Relaxation behavior of clamping force in bolted joints of pultruded GFRP laminates
Relaxation behavior of clamping force in bolted joints of pultruded GFRP laminates
复制标题
拉挤 GFRP 层压板螺栓连接夹紧力的松弛行为
DOI：
10.2472/jsms.59.540
复制
发表时间：
2010
期刊：
影响因子：
--
通讯作者：
I. Nishizaki
中科院分区：
文献类型：
--
作者：
T. Kishima;Toshio Katsuno;K. Kobayashi;S. Hino;I. Nishizaki
摩擦型FRP螺栓连接夹紧力的松弛行为是FRP应用于结构中的重要课题之一。本文的目的是在试验结果的基础上，得到GFRP螺栓连接松弛行为的影响因素。钢锚杆和玻璃钢复合材料都有松弛行为。钢螺栓在初始加载后立即主导松弛力，而不是重新加载。考虑到实验结果中观察到的复合层合板弛豫力的变化以及复合层合板比单层层合板更大的弛豫力，除基体聚合物外，GFRP层合板的弛豫因子可以是层合板表面几何形状和层合键。玻尔兹曼叠加原理很难适用于初始加载和再加载时的松弛力，说明螺栓螺纹可通过剪切塑性变形使截面面积减小而产生应变硬化，从而获得较小的再加载松弛力，考虑到基体聚合物的粘塑性特性，可通过塑性和不可逆的粘性变形来改变表面几何形状。距离平面较远的曲面几何形状可以获得更多的松弛力，并且可以将曲面几何形状分为具有等高度凸起的曲面和具有随机高度凸起的曲面。层合键的松弛力占主导地位，其较低的粘度可以使松弛力更大。与基体聚合物相比，层压板的黏度变化更大，并通过塑性和不可逆的粘性变形对结构进行改性而增加黏度。在最短的时间内可以完成平坦表面的松弛行为，并且粘合剂粘度与基体聚合物一样高。
The relaxation behavior of clamping force in friction-type FRP bolted joints is one of the significant subjects in application of FRP to structures. The aim of this paper is to obtain the factors of relaxation behaviors in the GFRP bolted joints based on the experimental results. The relaxation behaviors are due to both steel bolt and GFRP laminate. Steel bolt dominates the relaxed force immediately after initial loading but not reloading. The relaxation factors of GFRP laminate except matrix polymer could be both laminate surface geometry and laminate bond, considering the variance of relaxed force and more relaxed force for bonded laminate than single laminate observed in the experimental results. Boltzmann superposition principle can be hardly applicable to the relaxed forces for initial loading and reloading, suggesting that less relaxed force for reloading could be obtained by the strain hardening of bolt threads through the decrease of cross section area due to shear plastic deformation and that surface geometry could be modified by plastic and irreversible viscous deformation considering the viscoplastic property of matrix polymer. More relaxed force could be obtained for the surface geometry farther from the flat surface and the surface geometries could be categorized into the surface with either equal height protuberances or random height ones. Laminate bond dominates the relaxed force and its lower viscosity could give relaxed force more. The viscosity of laminate bond could be more variable than matrix polymer and increase through the modification of structure by plastic and irreversible viscous deformation. The minimum elapsed time could be required to complete the relaxation behavior for the flat surface and the bond viscosity as high as matrix polymer.