions. Three main zones can be defined through the thickness of an FRP laminate during decomposition  

1) A char and gas zone, where most of the resin material has burnt away (T 7 d)- 

3) A virgin material zone that represents the part of the material that remains unchanged (T Tg). 

The load resistance capacity and post-fire performance of the laminate are largely dependent on the size of the virgin zone, which is mainly determined by the temperature profile in the through-thickness direction. Consequently, the problem of describing the temperature change in the experimentally investigated GFRP slabs can be simplified to a one-dimensional problem (in the face sheet thickness direction). 

Models for the effective thermophysical properties - including mass (density), thermal conductivity, and specific heat capacity - have been developed in Chapter 4. Those material property models are implemented into the heat transfer governing equation in the following. 

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The thermal response of a material is largely influenced by the pyrolysis gases and decomposition heat One way to consider these effects is to introduce them into the final governing equations of the thermal response model another possibility is to consider these effects in the effective thermophysical properties. 

Different kinds of boundary conditions can be considered in the thermal response model prescribed temperature or heat flow boundary conditions as expressed in Eq. (6.3) and Eq. (6.4), respectively [25] ... 

A one-dimensional thermal response model was developed to predict the temperature of FRP structural members subjected to fire. Complex boundary conditions can be considered in this model, including prescribed temperature or heat flow, as well as heat convection and/or radiation. The progressive changes of thermophysical properties including decomposition degree, density, thermal conductivity, and specific heat capacity can be obtained in space and time domains using this model. Complex processes such as endothermic decomposition, mass loss, and delatnina-tion effects can be described on the basis of an effective material properties over the whole fire duration. 

The time-to-failure of a structure or its components is an important issue for structural safety considerations in fire. On the basis of the strength degradation models for FRP materials under elevated and high temperatures developed in Chapter 5, the time-to-failure is predicted for GFRP tubes and laminates under both thermal and mechanical loading in compression. Temperature responses were again calculated using the thermal response model presented in Chapter 6. 

The temperature responses were described by the one-dimensional thermal response model in Chapter 6 as the inputs used for mechanical response modeling. 

The temperature of each layer is calculated using the thermal response model (Chapter 6). 

Figure 10-6 Primary Support Structure and RCS Thermal Expansion Comparison 10.2.4.2 Dynamics and Thermal Response Model...

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