Size effect on elastic stress concentrations in unidirectional fiber reinforced soft composites
Size effect on elastic stress concentrations in unidirectional fiber reinforced soft composites
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DOI：
10.1016/j.eml.2019.100573
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发表时间：
2019-11-01
影响因子：
4.7
通讯作者：
Phoenix, S. Leigh
中科院分区：
文献类型：
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作者：
Hui, Chung-Yuen;Liu, Zezhou;Phoenix, S. Leigh
我们重新审视了平面单向纤维基复合材料中多个横向排列的纤维断裂在相邻纤维上的应力集中的经典问题。假定纤维与弹性基体完美结合。通过改变复合材料的总长度相对于断裂和完整纤维之间的特征载荷传递长度，研究了有限尺寸对应力集中的影响。作为对Hedgepeth经典分析中离散纤维和基体框架的替代，以及Hikami和Chou对其进行的扩展，纤维在复合材料中的应力分布是通过将复合材料作为一个高度各向异性的弹性板进行连续建模得到的，在离散模型中纤维位置的应力和应力集中因子以封闭形式提取出来。对于有限长度的复合材料，用连续介质模型确定的应力集中系数与离散剪切滞后模型的数值解相比较具有优势。在无限长纤维板的极限情况下，我们的应力集中系数也与Hikami和Chou的精确结果吻合得很好。对于长度小于特征弹性载荷传递长度的复合材料，并在位移边界条件下加载，我们表明，无论裂纹的大小或纤维断裂的数量如何，局部应力集中都会消失。这种行为在模拟和解释实验室实验中对最近的软复合材料样品的力学行为时变得重要，这些样品由极柔顺的弹性矩阵中的刚性纤维组成。(C) 2019 Elsevier Ltd.版权所有。
We revisit the classic problem of determining stress concentrations on neighboring fibers to multiple, transversely-aligned fiber breaks in a planar, unidirectional fiber-matrix composite. Fibers are assumed to be perfectly bonded to the elastic matrix. Finite size effects on stress concentration are studied by varying the overall length of the composite relative to the characteristic load transfer length between broken and intact fibers. As an alternative to the discrete fiber and matrix framework in the classic analysis of Hedgepeth, and its extension by Hikami and Chou, the fiber stress distribution in the composite is obtained through continuum modeling of the composite as a highly anisotropic elastic plate, whereby the stresses and stress concentration factors at fiber locations in the discrete model are extracted in a closed form. For composites of finite length, the stress concentration factors determined using the continuum model compare favorably with numerical solution of the discrete shear-lag model. In the limit of a plate with infinitely long fibers, our stress concentration factors also agree well with the exact results of Hikami and Chou. For composites having a length less than the characteristic elastic load transfer length, and loaded under displacement boundary conditions, we show that local stress concentrations vanish irrespective of the size of the crack or the number of fiber breaks. This behavior becomes important when modeling and interpreting laboratory experiments on the mechanical behavior of recent soft composite specimens consisting of stiff fibers in an extremely compliant elastic matrix. (C) 2019 Elsevier Ltd. All rights reserved.