Fatigue performance analysis of composite joints based on hole deformation
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摘要: 在复合材料的实际应用中,以装配组件或紧固件失效作为复合材料螺栓连接失效的判定准具有极大的风险性。在分析复合材料疲劳损伤发展特点的基础上,本文提出了一种基于连接孔变形的螺接结构疲劳寿命预测方法,并以碳纤维复合材料双钉单剪及单钉双剪连接拉-拉疲劳性能实验数据对模型进行了验证。结果表明:连接孔的变形量能很好地反映连接结构疲劳损伤的发展过程,本文所提的疲劳寿命预测模型的最大误差不超过−3.62%,装配间隙的存在可导致连接件疲劳寿命下降高达64.8%。Abstract: In the practical application of composite materials, using the failure of assembly components or faste-ners as a criterion for determining the failure of composite bolted joints brings great risks. After analysis of development characteristics of fatigue damage in composite materials, a method for predicting the fatigue life of composite bolted joints was proposed, which was based on the deformation of connection holes, and validated by using experimental data on tensile-tensile fatigue performance of double-bolt single-lap and single-bolt double-lap composite joints. The results show that the deformation of the connection hole can well reflect the development process of fatigue damage of the connection structure, and the maximum relative error of the fatigue life prediction model proposed in this paper does not exceed −3.62%. The existence of assembly gaps can lead to a decrease in the fatigue life of the connection member of up to 64.8%.
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Key words:
- composites /
- bolted joints /
- fatigue life /
- hole deformation /
- assembly gap
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表 1 铺层顺序与单层板厚度
Table 1. Layup sequence and single layer board thickness
Laminate number Stacking sequence Single layer thickness/mm A [±45/0/45/0/−45/−45/90/45/0/±45] 0.15 B [45/90/−45/0/90/0/45/−45/90]s 0.2 表 2 层合板尺寸参数
Table 2. Laminate parameters
Laminate number d/mm L/mm W/mm A 4 140 24 B 6 135 36 Notes:d—Initial aperture; L—Laminate length; W—Laminate width. 表 3 构件完全失效时疲劳实验结果记录
Table 3. Record of fatigue test results when the component fails completely
Number Gap height/mm Gap length/mm q/% s Complete failure-1 0 0 80 88696 Complete failure-2 0.5 12 80 59575 Complete failure-3 1.0 12 80 31221 Complete failure-4 0 0 70 126992 Complete failure-5 0.5 12 70 120713 Complete failure-6 1.0 12 70 121978 Notes:q—Stress level; s—Fatigue life. 表 4 固定循环次数孔变形测量结果记录
Table 4. Record of hole deformation measurement results with fixed number of cycles
Number Gap height/mm Gap length/mm q/% Number of cycle Hole deformation-1 0 0 80 20000 Hole deformation-2 0 0 75 20000 Hole deformation-3 0 0 70 60000 Hole deformation-4 0.5 12 70 20000 Hole deformation-5 1.0 12 70 20000 Hole deformation-6 0 0 65 20000 Hole deformation-7 0 0 60 20000 表 5 孔变形达到0.15d0时疲劳实验结果记录
Table 5. Record of fatigue test results when hole deformation reaches 0.15d0
Number q/% Number of cycle 0.15d0-1 80 38420 0.15d0-2 76 73250 0.15d0-3 72 164401 Note:d0—Initial aperture. 表 6 #1孔和#2孔同应力水平预测模型验证结果
Table 6. Verification results of the same stress level prediction model for holes #1 and #2
Hole number Prediction model Number of cycle Predictive value/mm Actual value/mm Error #1 $ \Delta d=0.00324{n}^{0.45254} $ 60000 0.47 0.49 −3.92% #2 $ \Delta d=0.00320{n}^{0.47593} $ 60000 0.60 0.59 +1.98% Notes: Δd—Hole deformation; n—Number of time of fatigue load. 表 7 #1孔和#2孔同循环次数预测模型验证结果
Table 7. Verification results of the same number of cycles prediction model for holes #1 and #2
Hole number Prediction model Stress level/% Predictive value/mm Actual value/mm Error #1 $ \Delta d=6.61474{q}^{9.05923} $ 80 0.87 0.84 +3.57% #2 $ \Delta d=4.96697{q}^{7.74256} $ 80 0.88 0.89 −1.12% 表 8 3种应力水平下孔变形等应力水平预测模型验证结果
Table 8. Verification results of stress level prediction models for hole deformation under three different stress levels
Stress level/% Prediction model Number of cycle Predictive value/mm Actual value/mm Error 72 $ \Delta d=0.01422{n}^{0.34350} $ 140000 0.833 0.853 −2.36% 76 $ \Delta d=0.03495{n}^{0.27677} $ 100000 0.846 0.854 −0.96% 80 $ \Delta d=0.01778{n}^{0.36831} $ 40000 0.881 0.914 −3.62% 表 9 复合材料螺栓连接结构孔变形预测模型验证对比结果
Table 9. Verification and comparison results of hole deformation prediction models for composite bolted connection structures
Prediction model Number of cycle Predictive value/mm Actual value/mm Error $ \Delta d=4.46\times {10}^{-14}{n}^{3}-2.32\times {10}^{-9}{n}^{2}+5.23\times {10}^{-5}{n}^{}+0.19 $ 400000 1.424 0.914 55.80% $ \Delta d=-0.83318+0.34838{\rm{lg}}_{}n $ 400000 0.770 0.914 −15.75% $ \Delta d=0.01778{n}^{0.36831} $ 400000 0.881 0.914 −3.62% -
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