MODELING OF THE THERMOPHYSICAL AND THERMOMECHANICAL PROPERTIES OF FIBRE REINFORCED POLYMER (FRP) COMPOSITES UNDER ELEVATED TEMPERATURES

Summary

As the range of applications for fibre-reinforced polymer (FRP) composite materials in material engineering
constantly increases, there is more and more concern with regard to their performance in critical environments.
The behavior of composite materials in high temperature environments is especially important since complex
physical and chemical processes such as the glass transition and decomposition occur when these materials are
subjected to elevated and high temperatures possibly leading to considerable loss of stiffness and strength. The
stiffness and strength degradation in composite materials under elevated temperatures is the result of changes in
polymer molecular structures. When polyester thermosets are subjected to elevated and high temperatures they
undergo three transitions (glass transition, leather to rubbery transition and rubbery-to-decomposed transition)
corresponding to four different states (glass, rubbery, leathery and decomposed). At elevated temperatures a
composite material can therefore be considered a mixture of materials that are in different states. As the content
of each state varies with temperature the polymer composite exhibit temperature dependent properties and this
forms the basis for the development of property sub-models for composites at elevated temperatures. The result
show that the elastic modulus, E reduces with increase in temperature fig 1: the thermal conductivity, K also
decreases with increase in reciprocal temperature fig 2.

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