Experimental studies on mechanical behavior and microstructural assessment of glass/epoxy composites at low temperatures

A series of flexure tests with varying crosshead speed were conducted to study the mechanical behavior of glass/epoxy composites at low temperature. The micromechanics of damage growth and failures underpin the understanding of the revealed fractography. The three-point flexure test of heat-treated and untreated samples was carried out, which were further exposed to low and ultra-low working temperatures of −20°C, −40°C, −60°C, −80°C. The interlaminar shear strength was found to be affected by these conditionings. The unbalanced and inhomogeneous stress concentration within entangled chain of matrix reduces conformational isomerism which in turn reduces the ILSS value considerably at low crosshead speed. At increased crosshead speed (strain rate), the matrix becomes brittle and fracture strain decreases, but at very high strain rate, the fracture strain increases. The reason is anticipated to be adiabatic heating. Temperature-modulated differential scanning calorimetry shows increase in glass transition temperature (T_g). A change in crosshead speed may result in variation of failure modes, which is observed in scanning electron microscope.