Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Applied Composite Materials: An International Journal for the Science and Application of Composite Materials (v.10, #4-5)
An Historic Overview of the Development of Fibre Metal Laminates by C. A. J. R. Vermeeren (pp. 189-205).
In this paper a brief overview of the history of Fibre Metal Laminates Arall and Glare is given as background information for the other, technical articles in this journal. The story of the development of Fibre Metal Laminates is rather a unique story in the history of aircraft materials: A university laboratory invented, developed and certified an aircraft material. Many parties were involved naturally, yet the very heart of the activity was the Structures and Materials Laboratory of the Faculty of Aerospace Engineering of Delft University of Technology in The Netherlands. At the break of the world's largest passenger transport aircraft, the Airbus A380, in which a substantial part of the fuselage will be made of Glare, the glass fibre-aluminium version of Fibre Metal Laminates, it is a good moment to tell some of its history.
Keywords: Fibre Metal Laminates; Arall; Glare; residual strength; burn through; static properties; Delft University; Structural Laminates Company; Akzo; Alcoa; Fokker; 3M; ballistic material; barrel test
Static Properties of Fibre Metal Laminates by M. Hagenbeek; C. van Hengel; O. J. Bosker; C. A. J. R. Vermeeren (pp. 207-222).
In this article a brief overview of the static properties of Fibre Metal Laminates is given. Starting with the stress-strain relation, an effective calculation tool for uniaxial stress-strain curves is given. The method is valid for all Glare types. The Norris failure model is described in combination with a Metal Volume Fraction approach leading to a useful tool to predict allowable blunt notch strength. The Volume Fraction approach is also useful in the case of the shear yield strength of Fibre Metal Laminates. With the use of the Iosipescu test shear yield properties are measured.
Keywords: Fibre Metal Laminates; Glare; stress-strain relation; static properties; shear-yield strength; blunt notch strength; Iosipescu test
Fatigue and Damage Tolerance of Glare by R. C. Alderliesten; M. Hagenbeek; J. J. Homan; P. A. Hooijmeijer; T. J. de Vries; C. A. J. R. Vermeeren (pp. 223-242).
Methods have been developed to describe the fatigue initiation and propagation mechanisms in flat panels as well as mechanically fastened joints and to determine the residual strength of large flat panels. Glare shows excellent crack growth characteristics due to the mechanism of delamination and fibre bridging. The fatigue insensitive fibres restrain the crack opening and transfer load over the crack in the metal layers. During the initiation phase fibre bridging does not occur and the behaviour is dominated by the metal initiation properties. Mechanically fastened joints introduce additional effects such as secondary bending, load transfer and aspects related to the fastener installation. The residual strength of Glare is dependent on the amount of broken fibres and the delamination size and can be described with the R-curve approach.The impact resistance of Glare is related to the aluminium and glass/epoxy properties and is significantly higher than the impact resistance of monolithic aluminium. The same has been proven for fire resistance. Depending on the Glare grade and thickness, the outer aluminium layer will melt away, whereas the other layers will remain intact due to carbonisation of the glass/epoxy layers and delamination of the laminate. The air in the delaminations will act as insulation, keeping the temperatures at the non-exposed side relatively low.
Keywords: fatigue; Fibre Metal Laminates; Glare; impact; joints; burn-through; lightning strike
Long Term Behaviour of Glare by B. Borgonje; M. S. Ypma (pp. 243-255).
Aircraft are operated in a wide variety of environments, for periods of up to 30 years. In order to maintain safe and economical travel, it is necessary to have good knowledge of the long-term behaviour of the materials that an aircraft are built of. Over longer periods of time, one of the main threats to materials is the influence of the environment, especially that of moisture combined with temperature. The combination of materials used in Glare complicates the long-term behaviour. By investigating environmental influences on each of the different components of Glare, a basic understanding of the effects on the laminate as a whole can be obtained. In most cases, the laminated build-up has a positive effect on the environmental durability of Glare, but care needs to be taken in areas of combined moisture absorption, stress concentrations and elevated temperature.
Keywords: corrosion; durability; environmental effects; Glare
Glare Design Aspects and Philosophies by C. A. J. R. Vermeeren; Th. Beumler; J. L. C. G. de Kanter; O. C. van der Jagt; B. C. L. Out (pp. 257-276).
The very nature of Glare is its crack bridging mechanism, which provides superior damage tolerance properties. Depending on the property, Glare shows either monolithic metal or composite behaviour, which challenges the definition of strength justification and certification procedures. Airworthiness regulations have to be interpreted for Glare in order to guarantee the same level of safety as obtained for aircraft structures made of other materials and to take at the same time benefit of its particular properties.Cut-outs are highly fatigue sensitive due to the stress concentrations they cause. In aircraft fuselages these cut-outs are quite large in the case of the windows and doors. The stress level may be increased through the application of Glare in the doubler packages, due to the improved fatigue behaviour compared to conventional aluminium. Glare also presents the possibility of tailoring the material to the load, i.e. fibres aligned with the load, e.g., a 45 degree orientation. FE analysis defined the total doubler package and a test programme was run to confirm the behaviour of the material and to predict the crack behaviour of the Glare door corner.Some aspects of the detailed design of aircraft structures in Glare, the design of splices and riveted joints are discussed. In order to apply Glare in very large fuselage panels, a splice concept was developed, which allows a number of longitudinal splices to be cured in the same curing cycle as the basic material. Through the introduction of this splicing concept, the width of a panel is no longer limited to the maximum width of the aluminium sheet. Internal local reinforcements (doublers) can be integrated into the panel during lay-up. A discussion on the design of riveted joints in Glare is held.
Keywords: Glare; Fibre Metal Laminate; damage tolerance; accidental damage; impact; cut-out; aircraft door; Glare splice concept; splice design; Glare doubler; riveted joints; lap joint; detailed design
Some Inspection Methods for Quality Control and In-service Inspection of GLARE by J. Sinke (pp. 277-291).
Quality control of materials and structures is an important issue, also for GLARE. During the manufacturing stage the processes and materials should be monitored and checked frequently in order to obtain a qualified product. During the operation of the aircraft, frequent monitoring and inspections are performed to maintain the quality at a prescribed level. Therefore, in-service inspection methods are applied, and when necessary repair activities are conducted. For the quality control of the GLARE panels and components during manufacturing, the C-scan method proves to be an effective tool. For in-service inspection the Eddy Current Method is one of the suitable options. In this paper a brief overview is presented of both methods and their application on GLARE products.
Keywords: C-scan; manufacturing; reference and witness panels; Eddy Current Method; sliding and pencil probes; riveted joints
Manufacturing of GLARE Parts and Structures by J. Sinke (pp. 293-305).
GLARE is a hybrid material consisting of alternating layers of metal sheets and composite layers, requiring special attention when manufacturing of parts and structures is concerned. On one hand the applicable manufacturing processes for GLARE are limited, on the other hand, due to the constituents and composition of the laminate, it offers new opportunities for production. One of the opportunities is the manufacture of very large skin panels by lay-up techniques. Lay-up techniques are common for full composites, but uncommon for metallic structures. Nevertheless, large GLARE skin panels are made by lay-up processes. In addition, the sequences of forming and laminating processes, that can be selected, offer manufacturing options that are not applicable to metals or full composites. With respect to conventional manufacturing processes, the possibilities for Fibre Metal Laminates in general, are limited. The limits are partly due to the different failure modes, partly due to the properties of the constituents in the laminate. For machining processes: the wear of the cutting tools during machining operations of GLARE stems from the abrasive nature of the glass fibres. For the forming processes: the limited formability, expressed by a small failure strain, is related to the glass fibres. However, although these manufacturing issues may restrict the use of manufacturing processes for FMLs, application of these laminates in aircraft is not hindered.
Keywords: assembly; bolted joint; Fibre Metal Laminates; formability; GLARE; lay-up technology; machining; riveted joint; splicing
Maintenance of Glare Structures and Glare as Riveted or Bonded Repair Material by H. J. M. Woerden; J. Sinke; P. A. Hooijmeijer (pp. 307-329).
Aircraft structures constructed from new and advanced materials will become more common in the near future, starting with the use of the Fibre Metal Laminate Glare in large parts of the Airbus A-380 fuselage. These materials are primarily used because of their excellent damage tolerance properties. However, questions about maintenance and repair of such structures need to be answered before such new materials can be used. These questions include whether new and advanced materials can be repaired in a conventional way, which would not only be preferable from the operator's point of view (no change in tools, maintenance procedures, and personnel training), but also from the manufacturer's point of view (Structural Repair Manuals similar to aluminium structures). A Glare demonstrator panel has been designed and applied to an Airbus A-310 and research into the repairability of Glare has been performed to answer these questions. Apart from looking into the repairability of Glare structures, the material itself is also investigated as material for bonded repair patches. Bonded repair many times proves to be a more viable solution than conventional riveted repair due to its more efficient load transfer. Important aspects of bonded (Glare) repair are under investigation to show that bonded patch repair is not only working for the ageing aircraft of several Air Forces around the world, but is also a promising candidate for safe and cost-effective repairs to ageing and new (incidental damage) aircraft of commercial operators. This research is conducted cooperatively by Delft University of Technology and the United States Air Force Academy and has led to two real-life repairs on a C-5A “Galaxy”.
Keywords: repair; Glare; riveted; bonded; fatigue; inspection; maintenance