碳纤维布层数对煤圆柱力学特性影响的细观研究

Mesoscopic study on the effect of CFRP layers on the mechanical properties of coal circular-columns

为探究碳纤维布(CFRP)层数对煤圆柱力学特性的影响。利用三维的FLAC-PFC耦合方法,建立CFRP被动约束煤圆柱的连续-非连续耦合模型,基于已有0~2层CFRP被动约束煤圆柱试验数据验证了细观模型的有效性,并在此基础上开展3~7层CFRP布对煤圆柱力学特性及能量演化的影响研究。结果表明:煤圆柱的屈服点与峰值点随CFRP层数增加而渐进重合,呈现毫无征兆的屈服即破坏状态;随着CFRP层数增加,煤圆柱峰值强度增幅呈现先增大后减小,得到了表征不同层数下CFRP约束煤样峰值强度增幅演化规律的函数,峰值应变增幅呈现先增加后减小,而后再增加又减小的规律;弹性应变能恒定时,煤圆柱轴向应变与CFRP层数无相关性,但其峰值应变与极限应变均随CFRP层数增加而增大;峰值点耗散能转化率随CFRP层数增加呈现先增大而后减小规律,建立了表征不同层数下CFRP约束煤圆柱耗散能转化率演化规律的函数;从应力-应变曲线延性特征、峰值强度增幅、峰值应变增幅、耗散能转化率及总能量增幅等5方面综合考虑,兼顾经济成本与缠绕水平原则,确定3层为CFRP约束煤圆柱的最优缠绕层数。

In order to study the effect of CFRP layers on the mechanical properties of coal cylinders.A discrete-continuous coupled mesomechanical numerical model of CFRP passively confined coal cylinders was developed using a three-dimensional FLAC-PFC coupling method.The validity of the model was verified with experimental data of 0-2 layers of CFRP passively confined coal cylinders.On this basis,studies of the influence of 3-7 layers on mechanical properties and energy evolution of CFRP confined coal cylinders was carried out.The results show that the yield limit and the peak of the coal cylinders gradually coincide with the increase of CFRP layers,showing a state of yielding or failure without warning.With the increase of CFRP layers,the increment in the peak strength of coal cylinders first increases and then decreases.A function is obtained to characterize the evolution of the peak strength increment of CFRP confined coal cylinders under different layers.The increment in the peak strain shows a behavior of first increasing and then decreasing,and then increasing and decreasing again.When the elastic strain energy is constant,the axial strain of the coal cylinders has no correlation with CFRP layers,but its peak strain and ultimate strain both increase with the increase of CFRP layers.The dissipative energy conversion ratio at peak point increases first and then decreases with the increase of CFRP layers.A function is established to characterize the evolution of the dis sipative energy conversion ratio of CFRP confined coal cylinders with different layers.The ductility characteristics of stress-strain curves,peak strength increment,peak strain increment,dissipative energy conversion ratio and total energy increment of coal cylinders are considered comprehensively,and taking into account the principles of economic cost and winding level,the three layers are determined as the optimal winding layers for CFRP confined coal circular-columns.