Protection technologies, security, situational awareness
The absorption of cw and long-pulse laser radiation in solids leads to a strong and fast temperature raise due to the beam absorption. The propagation of the thermal process can be mathematically described by the heat conduction equation. For special cases with simple geometries an analytical solution can be found. For more general cases only numerical calculations can be achieved.
This PhD project aims to focus on the mathematical modelling of complex and multiphasic issues of laser – composite structures and materials interaction, including chemical degradation processes. It is a complementary effort of the ongoing thesis of Vadim Allheily with a stronger emphasis on the solver implementation.
The numerical modelling is performed by the so called Finite El-ement Method (FEM). Solving the partial differential equations requires a multiphysics package solvers. Beside commercial solu-tions, the free and open-source multiphysical simulation software ELMER could be a potential alternative. ELMER includes physical models of fluid dynamics, structural mechanics, electromagnetics, heat transfer and acoustics, for example. Thanks to its modular structure, own module can be further implemented. Starting from modules included in the ELMER package and modules written at ISL for laser impact and material removal in homogenous materi-als, new modules have to be developed to respect the heterogene-ous structure of composite materials. Besides direct laser heating also combustion due to chemical reaction at elevated temperature acts as an important additional heat source and has to be included in the modelling.
The project is broken-down into the following steps:
- Literature survey of laser – composite interaction modelling
- Modelling of the beam absorption, including the consequences of the matrix ablation and pyrolysis
- Implementation of the models within ELMER suite
- Simulations calibrations with complementary experimental measurements.
At least calculations performed for different laser and material parameters should be compared with experimental results.