Analysis of the effect of the direction of reinforcement of a fibrous composite material on the inhomogeneity of localization of deformations and stresses using the method of thermoelastic response

R. Akhmetkhanov
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Abstract

The purpose of the article is to study the effect of the direction of reinforcement of a composite material relative to the cyclic load on the inhomogeneity of stress distribution by the thermal method of non-destructive testing using the thermoelastic effect. This method is widely used in all industries for the control of structural elements and in research work. The degree of stress inhomogeneity is used when choosing the safety factors necessary to ensure the safety of technical objects. In this study, the thermoelastic effect is used to show the possibility of estimating the local distribution of stresses using the temperature field of the test object, proceeding from the linear relation between the temperature of the elastic body and mechanical stresses. The results of studying composite laminates (fibrous filler (fiberglass) with an epoxy matrix) with different laying of fibers with respect to the direction of loading are presented. Four laminate samples were considered: single-layer [0] and [90], three-layer [0]3 and [90]3. Statistical data and estimates of the coefficients of variation, methods of clustering and averaging over the length of the laminates the values of the temperature distribution over the surface of the laminates. The numerical characteristics of the distribution of local temperatures are obtained. It is shown that a more uniform distribution occurs when reinforcing is directed along the direction of the material loading. The integral and local characteristics of the temperature distribution in the samples are compared. The differences in the local temperature distribution depending on the laminate thickness were noted visually for single-layer and three-layer samples. A more uniform distribution of the load is also observed in the direction of reinforcement and with an increase in the number of reinforcement layers. The results obtained lead to the conclusion that the choice of the value of the safety factor, which evaluates the level of stress inhomogeneity, depends on the design features of the laminates. During operation of products made of composite materials in the presence of significant accumulated damage, when the uneven distribution of stresses increases, the levels of safety factors should be adjusted.
利用热弹性响应方法分析纤维状复合材料的加固方向对变形和应力局部不均匀性的影响
文章的目的是利用热弹性效应,通过热无损检测方法研究复合材料相对于循环载荷的加固方向对应力分布不均匀性的影响。这种方法被广泛应用于各行各业的结构元件控制和研究工作中。应力不均匀程度用于选择必要的安全系数,以确保技术对象的安全。本研究利用热弹性效应,从弹性体温度与机械应力之间的线性关系出发,展示了利用测试对象的温度场估算局部应力分布的可能性。本文介绍了对纤维相对于加载方向不同的复合层压板(纤维填充物(玻璃纤维)与环氧树脂基体)的研究结果。研究了四种层压板样品:单层 [0] 和 [90]、三层 [0]3 和 [90]3。层压板表面温度分布值的统计数据和变异系数估计值、聚类方法和层压板长度上的平均值。获得了局部温度分布的数值特征。结果表明,沿材料加载方向加固时,温度分布更均匀。比较了样品中温度分布的整体特征和局部特征。在单层和三层样品中,可以直观地看到局部温度分布的差异取决于层压板的厚度。此外,随着加固层数的增加,加固方向上的载荷分布也更加均匀。根据所获得的结果可以得出结论,安全系数值的选择取决于层压板的设计特点,而安全系数可以评估应力不均匀的程度。在复合材料制成的产品运行过程中,如果存在严重的累积损坏,应力分布不均匀程度增加,则应调整安全系数的水平。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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