Homogenization Analysis and Experimental Verification for Creep of Unidirectional Fiber Reinforced Composites

单向纤维增强复合材料蠕变均匀化分析及实验验证

基本信息

批准号：
09450046
负责人：
OHNO Nobutada
金额：
$ 1.34万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09450046/
关键词：
Composite Material Creep Homogenization Theory Periodic Structure

项目摘要

1. A homogenization theory was formulated for time-dependent nonlinear composites with periodic internal structures, so that perturbed displacement rate is decomposed into time-independent elastic and time-dependent viscoplastic parts. Then a macroscopic constitutive relation and a microscopic evolution equation of stress were derived.2. The theory mentioned above was applied to analyzing transverse creep and elastic-viscoplastic deformation of unidirectional composites reinforced with continuous fibers. Assuming the plane strain condition in the fiber orientation, and employing the square and hexagonal arrays of fibers, it was shown that the square and hexagonal arrays exhibit significant and negligible anisotropy in macroscopic behavior, respectively.3. The field of perturbed displacement rate was discussed by assuming the point symmetry of internal distributions with respect to a cell center. It was thus shown that the field of perturbed displacement rate is point-symmetric with respect to cell facet centers as well as the cell center, and that perturbed displacement rate vanishes at these centers. This finding led to introducing a semiunit cell, on the boundary of which the point symmetry is imposed on perturbed displacement rate as its boundary condition.4. The present theory was employed to analyze off-axial elastic-viscoplastic deformation of a hexagonally fiber-arrayed composite. It was then found that a small off-axis angle gives rise to significant decrease of viscoplastic flow stress, but that viscoplastic flow stress changes little for off-axis angles larger than 45 degree.5. Comparison of the analytical result mentioned above with experimental results on a hybrid composite GLARE 2 showed that the dependence of elastic-viscoplastic behavior on off-axis angle revealed in the present analysis is observed experimentally.

1. 针对具有周期性内部结构的时变非线性复合材料，建立了均质化理论，将扰动位移速率分解为与时间无关的弹性部分和与时间相关的粘塑性部分。推导了应力的宏观本构关系和微观应力演化方程。 2．将上述理论应用于分析连续纤维增强单向复合材料的横向蠕变和弹粘塑性变形。假设纤维取向的平面应变条件，并采用正方形和六边形纤维阵列，结果表明，正方形和六边形阵列在宏观行为上分别表现出显着和可忽略不计的各向异性。 3．通过假设内部分布相对于单元中心点对称来讨论扰动位移率场。由此可知，扰动位移率场相对于单元面中心以及单元中心呈点对称，并且扰动位移率在这些中心处消失。这一发现导致引入半晶胞，在其边界上施加扰动位移速率的点对称性作为其边界条件。4．本理论用于分析六边形纤维阵列复合材料的离轴弹粘塑性变形。结果发现，较小的离轴角会使粘塑性流应力显着降低，但当离轴角大于45°时，粘塑性流应力变化不大。5．将上述分析结果与混合复合材料 GLARE 2 的实验结果进行比较表明，本分析中揭示的弹粘塑性行为对离轴角的依赖性是通过实验观察到的。