Polymers at Cryogenic Temperatures || Mechanical Behavior of Polymer Composites at Cryogenic Temperatures

Content Provider	Semantic Scholar
Author	Kalia Susheel Shaoyun
Copyright Year	2013
Abstract	High strength, stiffness and low weight remain the winning combination that propels composite materials into new arenas, but other properties are equally important. It offers good vibrational damping and low coefficient of thermal expansion (CTE), characteristics that can be engineered for specialized applications. Commercial composites used in large markets such as, automotive components, boats, consumer goods and corrosionresistance industrial parts. Advanced composites, initially developed for the military aerospace marked offer performance superior to that of conventional structural metals and now find applications in satellites, aircraft, sporting goods and in the energy sector in oil and gas exploration and wind turbine construction. Cryogenic applications of polymeric fiber composites are mainly in super conductivity, space technology and handling of liquefied gases. On contrast, heterogeneous nature and anisotropic behaviour of FRP's, a structural designer is faced challenge in predicting the integrity and durability of FRP laminates. Severe environmental exposure affects physical and mechanical properties of polymeric composite materials resulting in an undesirable degradation. Polymer composites soften, creep and distort when heated to high temperature (>100°C) is accompanied by collapse of free volume as the molecular adjustment takes place, that can result in buckling and failure of load-bearing composites structures. Cryogenic fuel tank is the most structural application of FRP at low temperature. Expose to this cryogenic temperature can cause microcracks as well as delamination in the composites due to thermal residual stresses. These microcracks provide a pathway for the ingress of moisture or corrosive chemicals and possible pathway for loss of cryogenic fluids in the tanks. Matrix resins at low temperature are brittle manner and do not allow relaxation of residual stresses or stress concentration to take place. At low temperatures polymers are well below their glass transition temperature and show little visco-elastic behaviour. Molecular motion of segments or side groups is still possible, but 3 the degrees of freedom decrease with decreasing temperature. This motion influences the damping behaviour of the polymers under cyclic mechanical load. If the temperature dependent relaxation time of molecular motion is equal to the time of external deformation, maximum power dissipation occurs. Simultaneously a change in the shear modulus is observed. The goal of this chapter is to extensively study on the in-plane mechanical properties of FRP composites at cryogenic temperature. The composites which have been considered include carbon, glass and Kevlar fiber-reinforced polymers with different resin matrix.
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Language	English
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Content Type	Text
Resource Type	Article