Speaker
Description
Composite materials, due to their high strength to weight ratio, are deployed in various aerospace applications such as skins of the empennages (aircraft), launch vehicle bodies, support structures in spacecraft, etc. However, the cryogenic tanks for storing super cooled fuels such as liquid nitrogen (LN2), liquid oxygen (LOX), liquid hydrogen (LH2), etc. in spacecraft are still constructed by means of metals. Even with years of testing, still the concern exists about the leakage of tanks at cryogenic temperatures due to the microcracking of composite laminates such as carbon/epoxy. These microcracks arise owing to difference in the coefficients of thermal expansion in axial as well as transverse directions. The composites exposed to very low temperatures (cryogenic temperatures) causes thermo-mechanical loading even at moderate pressure, due to which the crack propagates that leads to the formation of leakage paths. These leakage paths allow the fuels to leak that cause the ignition and explosion hazard. However, in order to overcome such catastrophic incidences, Kevlar®, a Para-aramid synthetic fibre, proves a promising alternative to be used for cryogenic storage tanks. Kevlar® composite had proved to be a highly suitable material for applications ranging from sports equipment and body armour to spacecraft. In the present work, the failure behaviour of Kevlar®/Epoxy laminate (60% fibre volume fraction) under uniaxial tensile load ranging from 100MPa to 1000MPa is determined by using the extended finite element method (XFEM) approach. A three-dimensional Kevlar®/Epoxy laminate of 50x30x1mm with a 5mm edge crack at the mid position of the laminate is considered for analysis. Further,stress-strain characteristics of Kevlar composite are compared with those of normal metals (SS316LN) used for cryogenic storage tank applications.