Ramkaran ppt

Introduction To Composite Materials

Ramkaran yadav

Introduction to Composites1. What is the matrix in a composite and what materials are commonly

used as a matrix?

2. What is reinforcement in composites ?

3. Be able to decide different factors responsible for properties of composite.

4. Know the equation for the critical length (Lc) of a fiber..

Composites in Action

http://www.sr-71.org/photogallery/blackbird/

Composite Material

Two inherently different materials that when combined together produce a material with properties that exceed

the constituent materials.

Fiber Reinforced Polymer Matrix Matrix • Transfer Load to

Reinforcement• Temperature Resistance• Chemical Resistance

Reinforcement

• Tensile Properties• Stiffness• Impact Resistance

Matrix Considerations

End Use TemperatureToughnessCosmetic IssuesFlame RetardantProcessing MethodAdhesion Requirements

Matrix Materials Functions of the matrix

– Transmit force between fibers– arrest cracks from spreading between fibers

do not carry most of the load– hold fibers in proper orientation– protect fibers from environment

mechanical forces can cause cracks that allow environment to affect fibers

Demands on matrix – Interlaminar shear strength– Toughness– Moisture/environmental resistance– Temperature properties– Cost

Types of Composite Materials

There are five basic types of composite materials: Fiber, particle, flake, laminar or layered and filled composites.

A. Fiber CompositesIn fiber composites, the fibers reinforce along the line of their length. Reinforcement may be mainly 1-D, 2-D or 3-D. Figure shows the three basic types of fiber orientation.

1-D gives maximum strength in one direction.

2-D gives strength in two directions.

Isotropic gives strength equally in all directions.

B. Particle Composites Particles usually reinforce a composite equally in all directions (called

isotropic). Plastics, cermets and metals are examples of particles. Particles used to strengthen a matrix do not do so in the same way as

fibers. For one thing, particles are not directional like fibers. Spread at random through out a matrix, particles tend to reinforce in all directions equally.

Cermets (1) Oxide–Based cermets(e.g. Combination of Al2O3 with Cr) (2) Carbide–Based Cermets(e.g. Tungsten–carbide, titanium–carbide) Metal–plastic particle composites(e.g. Aluminum, iron & steel, copper particles) Metal–in–metal Particle Composites and Dispersion

Hardened Alloys(e.g. Ceramic–oxide particles)

C. Laminar Composites - 1 Laminar composites involve two or more layers of

the same or different materials. The layers can be arranged in different directions to give strength where needed. Speedboat hulls are among the very many products of this kind.

D. Combined Composites It is possible to combine several

different materials into a single composite. It is also possible to combine several different composites into a single product. A good example is a modern ski. (combination of wood as natural fiber, and layers as laminar composites)

E. Filled Composites There are two types of filled composites. In one,

filler materials are added to a normal composite result in strengthening the composite and reducing weight. The second type of filled composite consists of a skeletal 3-D matrix holding a second material. The most widely used composites of this kind are sandwich structures and honeycombs.

Types of CompositesMatrix phase/Reinforcement Phase

Metal Ceramic Polymer

Metal Powder metallurgy parts – combining immiscible metals

Cermets (ceramic-metal composite)

Brake pads

Ceramic Cermets, TiC, TiCNCemented carbides – used in toolsFiber-reinforced metals

SiC reinforced Al2O3 Tool materials

Fiberglass

Polymer Kevlar fibers in an epoxy matrix

Elemental (Carbon, Boron, etc.)

Fiber reinforced metalsAuto partsaerospace

Rubber with carbon (tires)Boron, Carbon reinforced plastics

MMC’s CMC’s PMC’sMetal Matrix Composites Ceramic Matrix Comp’s. Polymer Matrix Comp’s

Mechanical Engineering Dept. 15Ken Youssefi

Composites – Metal MatrixThe metal matrix composites offer higher modulus of elasticity, ductility, and resistance to elevated temperature than polymer matrix composites. But, they are heavier and more difficult to process.

Design Objective

Performance: Strength, Temperature, StiffnessManufacturing TechniquesLife Cycle ConsiderationsCost

Matrix Types

EpoxyEpoxies have improved strength and stiffness properties

over polyesters. Epoxies offer excellent corrosion resistance and resistance to solvents and alkalis. Cure cycles are usually longer than polyesters, however no

by-products are produced.

Flexibility and improved performance is also achieved by the utilization of additives and fillers.

Reinforcement

Fiber TypeFiberglassCarbonAramid

Textile StructureUnidirectionalWovenBraid

Carbon Fiber

PAN: Fiber made from Polyacrylonitrile precursor fiber

High strength and stiffnessLarge variety of fiber types available

Standard Modulus Intermediate Modulus Density 1.79 g/cc 1.79 g/ccTensile Strength 600 ksi 800 ksiTensile Modulus 33 Msi 42 MsiElongation 1.8 % 1.8 %

Mechanical Engineering Dept. 20

Composites – Ceramic Matrix

Ceramic matrix composites (CMC) are used in applications where resistance to high temperature and corrosive environment is desired. CMCs are strong and stiff but they lack toughness (ductility)

Matrix materials are usually silicon carbide, silicon nitride and aluminum oxide, and mullite (compound of aluminum, silicon and oxygen). They retain their strength up to 3000 oF.

Fiber materials used commonly are carbon and aluminum oxide.

Applications are in jet and automobile engines, deep-see mining, cutting tools, dies and pressure vessels.


Application of Composites

Pedestrian bridge in Denmark, 130 feet

long (1997)

Swedish Navy, Stealth (2005)

Lance Armstrong’s 2-lb. Trek bike, 2004 Tour de France


Application of Composites in Aircraft Industry

20% more fuel efficiency and 35,000 lbs. lighter

23

Advantages of Composites

Composites have a higher specific strength than many other materials. A distinct advantage of composites over other materials is the ability to use many combinations of resins and reinforcements, and therefore custom tailor the mechanical and physical properties of a structure.

Higher Specific Strength (strength-to-weight ratio)

The lowest properties for each material are associated with simple manufacturing processes and material forms (e.g. spray lay-up glass fibre), and the higher properties are associated with higher technology manufacture (e.g. autoclave moulding of unidirectional glass fibre), the aerospace industry.



Composites have an advantage over other materials because they can be molded into complex shapes at relatively low cost. This gives designers the freedom to create any shape or configuration. Boats are a good example of the success of composites.

Design flexibility

Composites products provide long-term resistance to severe chemical and temperature environments. Composites are the material of choice for outdoor exposure, chemical handling applications, and severe environment service.

Corrosion Resistance



One reason the composites industry has been successful is because of the low relative investment in setting-up a composites manufacturing facility. This has resulted in many creative and innovative companies in the field.

Low Relative Investment

Composite products and structures have an exceedingly long life span. Coupled with low maintenance requirements, the longevity of composites is a benefit in critical applications. In a half-century of composites development, well-designed composite structures have yet to wear out.

Durability

In 1947 the U.S. Coast Guard built a series of forty-foot patrol boats, using polyester resin and glass fiber. These boats were used until the early 1970s when they were taken out of service because the design was outdated. Extensive testing was done on the laminates after decommissioning, and it was found that only 2-3% of the original strength was lost after twenty-five years of hard service.


Disadvantages of Composites

The experience and intuition gained over the years about the behavior of metallic materials does not apply to composite materials.

properties in composites vary from point to point in the material. Most engineering structural materials are homogeneous.

Composites are heterogeneous

Composites are highly anisotropic

The strength in composites vary as the direction along which we measure changes (most engineering structural materials are isotropic). As a result, all other properties such as, stiffness, thermal expansion, thermal and electrical conductivity and creep resistance are also anisotropic. The relationship between stress and strain (force and deformation) is much more complicated than in isotropic materials.


Disadvantages of Composites

Composites materials are difficult to inspect with conventional ultrasonic, eddy current and visual NDI methods such as radiography.

American Airlines Flight 587, broke apart over New York on Nov. 12, 2001 (265 people died). Airbus A300’s 27-foot-high tail fin tore off. Much of the tail fin, including the so-called tongues that fit in grooves on the fuselage and connect the tail to the jet, were made of a graphite composite. The plane crashed because of damage at the base of the tail that had gone undetected despite routine nondestructive testing and visual inspections.


Disadvantages of CompositesIn November 1999, America’s Cup boat “Young America” broke in two due to debonding face/core in the sandwich structure.