In-plane shear properties of multi-axial pultruded composites at elevated temperatures
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摘要: 为研究纤维布、剪切面、温度对多轴向拉挤复合材料抗剪性能的影响，对短切毡(剪切面垂直于或平行于纤维方向)增强的传统拉挤复合材料及90°单轴布和±45°/90°三轴布增强的多轴向拉挤复合材料，进行了常温及高温下的面内抗剪试验。结果表明，破坏模式主要为斜对角方向的微屈曲、脱层和剪切失效，并取决于纤维布和剪切面。纤维布对抗剪性能有着重要影响，常温下三轴布增强试件的平均抗剪强度为67.5 MPa，远远好于单轴布及短切毡增强试件(44.4 MPa和45.2 MPa)。剪切面对抗剪性能有一定的影响，常温下剪切面垂直于纤维方向的短切毡增强试件的平均抗剪强度好于平行于纤维方向的强度(38.9 MPa)。然而，随着温度的升高，各组试件的抗剪性能迅速降低，同时各组抗剪性能的差异也逐渐减小。基于热动力学理论和并联定律的单向复合材料抗剪性能计算模型总体上也适用于多轴向拉挤复合材料。最后，在相关试验的基础上提出了适用于高温下多轴向拉挤复合材料抗剪强度、剪切模量的计算公式。研究结果可为高温下的多轴向拉挤复合材料抗剪设计提供依据。Abstract: In order to investigate the influences of fiber-mat, shear plain and temperature on the shearing properties of multi-axial pultruded composite materials, the in-plain shear experiments on the traditional composites strengthened with chopped strand mats (shear plane perpendicular to or parallel to fiber direction), as well as the multi-axial pultruded composites strengthened with 90° uniaxial mat and ±45°/90° triaxial mat, were carried out at elevated temperatures. The results show that the main failure modes are diagonal micro buckling, debonding and shear failure, depending on the mat and shear plain. The shear properties significantly depend on the woven. Under ambient temperature, the average shear strength of specimens strengthened with the triaxial mat is 67.5 MPa, which is significantly greater than those of the specimens strengthened with the uniaxial mat and the chopped strand mat, which are 44.4 MPa and 45.2 MPa, respectively. The shear properties also depend on the shear plain. Under ambient temperature, the average shear strength of the chopped strand mat reinforced specimens with the shear plane perpendicular to the fiber direction is higher than that of the specimens parallel to the fiber direction (38.9 MPa). However, with the increase in temperature, the shear properties for all group specimens reduce rapidly while the difference in each group gradually becomes smaller. The calculation model for shear property of uniaxial pultruded composites based on thermal kinetic theory and parallel law is generally suitable for multi-axial pultruded composites. Finally, a formula was proposed for the calculation of shear strength and shear modulus of multi-axial pultruded composites at elevated temperatures. The research results could provide a basis for the shear design of multi-axial pultruded composites at elevated temperatures.
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图 1 多轴向E6386T级玻璃纤维布
Figure 1. Multi-axial E6386T glass fiber mat
CSM—Chopped strand mat; UM—Uniaxial mat; TM—Triaxial mat
图 3 CSM结构E6386T玻璃单丝/EL-400不饱和聚酯多轴向拉挤复合材料热分析试验结果
Figure 3. Thermal analysis results of CSM structure E6386T glass fiber/EL-400 unsaturated polyester multi-axial pultruded composites
图 4 E6386T玻璃单丝/EL-400不饱和聚酯多轴向拉挤复合材料剪切破坏模式
Figure 4. Shear failure modes of E6386T glass fiber/EL-400 unsaturated polyester multi-axial pultruded composites
图 5 E6386T玻璃单丝/EL-400不饱和聚酯多轴向拉挤复合材料剪应力-剪应变曲线
Figure 5. Shear stress-strain curves of E6386T glass fiber/EL-400 unsaturated polyester multi-axial pultruded composites
图 6 E6386T玻璃单丝/EL-400不饱和聚酯多轴向拉挤复合材料的剪切强度
Figure 6. Shear strength of E6386T glass fiber/EL-400 unsaturated polyester multi-axial pultruded composites
图 7 E6386T玻璃单丝/EL-400不饱和聚酯多轴向拉挤复合材料剪切模量
Figure 7. Shear modulus of E6386T glass fiber/EL-400 unsaturated polyester multi-axial pultruded composites
图 8 不同文献中玻璃纤维/不饱和聚酯复合材料的归一化抗剪强度
Figure 8. Normalized shear strength of glass fiber/unsaturated polyester composites from different literatures
图 9 玻璃纤维/不饱和聚酯复合材料的归一化试验值与公式计算值
Figure 9. Normalized experimental and calculated values of glass fiber/unsaturated polyester composites
EXP—Experience point; CAL—Formula calculated value
表 1 试验工况
Table 1. Test configurations
ID Reinforced fabric Number of layers Density/(kg·m−3) Shear plane Target temperature/℃ NT CSM 3 1893 Perpendicular to the fiber 20, 40, 60, 80, 100, 120, 140, 180 NP CSM 3 1893 Parallel to the fiber 20, 40, 60, 80, 100, 120, 140, 180 UT UM 3 1836 Perpendicular to the fiber 20, 40, 60, 80, 100, 120, 140, 180 TT TM 3 1928 Perpendicular to the fiber 20, 40, 60, 80, 100, 120, 140, 180 Notes: In specimen ID, the first letter: N—Chopped strand mat; U—Uniaxial mat; T—Triaxial mat; the second letter: T—Perpendicular to the fiber; P—Parallel to the fiber. 
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表 2 E6386T玻璃单丝/EL-400不饱和聚酯多轴向拉挤复合材料剪切强度、模量预测模型输入值
Table 2. Input parameters for prediction of shear properties of E6386T glass fiber/EL-400 unsaturated polyester multi-axial pultruded composites
Strength retention rate Modulus retention rate τg/τg τl/τg τd/τg Gg/Gg Gl/Gg Gd/Gg 1.00 0.09 0.01 1.00 0.08 0.01 Notes: τ—Shear strength; G—Shear modulus; Subscripts g, l and d—Glassy state, viscous state and decomposition state, respectively.
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