基于弹性-塑性内聚力模型的纤维拔出界面宏观行为分析

用解析法分析了单纤维从聚合物基体中的拔出过程,采用弹性—塑性内聚力模型模拟裂纹的扩展和界面失效,确定了临界纤维埋入长度,该值区分两种不同长度的纤维拔出过程. 在纤维拔出过程,界面经历不同的阶段. 纤维埋长小于临界长度时,界面的脱粘载荷与纤维的埋长成正比;超过临界长度后,界面的脱粘载荷近似为常数. 分析了界面参数对脱粘载荷的影响:增加界面的剪切强度和界面的断裂韧性,或减小界面裂纹萌生位移,均能提高界面的脱粘载荷;界面脱粘后无界面摩擦应力时,拔出载荷—位移曲线的峰值载荷等于界面的脱粘载荷;界面摩擦应力存在时,使峰值载荷大于脱粘载荷,需要较长的纤维埋入长度和较大的界面摩擦应力.

ANALYSIS OF THE MACROSCOPIC INTERFACIAL BEHAVIOUR OF THE FIBRE PULLOUT USING ELASTIC-PLASTIC COHESIVE MODEL

A single fibre pullout behavior from polymer matrix was analytically investigated in this paper. The elastic-plastic cohesive zone model was employed to simulate the crack propagation and interfacial failure. The critical fibre embedded length is determined, which distinguishes two pull-out processes from different fibre embedded lengths. There are different interface states during the fibre pull-out process. When the fibre embedded length is shorter than the critical length, the debonding force for the interface is linear relationship to the fibre embedded length; while the debonding force is approximately constant if the fibre embedded length excesses the critical length. The influence of the interfacial parameters on the debonding force is studied. Increasing the interfacial shear strength and the interface fracture toughness, or decreasing the displacement of crack initiation, can raise the debonding force for the interface. Without the interfacial frictional shear stresses after interfacial debonding, the peak load in the pullout force-displacement curve equals the debonding force for the interface. Under the influence of interfacial frictional shear stress, longer fibre embedded length and larger interfacial frictional shear stress lead to the peak load exceeding the debonding force.