Abstract
The present study intends to investigate the effect of temperature on cumulative fatigue damage of laminated fibre-reinforced polymer (FRP) composites. The effect of temperature on fatigue damage is formulated based on a previously proposed residual stiffness fatigue damage model. The fatigue strength of FRP composite laminates is also formulated to have temperature dependent parameters. The research work is divided into three main parts; the first part reviews the fatigue damage mechanism is fibre-reinforced composites based on stiffness degradation. The recent residual stiffness of Varvani-Shirazi was used as the backbone structure of damage analysis in this thesis. This model is capable of damage assessment while the effects of maximum stress, stress ratio and fibre orientation of FRP composites were recognized. The Varvani-Shirazi damage model was further developed to assess fatigue damage of FRP composites at various temperatures (T). Inputs of the damage model are temperature dependent parameters including Young's modulus (E), ultimate tensile strength(ðult) and fatigue life (Nf). As the next part of the proposed analysis, the temperature dependency of each parameter is formulated, and the relations of E-T and ðult-T are substituted in the Varvani-Shirazi fatigue model. Finally, all terms and equations are evaluated with the experimental data available in the literature. Six sets fatigue data were used in this thesis to evaluate fatigue of FRP specimens. The predicted results were found to be in good agreement with the experimentally obtained data. The proposed fatigue damage model was found promising to predict the fatigue damage of unidirectional (UD) and women FRP composites at different temperatures. Temperature dependant parameters of Young's modulus, ultimate tensile strength, and S-N diagram were also found to be responsive when used of UD, cross-ply, and quasi-isotropic FRP laminates.
Highlights
Introduction and Application of fibre-reinforced polymer (FRP) Composites1.1 IntroductionComposite materials or composites are formed by combining two or more materials that have quite different mechanical properties
Experimental data extracted from the literature [28,29,33,34] have been used to evaluate the formulations proposed for the ultimate tensile strength and Young's modulus
A cutting machine with diamond blade and water cooling was used to cut the laminates into L = 240 mm, W = 25.4 mm, and t = 2 mm coupons, according to ASTM D3039-93
Summary
Composite materials or composites are formed by combining two or more materials that have quite different mechanical properties. The materials or constituents do not dissolve or blend into each other and maintain their separate (at least microscopic) identities in the composite, but they give the composite unique properties and characteristics that are different from those of the constituents. There are two categories of constituents: matrix and reinforcement. The matrix has a continuous state, and the reinforcement exists in two forms of fibres or particulates. The reinforcements are surrounded by the matrix material [1]. Changing the volume fraction of the reinforcements in the matrix and changing their orientation and arrangement in it, allow designers to produce wide varieties of composites with different mechanical properties
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