Microscopic Simulation Study on Uniaxial Compressive Creep Characteristics of Coal Samples Constrained by Different Numbers of Carbon Fiber Reinforced Polymer Strips
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摘要: 为探究不同数量碳纤维增强复合材料(carbon fiber reinforced polymer, CFRP)条带对轴压煤样蠕变力学特性的影响,耦合PFC3D软件与FLAC3D软件,结合伯格斯(Burger’s)模型与平行黏结(Linearpbond)模型,建立混合接触的细观数值模型。根据未约束煤与6条带CFRP约束煤样单轴压缩蠕变室内试验,验证了数值模型的可靠性。研究了2~7条带CFRP约束煤样在单轴压缩蠕变下的力学特性及能量演化。研究表明:随着条带数的增加,煤样在初始阶段的轴向应变整体呈现增大趋势,加速蠕变阶段轴向应变明显增大;混合接触模型内部接触的最大力整体呈现增大趋势;伯格斯模型接触数量与平行黏结模型接触数量的比值约为1∶9时,数值模拟模型能够反映出煤样蠕变的力学特性;增加CFRP条带数,煤样的径向变形受到限制,产生的剪切微裂纹增多,煤样内部的剪切破坏更加严重,煤样的破坏形态由张拉破坏逐渐向剪切破坏转变;随着碳纤维布条带数量的增加,煤样的总能量、弹性能、耗散能均增加,在煤样发生蠕变失稳前,弹性能的变化与总能量的变化较为相似。
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关键词:
- 碳纤维增强复合材料 /
- 条带数 /
- 单轴压缩蠕变 /
- 伯格斯模型 /
- PFC3D-FLAC3D耦合
Abstract: To investigate the influence of carbon fiber reinforced polymer (CFRP) strip with different number on the creep mechanical properties of coal samples under axial compression, a coupled numerical simulation using PFC3D and FLAC3D software was conducted, and a hybrid contact model combining the Burger’s model and the Linearpbond model was established. The reliability of the numerical model was validated based on laboratory uniaxial compressive creep tests of unconstrained coal and coal samples constrained with 6 strips of CFRP sheet. The mechanical properties and energy evolution of coal samples constrained with 2 to 7 strips of CFRP sheet under uniaxial compression were studied by numerical simulations. The results show that as the number of strips increases, the initial axial strain of the coal sample tends to increase overall, with a significant increase in axial strain during the accelerated creep stage, and the maximum internal contact force in the hybrid contact model tends to increase overall. The ratio of the contact quantity of Burger’s model to that of Linearpbond model is about 1∶9, and this ratio in the numerical simulation model could reflect the creep mechanical properties of coal samples. Increasing the number of CFRP strips restricts radial deformation, increases the number of shear micro-cracks, causes more severe shear damage within the coal sample, and the failure mode of the coal sample changes from tensile failure to shear failure. As the number of strips increases, the total energy, elastic energy, and dissipated energy all increase, and the change in elastic energy is similar to the change in total energy before the coal sample experiencing creep instability. -
表 1 接触模型的细观参数
Table 1. Microscopic parameters of contact model
Linearpbond model Linearpbond effective modulus/GPa Linearpbond
stiffness ratioNormal bond strength/MPa Tangential bond strength/MPa Coefficient of friction Angle of friction/(°) 1 1.4 10 10 1.5 50 Burger’s model Maxwell bulk modulus/MPa Maxwell viscosity coefficient/(MPa·s) Kelvin bulk modulus/MPa Kelvin viscosity coefficient/(MPa·s) Coefficient of
friction1 90 10 1 1.5 表 2 CFRP条带模型参数
Table 2. Model parameters of CFRP sheets
Tg/MPa Eg/GPa t/(mm·ply−1) φi/(°) 918.07 47.54 0.167 30 表 3 不同数量CFRP条带约束煤样破坏时的力链
Table 3. Force chains in coal samples at failure constrained by different numbers of CFRP strip
Number of strips Number of contacts Maximum contact force/N 2 30511 434.7 3 28852 534.9 4 29378 678.2 5 28609 570.7 6 25655 979.5 7 25747 1121.7 表 4 不同数量CFRP条带约束煤样破坏时的裂隙数量
Table 4. Number of cracks in the failure of coal samples constrained by different numbers of CFRP strip
Nunber of strips Number of tension cracks Number of shear cracks Total number of cracks 2 1420 7 1427 3 3014 287 3301 4 2167 389 2556 5 2553 1107 3660 6 6832 2457 9289 7 4295 5012 9307 -
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