单纤维段试验中载荷传递机理的微观力学分析

提出了一种新的、单纤维段埋入法(SFFM)试验中载荷传递机理的微观力学模型。当纤维/树脂界面所受到的剪切应力超过了界面的粘结剪切强度后,界面将发生脱粘,并且脱粘裂纹将沿着界面扩展。以Weibull模型来模拟纤维轴向拉伸强度的统计分布。讨论了纤维轴向拉伸强度以及界面粘结剪切强度对复合材料各组分内部应力分布的影响。认为在给定复合材料各相的弹性常数和几何参数后,根据不同的纤维轴向拉伸强度以及界面性能(包括界面粘结剪切强度、界面的摩擦系数和基体的径向压力),可以将单纤维段试验中纤维/树脂界面的状态清楚地分为三类:1)完全粘结界面;2)部分粘结界面;3)完全摩擦界面。给出了单纤维段试验过程中界面处于上述三种状态下时,所必须满足的一些条件。最后,还给出了极限纤维段长度的一个合理的定义,并说明该长度是由粘结纤维长度和脱粘纤维段长度所构成。

Micromechanis Analysis of Load-transfer Mechanism is Single-fibre Fregmentation Test

The paper presented a new micomechanics load-transfer model for single-fibre fragmentation test. The interfacial shear streength and the crack will develop along the interface. The fibre stochastic strength distribution was modelled by a two-parameter Wibull distribution. The influence of the interfacial bonding strength and fibre axial-tensile strength on stress states in components of composites was discussed. The interfacial state during the fragmentation process may be one of following three states. 1) fully bonding;2) partial bonding; 3) fully debonding, according to the fibre axialtensile strength and interfacial properties (including interfacial bounding shear strength,interfacial friction coefficient and matrix radial pressure) after elastic constants and geometrical parameters of composites phases are given. The necessary conditions for these three states were discussed. Finally,a suitable definition of the critical fibre length was given and the critical length was constrouted by two parts-debonding fibre length and bonding fibre length.