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Holographic Interferometry Measurement and Theoretical Analysis of Deformations of Composite Laminates due to Interlaminar Stresses

复合材料层合板层间应力变形的全息干涉测量与理论分析

基本信息

批准号：
01420019
负责人：
KONDO Kyohei
金额：
$ 7.3万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (A)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

项目摘要

Deformations due to the interlaminar stresses in the composite laminates subjected to the uniform mechanical and hygrothermal loadings were investigated in order to understand the mechanism of the delamination which is one of the most frequently observed fallure modes of the laminates.By the quasi three-demensional finite element method, the deformations in the vicinity of the free edges or the transverse crack tips were analyzed assuming that the stresses do not vary along the direction of the free edge or the transverse crack. The superposition method was proposed where the free edge problem and the transverse crack tip problem are transformed to the superpositions of the infinite laminate under uniform stresses and the configurations with external loads applied on the free edge surface and the transverse crack surface, respectively. The superposition technique can eliminate the deformations not resulting from the interlaminar stresses.By the holographic interferometry, the deformations of the graphite-epoxy laminates coupons under the pure bending moment or the uniform tensile load were measured. The delaminations were introduced by the cyclic tensile loading at the free edges. The overall deformations by the bending moment coincided with the theoretical predictions for the deformations of the infinite laminates based on the classical lamination theory. The deformation near the free edges due to the interlaminar stresses could not be detected since they were small compared to the overall bending deformations. The deformation near the free edges due to the interlaminar stresses in the laminates under the tensile loads were observed for the coupons with delaminations, verifying the numerical results by the finite element method.

研究了复合材料层合板在均匀机械和湿热载荷作用下由于层间应力而产生的变形，以了解分层的机理，这是层合板最常见的失效模式之一。通过准三维有限元方法，假设应力不存在，则分析了自由边缘或横向裂纹尖端附近的变形。沿自由边或横向裂纹的方向变化。提出了叠加方法，将自由边问题和横向裂纹尖端问题分别转化为均匀应力下无限层合板和自由边表面和横向裂纹表面施加外部载荷的构型的叠加。叠加技术可以消除非层间应力引起的变形。通过全息干涉测量技术，测量了石墨-环氧树脂层压板试片在纯弯矩或均匀拉伸载荷作用下的变形。分层是由自由边缘处的循环拉伸载荷引起的。弯矩引起的整体变形与基于经典层合理论的无限层合板变形的理论预测一致。由于层间应力导致的自由边缘附近的变形无法检测到，因为与整体弯曲变形相比，它们很小。对于有分层的试样，观察了在拉伸载荷作用下层压板中层间应力导致的自由边缘附近的变形，并通过有限元方法验证了数值结果。