Vibration analysis of composite airframe structural elements

点击翻译按钮获取中文摘要

Making more comfortable, low cost, environmentally friendly aircraft is the goal of the aeronautical designers for the next generation commercial fleets. Fibre-Reinforced Plastics (FRPs) play a key role in the achievement of these tasks, allowing considerable weight savings and improvements in payload, owing to their favourable specific properties. A further advantage has been devised in the laminar structure of these materials, when the needs for noise and vibration damping, directly influencing comfort, have been faced; rubbery layers can be integrated into the laminate structure during the fabrication process, and their damping properties exploited by subjecting them to high shear deformations in service. Delamination is probably the most frequently occurring damage in composite laminates due to its weak interlaminar strength. Delaminations may develop from small cracks due to either imperfect fabrication processes or impact during service. The presence of the delaminations is known to cause strength and stiffness degradation, as well as changes of the vibration characteristics of the laminates. All defects, in general, and delaminations, in particular, reduce the natural frequency, which may cause resonance if the reduced frequency is close to the working frequency. It is imperative that we should be able to predict the changes in the frequency, as well as the mode shape, in a dynamic environment. The overall aim of my research program is to improve our understanding of the structural dynamics and vibration associated with airframe structures, in general, and the intact and damaged/ defective laminated composite/sandwich structural elements, in particular. The desired outcome is 3-fold: To provide knowledge, models and powerful tools, which will give a better understanding of the problems associated with the damages, the vibrational behaviour of laminated composites and the effects of damage on structural behaviour; To develop enhanced and cost efficient analytical, semi-analytical and numerical models and a dedicated modal analysis tool for desired precision; and last but not least, to train HQP in the field of structural dynamics/vibration and composites which will continue to grow in demand for many years to come.