高应力水平下T700/MTM46复合材料层合板拉-拉疲劳性能研究

STUDY ON THE TENSION-TENSION FATIGUE PROPERTIES OF T700/MTM46 COMPOSITE LAMINATES UNDER HIGH STRESS LEVEL

本文研究了T700/MTM46复合材料层合板在高应力水平下的拉-拉疲劳性能。首先开展了层合板静拉伸试验研究,得到了静拉伸强度、模量和破坏应变,各项静力性能指标分散性小,静力破坏模式以小范围内的脆性断裂为主。然后根据得到的静强度确定疲劳应力水平,开展层合板拉-拉疲劳性能试验研究,各应力水平下疲劳寿命分散性大,且并没有随应力水平高低表现出规律性;疲劳破坏模式以分层失效为主,几乎整个工作段长度内都出现了严重的分层现象;疲劳应力水平越高,破坏时刚度下降程度越小,且归一化刚度退化曲线表现出"快-慢-快"三阶段性;疲劳过程中损伤起源于90°层,且在疲劳过程中该层内的损伤扩展最为严重,0°层的损伤出现最晚,但是0°层纤维断裂预示着即将发生灾难性的疲劳破坏。

Tension-tension fatigue properties of T700/MTM46 composite laminates under high stress level were studied in this paper. Static tensile properties were investigated to obtain the ultimate tensile strength, modulus and failure strains. The static index has small scatter and the static failure modes are mainly characterized by the brittle fracture in a small region. Fatigue stress levels were determined by the ultimate tensile strength. Then the tension-tension fatigue tests were conducted. The scatter of fatigue life in each stress level is relatively large, which do not show clear trend with the change of the stress level. Fatigue failure modes of composite laminates are mainly serious delamination through the whole gauge length. The higher the stress level is, the more serious the stiffness decreases. Moreover, the normalized stiffness degradation curves exhibit three obvious stages characterized by "Quick-Slow- Quick" trend. The damages in fatigue loading initiate from 90° plies and show the most serious damage. Damages in 0° plies during fatigue loading appear latest. However, the fiber breakage in 0° plies indicates the coming catastrophic fatigue failure.