Modelling the effect of temperature on the probabilistic stress–life fatigue diagram of glass fibre–polymer composites loaded in tension along the fibre direction

Abstract

Predicting the fatigue performance of composites has proven to be a challenge both conceptually, due to the inherent complexity of the phenomenon, and practically, because of the resource-intensive process of fatigue testing. Moreover, mechanical behaviour of polymer matrix composites exhibits a complicated temperature dependence, making the prediction of fatigue performance under different temperatures even more complex and resource intensive. The objective of this paper is to provide a method for the prediction of fatigue life of glass-polymer composites loaded in the fibre direction at various temperatures with minimal experimental efforts. This is achieved by using a static strength degradation approach to fatigue modelling, where only two parameters (including static strength) are temperature dependent, in conjunction with relationships for these two fatigue model parameters temperature dependence. The method relies on fatigue data at a single temperature and simple static tests at different temperatures to predict the effects of temperature on the material's fatigue behaviour. The model is validated on experimental data for two unidirectional (UD) and one woven glass-epoxy composites and is found to accurately predict the effect of temperature on fatigue life of composites. A method to obtain probabilistic stress-life (P − S − N) fatigue diagrams including temperature effects is also discussed. 1

Modelling of Environmental Ageing of Polymers and Polymer Composites—Durability Prediction Methods

“…These are comprehensively discussed and systematised in numerous review papers [ 121 , 126 , 129 , 130 , 131 , 132 , 133 , 134 ]. The traditional models are often used in conjunction with statistical data analysis [ 135 , 136 , 137 , 138 , 139 ]. The present section is not aimed to give an in-depth discussion of the fatigue models but point out the main differences in existing modelling approaches that are crucial for fatigue prediction under environmental impact.…”

“…Different forms of this function are considered in numerous research studies and reviews [ 121 , 125 , 126 , 136 , 140 , 146 , 147 , 148 ]. Failure occurs when the residual strength equals the maximum cyclic stress.…”

“…However, these are not widely accepted within the engineering community due to the extremely high experimental cost of measuring the residual strength (due to a large number of destructive tests, material- and testing-related sensitivity, etc.) [ 136 ]. Nevertheless, the strength degradation approach is advantageous in many cases due to the ability to account for the effect of fatigue damage without the need for its detailed analysis cycle-by-cycle.…”

“…Although these approaches can contribute to understanding the damage mechanisms under the environmental impact, these are characterised by limited versatility since all the fitting parameters are specific for a given material only. Modelling of fatigue properties by this methodology has been used by Tang et al [ 151 ], Khan [ 152 ], Cormier et al [ 136 ], Mivehchi et al [ 149 ], Koshima et al [ 167 ], Eftekhari and Fatemi [ 78 ], Amjadi and Fatemi [ 166 ], Prabhakar et al [ 145 ], Solfiti et al [ 168 ], and Acosta et al [ 169 ]. The results are summarised in Table 2 regarding the environmental factors, material and testing parameters, and general concepts employed in modelling.…”