Cryogenic failure mechanisms of fiber‐epoxy composites for energy applications

Abstract

Fiber‐reinforced composites used in the production, storage, and transport of energy are often exposed to extreme environments such as cryogenic temperatures and/or nuclear radiation. The fraction resistance of composites subjected to these conditions are of fundamental interest. A study was undertaken to examine the effects of Gammaradiation on the structure and properties of fibers, matrix and their interfacial bonding in terms of their influence on composite failure mechanisms. Also thermomechanical analysis was conducted to estimate the residual thermal stresses due to differential thermal expansion coefficients both between fiber and matrix and between two laminae. Results indicate that the impact energy of a composite laminate could be increased by 100 percent by immersing the specimen in liquid nitrogen for only five min. Samples impact‐tested at cryogenic temperatures were found to possess a great degree of delamination and crack bifurcation. Thermomechanical analysis and SEM investigation both reveal that microcracking and small‐scale delamination are promoted by differential thermal contraction. Such effects could be responsible for the observed crack branching and delamination phenomena during impact loading. Although under certain circumstances the Gammaradiation may yield a small increase in fracture resistance it generally degrades the cohesive strength of the matrix and reduces the interfacial bonding between fiber and matrix. Results of a mechanical and microscopic analysis are presented and discussed.

Experimental study on the mechanical behavior and microstructural assessment of Kevlar/epoxy composites at liquid nitrogen temperature

“…The impact energy level and temperature were found to have significant effects on the impact behavior of fiberglass and the combinations of fiberglass with Kevlar [17]. However, the fracture behavior and mechanism of the laminate composites at low and high temperature levels are complicated when compared with those of the composite at room temperature [18][19][20][21]. In the present investigation, an attempt has been made to study the mechanical behavior of Kevlar epoxy composites at LN 2 temperature and to correlate the failure modes, which are responsible for the degradation of composite materials.…”

Effect of Cryogenic Cycles on Mechanical Behavior of Glass/Epoxy Composite

“…As the laminate temperature falls below its stress-free temperature, residual stresses develop in the material. These stresses are the result of the large difference in the linear coefficient of thermal expansion (CTE) between the fibers and the matrix 6,7 . As the temperature of the material deviates more from the stress-free temperature, the amount of thermal stress in the material increases.…”

The role of temperature on impact properties of Kevlar/fiberglass composite laminates

“…Thus, low and high heat resistance of composites has to be given serious consideration. However, the fracture behavior and mechanism of the laminate composites at low and high temperature levels are complicated when compared with those of the composite at room temperature [7][8][9][10][11][12][13][14][15].…”