Free vibration analysis of delaminated beam with two surface cracks

• Main Author: Ho, Jim Zhow.
• Other Authors: Shu Dong Wei
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Mechanical engineering::Mechanics and dynamics
• Online Access: http://hdl.handle.net/10356/54151
• Institution: Nanyang Technological University

In the modern world, there is an increase demand in the usage of beams in the engineering industry. Compsite beam are mainly used in the manufacturing of aerospace, marine and civil structure and machinery because of their exceptional mechanical properties such as strength and stiffness. The formation of defects such as delamination and crack can adversely reduce the mechanical properties and this in turn can lead to catastrophic failure if such defects are not detected promptly. There have been several researches that revolve solely around the dynamic effects of delamination of beams, or the dynamic effects of cracks on beams. But there is a lack of researches into the dynamic effects of cracks in addition to the delamination of beam. In this report, the author presents analytical solutions to the dynamic effects of cracks in addition to delamination in beams. The Euler-Bernoulli beam theory has been adopted together with the “Free Mode” model to study the free vibration of delaminated beam with cracks. Analytical solution has been carried out on the effects of in 3 possible scenarios with a delaminated beam with symmetrical cracks. Several parameters such as the depth of crack with respect to the delamination length and the location of the cracks with respect to the length of the delamination are investigated to provide insights into the effects on the mechanical properties of the beams. Comparative studies on this 3 scenario reveal that there is a sizable difference in the behaviour of the natural frequencies of the delaminated beam. By and large, the study reveals that the existence of cracks will amplify the unfavourable effects of delamination on the beams. The natural frequency will decrease which imply that the stiffness of the beam will decrease. The results and discussions can serve as a point of reference for future researches and as well as development of other numerical solution.