Research on the microcrack behavior of carbon fiber/epoxy composites under prestress and ultra-low temperature cycling
The use of composite materials in low-temperature fuel tanks is an effective approach to achieve weight reduction and enhance carrying capacity for launch vehicle structures.However,as the tank is subjected to both ultra-low temperature cycling and mechanical loads during service,it is prone to internal microcrack formation in composite materials,posing a threat to structural safety.In this study,a simple pre-stressing device was used to conduct ultra-low temperature cycling tests on carbon fiber/epoxy orthotropic laminates.The research focused on the initiation and evolution of microcracks in composite laminates under the combined action of pre-stress and ultra-low temperature cycling.The results indicate that the microcrack density at the edge layers of the laminate is generally higher than that in the inner layers,but the central two 90° stacked layers exhibits the maximum micro-crack density.Compared with conditions of only low-temperature cycling,the pre-stress results in a higher micro-crack density in the laminate under the same number of low-temperature cycles,with a faster growth rate.With an increase in the number of cycles,the growth rate of microcrack density initially accelerates and then slows down,eventually reaching saturation.As the pre-stress level increases,the initiation and propagation rates of microcracks in the laminate are further intensified.This study provides a preliminary insight into the mechanism of microcrack initiation and evolution in composite materials under the coupled action of load and ultra-low temperature cycling,offering meaningful references for the development and application of low-temperature composite material tanks.
carbon fiber/epoxy compositeslaminatesultra-low temperature cyclingpre-stressmicrocrack
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