Composite Materials

COMPOSITE MATERIALS AND TECHNOLOGY

(IN AEROSPACE AND HELICOPTER INDUSTRY) SUBMITTED BY:RAHUL RANJAN ROLL NO:- 13 I & P Engg. FINAL YEAR

INTRODUCTION  fibreglass was first modern composite and it finds use in boat hulls, surfboards, sporting goods, car bodies etc.  composite materials have strength and stiffness combined with lightness.  Products with properties that exactly fit the requirement for a particular structure for a particular purpose.

Continued…  Modern aviation, both military & civil, would be much less efficient without composites.  The industry demands for materials that are both light & strong.  The airframes of some smaller aircraft are made entirely from composites, as are the wing, tail & body panels of large commercial aircraft.  Propellers and rotor blades can also be made using composites.

Composite Materials & Technology composite materials are particularly attractive aviation and aerospace applications because of their exceptional strength and stiffness- to density ratios and superior physical properties.

FIBROUS COMPOSITES  Consists of relatively strong, stiff fibres in a tough resin matrix.  Carbon and Glass fibre reinforced plastic are used in aerospace.  By combining materials with complementary properties, a composite material with most or all of the benefits can be obtained with few or none of the weakness of individual components.

PARTICULATE COMPOSITES  Metal matrix composites are non- metallic particles in a metallic matrix, for instance silicon carbide particles combined with aluminium alloy.  These are currently being developed for aviation and aerospace industry.

DIFFERENCES  Particulate composites are Isotropic but Fibrous composites are Anisotropic.  Anisotropy is overcome by stacking layers having thickness less than 1mm one over other with fibres oriented at different angles to form a laminate.  Differently oriented layers are stacked in a specific sequence to tailor the properties of the laminate to withstand loads

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COMPLEX SHAPES

Composites can be formed into more complex shapes. This reduces no. of parts making a given component. Reduces need for fasteners and joints giving uniform strength and shorter assembly time.

FABRICATION TIME The individual layers which are pre-impregnated with the resin matrix are cut to required shapes and stacked in the specified sequence over former. This assembly is then subjected to a sequence of temperatures and pressure to cure the material. The product is then checked thoroughly.

The following are some of the military and commercial aircraft that use significant amounts of composites in the airframe. Fighter aircraft U.S- AV-8B, F14, F18, YF23, F16, F22, JSF, UCAV Europe-Harrier GR7, Gripen JAS39,Mirage2000, Rafael, Euro fighter, Lavi,EADS- Mako Russia-MIG29, Su series Bomber-B2 Transport U.S-KC135, C17 777, 767, MD11 Europe-A320, A340 A380, Tu204, ATR42, Falcon900, A300-600 General Aviation- Piaggio, Starship, Premier1, Cirrus SR20&SR22 Rotary Aircraft- V22, Eurocopter Comanche, RAH66, BA609, EH101, Superlynx300, S92

ADVANCED COMPOSITES AND HELICOPTERS Advanced composites consist of thin sheets of plastic which are embedded with very fine fibres for strengthening. The sheet is very stiff and strong in fibre direction and has lower weight. Many sheets are bonded together to form a laminate. By bonding sheets together in different orientation, a laminate with required strength and stiffnesses can be created.

EVOLUTION OF COMPOSITES IN HELICOPTER 1930s & 40s – wood and fabric structures. 1950s & 60s – thin skinned adhesively bonded aluminium structures. 1970s – fibreglass technology. 1980s – fuselage sections and very large components were being manufactured from carbon, aramid, or fibreglass composites. The most important contribution towards improving helicopter performance was by making the airframe lighter and smaller.

ADVANCED COMPOSITES 101 Structures made from metals have inherent strength in directions it may not need. By predicting the type and magnitude of load a part will handle, we can design strength only in required direction and eliminate where useless.

Continued… composite materials have specific properties like: Fibreglass:- high strength to wt. ratio, good environmental resistance, flexibility. Carbon fibre:- higher modulus, lighter, high stiffness. Aramid:- extremely tough, durable, high tensile strength, light wt.

COMPOSITE REPAIRS Aramid wicks up moisture or any other liquid it is exposed to. water intrusion lowers the strength. Elevated temperature cure can cause the skin to blow off. Two or more types of fibres can be used in a laminate to get unique combination of properties. An example is carbon fibre coated with kevlar. As carbon is brittle, it is protected by the layer of kevlar and load is carried mainly by carbon fibre.

BENEFITS OF COMPOSITES Cost : prototypes, Mass production, Durability, production time. Weight : light wt, uniform wt distribution. Strength & stiffness : high value, directional property. Dimensions : large parts, special geometry. Surface properties : corrosion resistant, weather resistant, tailored surface finish. Thermal properties : low thermal conductivity, low coeff. of thermal expansion. Electric properties : non-magnetic, radar transparency, high dielectric strength.

DISADVANTAGES Expensive raw materials. Higher fabrication cost. Susceptibility to moisture.