Composites - Lecture 1 - Material Engineering, Lecture notes of Material Engineering

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Composites

Composite technology with T800 Carbon Fiber^1

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 Composites types are designated by:

 the matrix material (Ceramic Matrix Composite, Metal MC, Polymer MC)

 the reinforcement (particles, fibers, structural)

 Composite property benefits:

 MMC: improved E , y, creep performance, Tensile Strength

 CMC: improved KIc

 PMC: improved E , 

y , TS,^ creep resistance

 Particulate-reinforced:

 Types: large-particle and dispersion-strengthened

 Properties are isotropic

 Fiber-reinforced:

 Types: continuous (aligned) and discontinuous (aligned or random)

 Properties can be isotropic or anisotropic

 Structural:

 Laminates and sandwich panels

Overview

4 Composite  (^) A composite material is basically a combination of two or more materials that are mechanically bonded together.  (^) The resulting material has characteristics that are different than the components in isolation.  (^) The concept of composite materials is ancient. An example is adding straw to mud for building stronger mud walls. Most commonly, composite materials have a bulk phase or matrix and a dispersed, non-continuous, phase called the reinforcement.  (^) Some other examples of basic composites include concrete (cement mixed with sand and aggregate), reinforced concrete (steel rebar in concrete), and fiberglass (glass strands in a resin matrix).

Older Technology

Why use composites? 7

Boeing 787 – All Composite Fuselage

 The Boeing 787 “Dreamliner” is a mid-sized, wide-body, twin-engine jet airliner still being tested.

 Rationale for the new design: more fuel-efficient than predecessors and the first major airliner to use

composite materials for most of its construction. The 787 has involved a large-scale “collaboration”

with numerous suppliers.

 The 787's has an all-composite fuselage (main body). The Boeing 777 contains 50% aluminum and

12% composites, the new airplane uses 50% composite (mostly carbon fiber reinforced plastic), 15%

aluminum, and other materials.

 The 787 fuselage is made up of composite barrel sections joined end to end. Each fuselage barrel will

be manufactured in one piece. This will eliminate the need for some 50,000 fasteners used in

conventional airplane assembly.

 It was stated that carbon fiber, unlike metal, does not visibly show cracks and fatigue. Boeing has

dismissed such notions, insisting that composites have been used on wings and other passenger

aircraft parts for many years and they have not been an issue.

 The 787 features lighter-weight construction. Its materials (by weight) are: 50% composite, 20%

aluminum, 15% titanium, 10% steel, 5% other. The 787 will be 80% composite by volume. Each 787

contains approximately 35 tons of carbon fiber reinforced plastic, made with 23 tons of carbon fiber.

 Composites are used on fuselage, wings, tail, doors and interior.

 Aluminum is used on wing and tail leading edges, titanium used mainly on engines with steel used in

various places.

CFRP

 Carbon fiber-reinforced polymer or carbon fiber-reinforced plastic

( CFRP or CRP ), is a very strong, light and expensive composite material

or fiber-reinforced polymer. Similar to fiberglass (glass reinforced

polymer), the composite material is commonly referred to by the name of

its reinforcing fibers (carbon fiber). The polymer is most often epoxy, but

other polymers, such as polyester, vinyl ester or nylon can be used.

 Some composites contain both carbon fiber and other fibers such as

kevlar, aluminum and fiberglass reinforcement.

 It has many applications in aerospace and automotive fields, as well as

in sailboats, and notably in modern bicycles and motorcycles.

 CFRP’s has a higher strength-to-weight ratio than traditional aircraft

materials, and helped make the Boeing 787 a lighter aircraft.

 Improved manufacturing techniques are reducing the costs and time to

manufacture, making it increasingly common in small consumer goods

as well, such as laptops, tripods, fishing rods, paintball equipment,

archery equipment, racquet frames, stringed instrument bodies, classical

guitar strings, drum shells, golf clubs and pool/billiards/snooker cues.

Shortcomings  (^) Despite their strength and low weight, composites have not been a miracle solution for aircraft structures. Composites are hard to inspect for flaws. Some of them absorb moisture. Most importantly, they can be expensive, primarily because they are labor intensive and often require complex and expensive fabrication machines.  (^) Aluminum, by contrast, is easy to manufacture and repair. Anyone who has ever gotten into a minor car accident has learned that dented metal can be hammered back into shape, but a crunched fiberglass bumper has to be completely replaced. The same is true for many composite materials used in aviation. 11