thesis

Fire structural properties of sandwich composites

Abstract

The main aim of this PhD project is to investigate the fire structural properties of a sandwich composite representative of the material used in naval ship structures. Using experimental techniques and analytical models, this PhD investigates the structural response of sandwich composites during and following fire exposure. The thermal, physical and mechanical processes controlling the softening and failure of the sandwich composite under structural loading and one-sided heating by fire are determined. Two important structural loading cases of axial tension and axial compression are studied together with different radiant heat flux conditions representative of fires with different flame temperatures. To thoroughly understand the fire response of sandwich composites, this PhD determines the temperature response, softening behaviour, deformation, damage and failure mechanisms for different loading conditions, stress levels and heat flux conditions. In post-fire structural properties, reductions to the tensile and compressive properties of sandwich composites following fire exposure are investigated experimentally and analytically. The processes and mechanisms controlling the post-fire stiffness and strength properties of sandwich composites are determined. This PhD project also assesses the effect of water absorption on the fire structural response of sandwich composites. The sandwich composite was exposed to a hot-wet environment for increasing periods of time to controllably alter the amount of absorbed water. The effect of absorbed water on the thermal and mechanical responses of the sandwich composite in fire is experimentally determined. The research determines changes to the thermal response, damage, softening rate and failure mode of the sandwich material with increasing concentration of absorbed water up to and above saturation. This PhD research work establishes a better understanding of mechanical performance and failure mechanisms of sandwich composite structures at high temperature and in fire. In addition, the research identifies the thermal, physical and mechanical processes that control the structural survivability of sandwich composites during and following fire exposure. The research provides the foundation for the development of design models and guidelines for sandwich composite structures for high fire risk applications, thus improving fire safety for ships, offshore platforms, civil infrastructures and other uses for these materials

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