A buckling test of composite cylindrical shells with a radius–thickness ratio (r/t) = 893 under axial compression was conducted to investigate the effects of the radius–thickness ratio (r/t). It is known that the buckling load of cylinders shows large differences and scatter between theory and experiment. The ratio of the experimental buckling load and theoretical buckling load is called the knockdown factor (KDF). Many investigations have been conducted to find the cause of the degradation and scatter in the KDF, but as yet, no cause has been found. In 1968, NASA’s buckling design criterion, NASA SP-8007, gave an empirical KDF curve that decreased with the increasing r/t (up to 2000) for metal cylinders. The same curve has been applied to composite cylinders. Recently, Takano derived a flat lower-bound KDF in terms of A- and B-basis values (99% and 90% probability with a 95% confidence level) through a statistical analysis of experimental buckling loads. The result, however, based on experimental results up to r/t = 500 and, thus, the dependency on a large range of r/t, is not clear. Thus, the authors focused on a larger range of r/t. Cylindrical shells made from carbon fiber-reinforced plastic (CFRP) were tested. The nominal radius, thickness, and length were r = 100.118 mm, t = 0.118 mm, and L = 200 mm and, thus, the r/t = 848 and length-to-radius ratio (L/r) = 2.0. Shape imperfections were also measured by using in-house laser displacement equipment. The buckling load was slightly affected by the r/t, but the reduction in the KDF was insignificant.

中文翻译：

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大半径比的复合圆柱壳的屈曲试验

进行了半径-厚度比（r / t）= 893的复合圆柱壳在轴向压缩下的屈曲试验，以研究半径-厚度比（r / t）的影响。众所周知，圆柱的屈曲载荷在理论和实验之间显示出很大的差异和分散。实验屈曲载荷与理论屈曲载荷之比称为击倒系数（KDF）。已经进行了许多调查以发现KDF降解和散布的原因，但是至今尚未找到原因。1968年，NASA的屈曲设计标准NASA SP-8007给出了经验KDF曲线，该曲线随着r / t的增加而减小（最多2000个）用于金属圆柱体。相同的曲线已应用于复合材料圆柱体。最近，高野通过对实验屈曲载荷的统计分析得出了基于A和B基值（99％和90％的概率，置信度为95％）的平坦的下界KDF。然而，基于高达r / t = 500的实验结果得出的结果尚不清楚，因此，对大范围r / t的依赖性尚不清楚。因此，作者集中于更大的r / t范围。测试了由碳纤维增强塑料（CFRP）制成的圆柱壳。标称半径，厚度和长度分别为r = 100.118毫米，t = 0.118毫米和L = 200毫米，因此r / t = 848，长径比（L / r）= 2.0。还使用内部激光位移设备测量了形状缺陷。屈曲载荷受r / t的影响很小，但KDF的降低并不明显。