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首页> 外文期刊>Journal of engineering materials and technology >Size Effect and Fracture Characteristics of Composite Laminates
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Size Effect and Fracture Characteristics of Composite Laminates

机译：复合材料层合板的尺寸效应和断裂特性

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摘要

Measurements of the size effect on the nominal strength of notched specimens of fiber composite laminates are reported. Tests were conducted on graphite/epoxy crossply and quasi-isotropic laminates. The specimens were rectangular strips of widths 6.4, 12.7, 25.4 and 50.8 mm (0.25, 0.50, 1.00 and 2.00 in.) geometrically similar in two dimensions. The gage lengths were 25, 51, 102 and 203 mm (1.0, 2.0, 4.0 and 8.0 in.). One set of specimens had double-edge notches and a [0/92_2]_s crossply layup, and another set had a single-sided edge notch and a [0/ ± 45/90]_s quasi-isotropic layup. It has been found that there is a significant size effect on the nominal strength. It approximately agrees with the size effect law proposed by Bazant, according to which the curve of the logarithm of the nominal strength versus the logarithm of size represents a smooth transition from a horizontal asymptote, corresponding to the strength criterion (plastic limit analysis), to an inclined asymptote of -0.5 slope, corresponding to linear elastic fracture mechanics. Optimum fits of the test results by the size effect law are obtained, and the size effect law parameters are then used to identify the material fracture characteristics, particularly the fracture energy and the effective length of the fracture process zone. Finally, the R-curves are also identified on the basis of the maximum load data. The results show that in design situations with notches or large initial traction-free cracks the size effect on the nominal strength of fiber composite laminates must be taken into account.
机译：报告了尺寸对纤维复合材料层压板缺口试样标称强度的影响的测量结果。测试是在石墨/环氧树脂交叉层和准各向同性层压板上进行的。样品是矩形条，在二维上在几何上相似，宽度分别为6.4、12.7、25.4和50.8毫米（0.25、0.50、1.00和2.00英寸）。标距长度为25、51、102和203毫米（1.0、2.0、4.0和8.0英寸）。一组标本具有双边缘槽口和[0 / 92_2] _s交叉叠层，另一组标本具有单面边缘槽口和[0 /±45/90] _s准各向同性叠层。已经发现，对标称强度有明显的尺寸影响。它近似符合Bazant提出的尺寸效应定律，根据该定律，标称强度的对数与尺寸的对数的曲线表示从水平渐近线（对应于强度标准）的平稳过渡（塑性极限分析）到-0.5斜率的渐近线，对应于线性弹性断裂力学。通过尺寸效应定律获得最佳的测试结果拟合，然后使用尺寸效应定律参数确定材料的断裂特性，尤其是断裂能和断裂过程区的有效长度。最后，还根据最大载荷数据确定R曲线。结果表明，在存在缺口或较大的无初始牵引裂纹的设计情况下，必须考虑尺寸对纤维复合材料层压板标称强度的影响。

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