Indian Journal of Engineering & Materials Sciences Vol. 20, August 2013, pp. 299-309 Tensile, compressive and shear properties of unidirectional glass/epoxy composites subjected to mechanical loading and low temperature services Mohammad A Torabizadeh* University of Applied Science and Technology, Mashhad, 91735-613, Iran Received 6 February 2012; accepted 6 February 2013 Composite materials are subjected to low temperatures in service and this has induced the need for a proper knowledge of low temperature behavior of composites. Most of the research in this field is focused on applying different types of loading and laminated configurations. This paper discusses the experimental study on the tensile, compressive and in-plane shear behavior of unidirectional (UD) glass fiber reinforced polymeric composite under static and low temperature loading conditions. Since UD composite is the basic building block of a composite structure and can be used to make general laminates. In order to fully characterize UD laminate, several experimental tests are performed using an environmental test chamber and a universal testing machine. Thermo-mechanical loads are applied to glass/epoxy unidirectional laminates at room temperature (25°C), -20°C and -60°C. The results of the present study indicate that low temperatures have a significant effect on composite failure mode. It is also found that the strength and modulus of UD composites both increased with decreasing the temperature in all cases including tensile, compressive and shear loads. On the other hand, the results show that strain to failure decreased by decreasing the temperature. Keywords: Mechanical characterization, Glass/epoxy composites, Low temperature The desire for lower production costs and higher production rates in high-volume markets such as the aircraft and construction industries, combined with the possibility of fast molding processes, high damage tolerance (especially at sub-zero temperatures) and high chemical and environmental resistance make fiber reinforced composites as very attractive materials. Glass fiber reinforced polymer (GFRP) laminates are candidate materials for the insulation of superconducting magnetic coils in future fusion reactors. The study of composite laminates actually involves many topics, such as manufacturing processes, anisotropic elasticity, micromechanics, and fracture and damage mechanics. Residual thermal stresses develop in these materials when they are exposed to low temperatures (below 0°C). These stresses are the result of a difference in the coefficients of thermal expansions (CTEs) between the reinforcement and the matrix. The non-zero state of residual thermal stresses at cryogenic temperatures is the underlying cause of micro cracking in composites, and the micro-cracks could have an important influence on their performance. To secure the structural integrity of composite structures at low temperatures, understanding of the thermo- mechanical behavior of glass/epoxy laminates at low temperatures is of great importance. Takeda et al. 1 examined the thermo-mechanical behavior of cracked G-11 woven glass/epoxy laminates with temperature-dependent material properties under tension at cryogenic temperatures. They found that residual thermal stresses have no significant effect on Young’s modulus and Poisson’s ratio of G-11 woven laminates. In contrast, the effect of residual thermal stresses on the stress distributions near the crack fronts is more pronounced with decreasing of the temperature. Kim et al. 2 studied the tensile properties of a T700/epoxy composite, which had been cycled with thermo-mechanical loads at low temperatures, using an environmental test chamber. They applied thermo-mechanical tensile cyclic loading (up to 10 cycles) to T700/epoxy unidirectional laminates at room temperature (RT) to -50 °C, RT to -100 °C, and RT to -150 °C (CT), respectively. Results showed that tensile stiffness significantly increased as temperature decreased, while the thermo-mechanical cycling had less influence. Tensile strength, however, decreased as temperature decreased down to Cold temperature (CT), while the decreasing rate of strength was reduced after CT cycling. Kriz 3 analyzed the static behavior —————— *E-mail: [email protected]
Tensile, compressive and shear properties of unidirectional glass/epoxy composites subjected to mechanical loading and low temperature services
Jun 24, 2023
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