Flow-induced buckling and post-buckling vibration characteristics of composite pipes in thermal environment

Abstract

Static and dynamic characteristics of the composite pipe conveying super-critical fluid in thermal environment are studied in the present work, with the aim of providing theoretical basis on the design and improvement of the composite pipes in post-buckling status. Based on Euler-Bernoulli beam theory, the nonlinear equation of motion of the composite pipe is derived and is then solved employing an analytical method. Subsequently, parametric study is performed to evaluate the effects of the fiber orientation angle, external temperature and internal fluid velocity on the statics and dynamics of composite pipes around both the first and the second buckled configurations. Thermal contraction and thermal expansion characteristics of the composite materials are both considered corresponding to different fiber orientation angles. The results indicate that, pipes with larger fiber orientation angles are easier to lose stability in the form of buckling and have larger static buckling displacements. For dynamic analysis, around the second buckled configuration, the first vibration mode of the pipe vanishes, with the second mode being the lowest one. Additionally, the temperature and internal fluid velocity have great influence on the post-buckling natural frequencies and mode-shapes of the composite pipe, which result in complex mode change phenomenon.