Statistical Evaluation of Effect of Shape Imperfections on Buckling Load of Carbon Fiber-Reinforced Plastic Thin-Walled Cylinders

Abstract

Thin-walled cylinders made from carbon fiber-reinforced plastic (CFRP) were measured using a laser displacement sensor and subjected to load tests. The effects of shape imperfections in the circumferential and axial directions, the radius–thickness ratio (r/t), and the offset compression loads on the knockdown factor (KDF), which is the ratio of the experimental and theoretical buckling loads, were investigated. A statistical evaluation of various trends relating to the KDF and the amplitudes of the shape imperfections was conducted. The buckling load test on the cylinders showed large deviations and scatter between theory and experiment. It is known that shape imperfections are one of the key factors affecting KDF. The shape imperfection induces a local stress concentration and/or local buckling, and they may induce premature buckling. We found a correlation between the KDF and shape imperfections in the circumferential and axial directions and r/t. The KDF did not have a simple correlation with the direction of offset compression loads, the direction of the maximum and minimum amplitude of local shape imperfections, or offset distance.

Keywords

• buckling
• thin-walled cylinders
• knockdown factor