Material transformation
This lesson introduces material transformation modeling, including phase change, ablation, charring, and thermo-optical property degradation, for simulating materials exposed to intense thermal environments.
This lesson may include hands-on exercises. Review the Discussion section for background information or click the button to proceed to the practical section.
Discussion
Material transformation modeling is used to represent thermal processes in which a material changes state or composition when subjected to intense heating.
Phase change materials (PCMs) absorb or release large amounts of energy at a defined temperature through latent heat. During a phase change, the material temperature remains nearly constant until the latent heat is exhausted. The thermal solver supports bidirectional solid–liquid phase change and models the liquid phase as thermally static. Accurate phase change modeling requires appropriate material properties and sufficient mesh resolution normal to the phase change front.
Ablation and charring represent irreversible material transformations caused by intense transient heat loads. Ablation models material removal from the surface, while charring transforms virgin material into a char layer with different thermal properties. These processes are defined using the Ablation-Charring modeling object and are supported for solids, shells, and multi-layer shells. Unlike phase change, ablation and charring are one-way transformations and require implicit time integration.
Material transformation processes are highly sensitive to mesh size and time step size. The thermal solver automatically computes transformation time steps based on latent heat, element mass, and applied heat flux, but careful control of time stepping is often required to balance accuracy and solution time.
In addition to physical material changes, long-term exposure to space environments can degrade surface optical properties. This effect is modeled using Thermo-Optical Properties – State, allowing you to represent changes from beginning-of-life to end-of-life conditions.
Together, these capabilities enable realistic simulation of materials exposed to extreme thermal environments, such as thermal protection systems, phase change storage, and high-heat-flux transient events.
Hands-on material
To gain experience with the topics discussed here, complete the following:
