Master thesis and internship[BR]- Master's thesis : Thermo-mechanical modeling of composite materials subjected to fire[BR]- Integration Internship

Abstract

Composite materials, and especially Polymer Matrix Composites, are increasingly used in engineering applications such as in aerospace or marine structures. The environments in which they are used can be prone to fire events. However, the fire resistance of Polymer Matrix Composites is rather poor. This is explained by the fact that the polymer matrix reacts to fire and undergoes pyrolysis. Premature failures are therefore occurring. It is thus important to be able to model the thermo-mechanical response of composites subjected to fire in order to prevent these failures. This type of modeling, including pyrolysis, is not available nowadays at some companies working on composite materials. It is therefore useful to investigate this subject. In this work, the physics related to composites in fire are first explained. The most used thermo-mechanical models are identified. A common feature between them is the use of a two-step analysis. First, a thermal analysis is performed. It is then followed by a decoupled mechanical analysis. This work is focusing mostly on the thermal part. A thermal model developed by Henderson et al. is found to be a reference in that domain. The classical mechanical models are also briefly explained. Using the finite element software Samcef, the thermal model is solved. The detailed methodology required to use correctly the software is given. Some adaptations of the formulas and the material properties are done. A methodology used to perform a short mechanical analysis is also given. The results from the thermal model, and more specifically the temperature distributions, are compared to experimental and analytical results found in the literature. They are not very conclusive in the first instance. The value of the matrix decomposition energy must be increased in order to improve the results. It is also shown that some properties must be tuned to fit the experimental curves when the material data is not precisely known. Eventually, a short and simple mechanical analysis using elastic and advanced material laws is performed and some results are interpreted. It is nonetheless limited by the lack of knowledge about both the thermal and mechanical properties for a same composite material. Therefore, only generic results are obtained. They cannot be over-interpreted.