Vibration Modelling and Analysis of Intact and Defective Composite Airframe Structural Elements

点击翻译按钮获取中文摘要

Air transportation currently supports 56.6 million jobs worldwide and economic activity equivalent to 3.5% of the global GDP1, carries 2.6B passengers a year, with the volume of air traffic expected to grow 2.6-fold in the next 20 years2. Conversely, there are growing concerns about the increasing environmental impacts of aviation, making the social need for more environmentally friendly aircraft greater than ever. Also, environmental performance is becoming an increasingly important factor in market competitiveness. ***Composites, including Fiber-Reinforced Plastics (FRPs) and Fiber-Metal laminates (FML), play a key role in the achievement of these tasks, allowing considerable weight savings and improvements in payload, owing to their favorable specific properties. Also, noise and vibration attenuation, directly influencing passenger comfort, can be achieved by integrating layers of dampening materials into the laminate structure. Glass fiber composites are also material of choice for the production of wind turbine blade due to their high stiffness and relatively low cost, and carbon fiber is used as reinforcement for advanced composites. *** Delamination and crack are probably the most frequently occurring defects in composite laminates. Delamination may develop from small cracks due to either imperfect fabrication processes or impact during service. The presence of the delamination is known to cause strength and stiffness degradation and changes in the vibration characteristics of the laminates. All defects, in general, and delamination, in particular, reduce the structural stiffness and consequently natural frequency of the system, which may cause resonance if the reduced frequency is close to the working frequency. It is imperative to be able to predict the changes in the frequencies and mode shapes in a dynamic environment.*** The overall aim of my research program is to improve our understanding of the structural dynamics/vibration associated with airframe structures, in general, and the intact and defective laminated composite structural elements, in particular. The desired outcome is 4-fold: To gain a better insight into the problems associated with the damages, the vibrational behavior of laminated composites and the effects of damage on structural behavior; To develop novel enhanced and cost efficient (semi-)analytical and highly convergent numerical models and dedicated modal analysis tools for desired precision and accuracy of results; To develop a scheme capable of predicting the critical number/size/location of defects, critical to fault-tolerant/fail-safe designs; and finally, to train HQP in the field of structural dynamics/vibration and composites, continuing to grow in demand for many years to come.******1ATAG “Aviation: benefits beyond borders (2012)”, estimation based on 2010.***2JADC “Worldwide Market Forecast For Commercial Air Transport 20122031” (2012)