报告一题目：Enhanced metal-composite adhesive bonding using nanowire arrays
报告二题目：Fatigue life uncertainty of adhesively bonded composite scarf joints – An airworthiness perspective
报告人：A/Prof. Akbar Khatibi (Royal Melbourne Institute of Technology University)
主办单位 : 国际合作处、科协、机械结构力学及控制国家重点实验室、航空宇航学院
The ever-increasing demand for high performance materials with better mechanical properties and reduced weight compared to traditional monolithic metals has led to a surge in composite materials within the aircraft industry. Fibre metal laminates (FMLs) are hybrid materials composed of alternating layers of metal and fibre reinforced polymer (FRP) composites developed for this purpose. These materials combine the properties of both the metal and FRP layer and have many benefits compared to metal alloys including high strength, high fatigue resistance, low density and hence low weight, high resistance to corrosion and good impact resistance. Although the in-plane properties of FMLs show great promise, their through-thickness properties need enhancement. Due to weak bonding between the metal and composite layer, fibre metal laminates are prone to failure along the interface between metal and composite layer leading to catastrophic results. The aim of this research is to enhance the bonding between the metal and composite layers, thereby increasing the through-thickness property of FMLs using nano-bonded metallic nanowire interleaves which combine the novel techniques of nano-bonding and interleaving. In addition to gaining a better understanding of the mechanisms involved in the nano-bonding of nanoparticles with a fibre-like structure, within themselves and with metal substrates, this research project will develop FMLs with enhanced bonding between the metal and composite layer and improved through-thickness properties.
Adhesively bonded repairs can provide a highly structurally-efficient and cost-effective means of restoring residual strength to aircraft components. However, gaining airworthiness approval for bonded repairs to primary structures is a significant problem. This is largely because of the failure of current non-destructive inspection techniques to detect weak or non-durable adhesively bonded joints. Due to the presence of undetectable defects and anomalies, recent airworthiness policy ignores the contribution of adhesively bonded joints to the fatigue durability of repaired load-carrying aircraft structures. The key requirement for airworthiness is to demonstrate an acceptable low probability of repair patch disbonding during the remaining life of the structure. In order to satisfy this requirement, it is necessary to identify and control all these manufacturing defects and anomalies that influence the durability of the bonded joint. In this experimental research, a methodology has been developed to control possible manufacturing defects including porosity, unbonded area, and adhesive thickness and flatness variation of bond area. To evaluate the developed methodology, static and fatigue tests were conducted and uncertainty in the fatigue life was analysed. It was found that these in-situ undetectable defects and anomalies have significant direct influence on the fatigue life and fatigue life uncertainty of bonded joints relative to their static strength. An adaptation of this methodology using paste adhesive and high precision measuring and restraining tool during manufacturing stage can be used to create an ideal scarf joint for fatigue studies.
Akbar Khatibi is an Associate professor at the School of Engineering (Aerospace Engineering & Aviation), RMIT University. His primary areas of teaching and research are structures, advanced composite materials, fracture mechanics and fatigue analysis of aerospace structures. Akbar joined RMIT University in 2011, and his professional experience includes working as the program manager for Master of Airworthiness and HDR manager of the discipline. In his academic research, he was involved as a chief investigator in several competitive research grants including those from ARC Discovery and Linkage schemes as well as ONR-USA.