08-16-2017, 08:43 PM
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1.INTRODUCTION
1.1 What are Aluminum Alloys ?
Aluminum is a revolutionary metal. It changed the scenario in engineering designing for almost everything ranging from utensils to aircrafts. It was also referred to as the gold in its early days of discovery. Aluminum exhibits outstanding strength with low density and light weight. As the engineering marvels developed an increasing demand was witnessed to further reduce the weight of aluminum and to increase its strength for applications like ship building, aircraft designing, etc. this was achieved through the development of alloys i.e. developing new materials by adding a percentage of other metals into the metal whose properties are to be altered. This technique became popular amongst engineers and they started using alloys wherever it was possible. Aluminum alloys played a very crucial role in designing aircrafts, automobiles, ships etc.
1.2 What are Honeycomb Cores ?
Honeycomb cores are available in a variety of materials for sandwich structures. These range from paper and card for low strength and stiffness, low load applications (such as domestic internal doors) to high strength and stiffness, extremely lightweight components for aircraft structures. Honeycombs can be processed into both flat and curved composite structures, and can be made to conform to compound curves without excessive mechanical force or heating.
Properties of honeycomb materials depend on the size (and therefore frequency) of the cells and the thickness and strength of the web material. Sheets can range from typically 3-50 mm in thickness and panel dimensions are typically 1200 x 2400mm, although it is possible to produce sheets up to 3m x 3m.
Honeycomb cores can give stiff and very light laminates but due to their very small bonding area they are almost exclusively used with high-performance resin systems such as epoxies so that the necessary adhesion to the laminate skins can be achieved.
Sandwich construction is an attractive structural design concept, as by the proper choice of materials and geometry, constructions having high ratios of stiffness-to-weight can be achieved. The sandwich panel is the composition of a weak core material with strong and stiff faces bonded on the upper and lower sides. The facings provide practically all of the overall bending and in-plane extensional rigidity to the sandwich. Sandwich construction is commonly used in structures where strength, stiffness,and weight efficiency are required. Low-density, hexagonal honeycombs are preferred as the core material on a performance basis. Honeycomb materials have been extensively used as energy absorbers to resist external loads due to their high energy absorption capacity
1.3 What is Aluminum Honeycomb ?
Aluminium honeycomb produces one of the highest strength/weight ratios of any structural material. There are various configurations of the adhesive bonding of the aluminium foil which can lead to a variety of geometric cell shapes (usually hexagonal). Properties can also be controlled by varying the foil thickness and cell size. The honeycomb is usually supplied in the unexpanded block form and is stretched out into a sheet on-site.
Despite its good mechanical properties and relatively low price, aluminium honeycomb has to be used with caution in some applications, such as large marine structures, because of the potential corrosion problems in a salt-water environment. In this situation care also has to be exercised to ensure that the honeycomb does not come into direct contact with carbon skins since the conductivity can aggravate galvanic corrosion. Aluminium honeycomb also has the problem that it has no 'mechanical memory'. On impact of a cored laminate, the honeycomb will deform irreversibly whereas the FRP skins, being resilient, will move back to their original position. This can result in an area with an unbonded skin with much reduced mechanical properties.
This report lists the materials, configurations, and mechanical properties of Hexcel s standard honeycomb as a guide to selecting honeycomb core best suited for particular applications
1.INTRODUCTION
1.1 What are Aluminum Alloys ?
Aluminum is a revolutionary metal. It changed the scenario in engineering designing for almost everything ranging from utensils to aircrafts. It was also referred to as the gold in its early days of discovery. Aluminum exhibits outstanding strength with low density and light weight. As the engineering marvels developed an increasing demand was witnessed to further reduce the weight of aluminum and to increase its strength for applications like ship building, aircraft designing, etc. this was achieved through the development of alloys i.e. developing new materials by adding a percentage of other metals into the metal whose properties are to be altered. This technique became popular amongst engineers and they started using alloys wherever it was possible. Aluminum alloys played a very crucial role in designing aircrafts, automobiles, ships etc.
1.2 What are Honeycomb Cores ?
Honeycomb cores are available in a variety of materials for sandwich structures. These range from paper and card for low strength and stiffness, low load applications (such as domestic internal doors) to high strength and stiffness, extremely lightweight components for aircraft structures. Honeycombs can be processed into both flat and curved composite structures, and can be made to conform to compound curves without excessive mechanical force or heating.
Properties of honeycomb materials depend on the size (and therefore frequency) of the cells and the thickness and strength of the web material. Sheets can range from typically 3-50 mm in thickness and panel dimensions are typically 1200 x 2400mm, although it is possible to produce sheets up to 3m x 3m.
Honeycomb cores can give stiff and very light laminates but due to their very small bonding area they are almost exclusively used with high-performance resin systems such as epoxies so that the necessary adhesion to the laminate skins can be achieved.
Sandwich construction is an attractive structural design concept, as by the proper choice of materials and geometry, constructions having high ratios of stiffness-to-weight can be achieved. The sandwich panel is the composition of a weak core material with strong and stiff faces bonded on the upper and lower sides. The facings provide practically all of the overall bending and in-plane extensional rigidity to the sandwich. Sandwich construction is commonly used in structures where strength, stiffness,and weight efficiency are required. Low-density, hexagonal honeycombs are preferred as the core material on a performance basis. Honeycomb materials have been extensively used as energy absorbers to resist external loads due to their high energy absorption capacity
1.3 What is Aluminum Honeycomb ?
Aluminium honeycomb produces one of the highest strength/weight ratios of any structural material. There are various configurations of the adhesive bonding of the aluminium foil which can lead to a variety of geometric cell shapes (usually hexagonal). Properties can also be controlled by varying the foil thickness and cell size. The honeycomb is usually supplied in the unexpanded block form and is stretched out into a sheet on-site.
Despite its good mechanical properties and relatively low price, aluminium honeycomb has to be used with caution in some applications, such as large marine structures, because of the potential corrosion problems in a salt-water environment. In this situation care also has to be exercised to ensure that the honeycomb does not come into direct contact with carbon skins since the conductivity can aggravate galvanic corrosion. Aluminium honeycomb also has the problem that it has no 'mechanical memory'. On impact of a cored laminate, the honeycomb will deform irreversibly whereas the FRP skins, being resilient, will move back to their original position. This can result in an area with an unbonded skin with much reduced mechanical properties.
This report lists the materials, configurations, and mechanical properties of Hexcel s standard honeycomb as a guide to selecting honeycomb core best suited for particular applications