Araújo F S, Nunes L C S
Laboratory of Opto-Mechanics (LOM), Department of Mechanical Engineering (PGMEC-TEM), Universidade Federal Fluminense-UFF, Rua Passo da Patria, 156, Bloco E, Sala 210, Niteroi, RJ CEP 24210-240, Brazil.
Soft Matter. 2020 Sep 14;16(34):7950-7957. doi: 10.1039/d0sm00745e. Epub 2020 Aug 7.
The aim of this work was to investigate the shear and lateral normal responses of a soft unidirectional fiber-reinforced material subjected to simple shear. The Poynting effect was also investigated. Soft composites were manufactured from a flexible adhesive reinforced by a single family of parallel and continuous fibers of nylon. Specimens with fibers oriented at an angle (-45°, 0°, 45° and 90°) with respect to the applied shear force were tested. A simple shear test apparatus was developed to measure shear and normal forces simultaneously. A standard reinforcing model based on strain-energy density function was used to verify the mechanical behavior of the soft composite with different fiber orientation. Results showed that the initial stiffness of the composite with fibers oriented at -45° and 45° was approximately the same and was higher than those at 0° and 90°. Also, there was no significant difference between values of initial stiffness for angles of 0° and 90° and the neat matrix. The effect of the stretching resistance of the fibers was more pronounced for fibers oriented at 45° and 90°. There was no Poynting effect for the neat matrix or for the composite with fibers at 0° while positive and negative Poynting effects were observed for fibers oriented at -45° and 45° (and 90°), respectively. The standard reinforcing model was only verified for a limited range of amount of shear due to composite failure. Fiber debonding and fiber buckling were observed in the composites with fibers oriented at 45° (and 90°) and -45°, respectively, at large deformations.
这项工作的目的是研究一种柔软的单向纤维增强材料在简单剪切作用下的剪切和横向法向响应。同时还研究了泊松效应。柔软复合材料由一种柔性粘合剂制成，该粘合剂由单一组平行且连续的尼龙纤维增强。对纤维相对于施加的剪切力成一定角度（-45°、0°、45°和90°）取向的试样进行了测试。开发了一种简单剪切试验装置来同时测量剪切力和法向力。基于应变能密度函数的标准增强模型用于验证不同纤维取向的柔软复合材料的力学行为。结果表明，纤维取向为-45°和45°的复合材料的初始刚度大致相同，且高于0°和90°时的刚度。此外，0°和90°时的初始刚度值与纯基体之间没有显著差异。纤维的拉伸阻力对取向为45°和90°的纤维影响更为明显。纯基体或纤维取向为0°的复合材料没有泊松效应，而对于取向为-45°和45°（以及90°）的纤维，分别观察到正泊松效应和负泊松效应。由于复合材料失效，标准增强模型仅在有限的剪切量范围内得到验证。在大变形时，分别在纤维取向为45°（以及90°）和-45°的复合材料中观察到纤维脱粘和纤维屈曲。
