Materials and Design 56(2014)862-871 Contents lists available at ScienceDirect Materials Materials and Design Design ELSEVIER journal homepage:www.elsevier.com/locate/matdes Review Recent developments in advanced aircraft aluminium alloys CrossMark Tolga Dursun a.*,Costas Soutisb Aselsan Inc,Ankara 06750,Turkey bAerospace Research Institute,University of Manchester,Manchester M13 9PL,UK ARTICLE INFO ABSTRACT Article history: Aluminium alloys have been the primary material for the structural parts of aircraft for more than Received 16 September 2013 80 years because of their well known performance,well established design methods,manufacturing Accepted 2 December 2013 and reliable inspection techniques.Nearly for a decade composites have started to be used more widely Available online 13 December 2013 in large commercial jet airliners for the fuselage,wing as well as other structural components in place of aluminium alloys due their high specific properties,reduced weight,fatigue performance and corrosion Keywords: resistance.Although the increased use of composite materials reduced the role of aluminium up to some Aircraft structures extent,high strength aluminium alloys remain important in airframe construction.Aluminium is a rela- Aluminium alloys Al-Li alloys tively low cost,light weight metal that can be heat treated and loaded to relatively high level of stresses, Composites and it is one of the most easily produced of the high performance materials,which results in lower man- Mechanical properties ufacturing and maintenance costs.There have been important recent advances in aluminium aircraft alloys that can effectively compete with modern composite materials.This study covers latest develop- ments in enhanced mechanical properties of aluminium alloys,and high performance joining techniques The mechanical properties on newly developed 2000,7000 series aluminium alloys and new generation Al-Li alloys are compared with the traditional aluminium alloys.The advantages and disadvantages of the joining methods,laser beam welding and friction stir welding,are also discussed. 2013 Elsevier Ltd.All rights reserved. 1.Introduction increasing tensile strength,elastic modulus or damage tolerance 1].Airframe durability is another parameter that directly affects The cost reduction for aircraft purchase and operation has be- costs.The cost of service and maintenance over the 30-year life come a driving force in many airline companies.Cost reduction of the aircraft are estimated to exceed the original purchase price can be achieved by decreasing the fuel consumption,maintenance by a factor of two[1.Therefore,both material producers and air- cost,operational costs,frequency of periodical controls and craft designers are working in harmony to reduce weight,improve increasing the service life and carrying more passengers at a time. damage tolerance,fatigue and corrosion resistance of the new Therefore aircraft manufacturers are competing to meet the metallic alloys.As a result,near future primary aircraft structures requirements of their airline customers.Weight reduction can im- will show an extended service life and require reduced frequency prove fuel consumption,increase payload and increase range. of inspections. Additionally,improved and optimised mechanical properties of Composite materials are increasingly being used in aircraft pri- the materials can result in increased period between maintenance mary structures (B787,Airbus A380,F35,and Typhoon).Fig.1 and reduce repair costs.Since the material has a great impact on shows the increased usage of composites in several types of Boeing cost reduction,airframe manufacturers and material producers fo- aircraft.The attractiveness of composites in the manufacturing of cus on the development of new materials to meet customer high performance structures relies on their superior mechanical requirements.Hence,a current challenge is to develop materials properties when compared to metals.such as higher specific stiff- that can be used in fuselage and wing construction with improve- ness,specific strength (normalised by density),fatigue and corro- ments in both structural performance and life cycle cost.According sion resistance.Although composites are thought to be the to the design trials it is seen that an effective way of reducing the preferable material for wing and fuselage structures,their higher aircraft weight is by reducing the material density.It is found that certification and production costs,relatively low resistance to im- the decrease in density is about 3-5 times more effective than pact and complicated mechanical behaviour due to change in envi- ronmental conditions (moisture absorption.getting soft/brittle when exposed to hot/cold environments)make designers to ex- Correspondng author.Tel.:+90 312 847 53 00. plore alternative material systems.Fibre metal laminates such as E-mail addresses:tdursun@aselsan.com.tr (T.Dursun).constantinos.soutis@ manchester.ac.uk (C.Soutis). GLARE which combines aluminium layers with glass fibre epoxy 0261-3069/$-see front matter 2013 Elsevier Ltd.All rights reserved. http://dx.doi.org/10.1016/j.matdes.2013.12.002Review Recent developments in advanced aircraft aluminium alloys Tolga Dursun a,⇑ , Costas Soutis b a Aselsan Inc, Ankara 06750, Turkey b Aerospace Research Institute, University of Manchester, Manchester M13 9PL, UK article info Article history: Received 16 September 2013 Accepted 2 December 2013 Available online 13 December 2013 Keywords: Aircraft structures Aluminium alloys Al–Li alloys Composites Mechanical properties abstract Aluminium alloys have been the primary material for the structural parts of aircraft for more than 80 years because of their well known performance, well established design methods, manufacturing and reliable inspection techniques. Nearly for a decade composites have started to be used more widely in large commercial jet airliners for the fuselage, wing as well as other structural components in place of aluminium alloys due their high specific properties, reduced weight, fatigue performance and corrosion resistance. Although the increased use of composite materials reduced the role of aluminium up to some extent, high strength aluminium alloys remain important in airframe construction. Aluminium is a rela￾tively low cost, light weight metal that can be heat treated and loaded to relatively high level of stresses, and it is one of the most easily produced of the high performance materials, which results in lower man￾ufacturing and maintenance costs. There have been important recent advances in aluminium aircraft alloys that can effectively compete with modern composite materials. This study covers latest develop￾ments in enhanced mechanical properties of aluminium alloys, and high performance joining techniques. The mechanical properties on newly developed 2000, 7000 series aluminium alloys and new generation Al–Li alloys are compared with the traditional aluminium alloys. The advantages and disadvantages of the joining methods, laser beam welding and friction stir welding, are also discussed. 2013 Elsevier Ltd. All rights reserved. 1. Introduction The cost reduction for aircraft purchase and operation has be￾come a driving force in many airline companies. Cost reduction can be achieved by decreasing the fuel consumption, maintenance cost, operational costs, frequency of periodical controls and increasing the service life and carrying more passengers at a time. Therefore aircraft manufacturers are competing to meet the requirements of their airline customers. Weight reduction can im￾prove fuel consumption, increase payload and increase range. Additionally, improved and optimised mechanical properties of the materials can result in increased period between maintenance and reduce repair costs. Since the material has a great impact on cost reduction, airframe manufacturers and material producers fo￾cus on the development of new materials to meet customer requirements. Hence, a current challenge is to develop materials that can be used in fuselage and wing construction with improve￾ments in both structural performance and life cycle cost. According to the design trials it is seen that an effective way of reducing the aircraft weight is by reducing the material density. It is found that the decrease in density is about 3–5 times more effective than increasing tensile strength, elastic modulus or damage tolerance [1]. Airframe durability is another parameter that directly affects costs. The cost of service and maintenance over the 30-year life of the aircraft are estimated to exceed the original purchase price by a factor of two [1]. Therefore, both material producers and air￾craft designers are working in harmony to reduce weight, improve damage tolerance, fatigue and corrosion resistance of the new metallic alloys. As a result, near future primary aircraft structures will show an extended service life and require reduced frequency of inspections. Composite materials are increasingly being used in aircraft pri￾mary structures (B787, Airbus A380, F35, and Typhoon). Fig. 1 shows the increased usage of composites in several types of Boeing aircraft. The attractiveness of composites in the manufacturing of high performance structures relies on their superior mechanical properties when compared to metals, such as higher specific stiff￾ness, specific strength (normalised by density), fatigue and corro￾sion resistance. Although composites are thought to be the preferable material for wing and fuselage structures, their higher certification and production costs, relatively low resistance to im￾pact and complicated mechanical behaviour due to change in envi￾ronmental conditions (moisture absorption, getting soft/brittle when exposed to hot/cold environments) make designers to ex￾plore alternative material systems. Fibre metal laminates such as GLARE which combines aluminium layers with glass fibre epoxy 0261-3069/$ - see front matter 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.matdes.2013.12.002 ⇑ Correspondng author. Tel.: +90 312 847 53 00. E-mail addresses: tdursun@aselsan.com.tr (T. Dursun), constantinos.soutis@ manchester.ac.uk (C. Soutis). Materials and Design 56 (2014) 862–871 Contents lists available at ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes