A composite material (also called a composition material or shortened to composite, which is the common name) is a material which is produced from two or more constituent materials SeminarKHP-6sem.ppt

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Composite Materials and Mechanics
K. H. Prakash
VI
th
Sem,M.Tech. (P.D.M)
Reg No –5VW02MDZ09
Department of PG Studies, VTU, Belgaum
Regional Centre : BMSCE, Bangalore

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Composite Materials
Preliminaries
•Definitions
•Properties to be improved
•Classification of composites
•Mechanical behavior of a lamina

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COMPOSITE MATERIALS
•Definition : Two or more materials combined
on a macroscopic scale to form a useful third
material
• Properties to be Improved :
Strength, stiffness, weight, fatigue life, wear
resistance, thermal insulation, thermal
conductivity, corrosion resistance, acoustical
insulation, etc.

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CLASSIFICATION OF
COMPOSITE MATERIALS
•Fibrous composites : Fibers in a matrix
•Particulate composites : Particles in a
matrix
•Combinations of above : Reinforced fiber-
reinforced composite
•Laminated composites : Layers of various
materials (nano-composites)

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CLASSIFICATION OF
COMPOSITE MATERIALS

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LAMINATED FIBER-REINFORCED
COMPOSITE MATERIALS
•Lamina : Basic building block; flat or
curved arrangement of unidirectional or
woven fibers in a matrix
•Fiber : Load-carrying agent
•Matrix : Supports and protects fibers, and
transfers load between broken fibers

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ADVANTAGES OF COMPOSITES
•New and simpler fabrication techniques
unique to composites enable: reduced
machining, reduced material waste, fewer
parts, and reduced assembly time.
•Lower cost of fabrication more than offsets
higher cost of raw material

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ADVANTAGES OF COMPOSITES
(continued)
•Cost in weight-sensitive : Better
applications; easier fabrication; going down
with higher production (usage) and new
technology
•Time : Shorter fabrication time; faster
cooling; coefficient of expansion of tool
matches part

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COMMERCIAL APPLICATIONS
•Sporting Goods
• Tennis Rackets • Golf Clubs
• Skis • Bikes
• Transportation
• CARS • SPACE VEHICLES (Parts Of)
• TRUCKS• SHIPS (Parts Of)
• Railroad Cars
• Machinery
• LOW INERTIA PARTS, E. G., Loom Shuttle
• Energy Generation Or Storage Devices
• Windmills • Flywheels

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PROBLEM AREAS IN COMPOSITES
•Characterization of material properties :
static, dynamic, fatigue, fracture,
temperature, moisture, electrical, etc.
•Analyses : Directional nature of response;
different load-response coupling (shear-
extension, bend-twist, bending-extension);
many layers versus one

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PROBLEM AREAS IN COMPOSITES
( continued )
•Bonded and bolted joints
•Holes in laminates
•Fracture mechanics
•Optimization
•Interlaminar stresses
•Nonlinear material behavior
•Inspection techniques

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Composites Thinking
Always expect surprises relative to often
inapplicable Intuition based on behavior of
(isotropic) metals

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Mechanics of Composite Materials
•Characterization of a Lamina
•Laminate Theories -
•An Overview
•Classical Laminate Plate Theory
•Firs-Order Laminate Plate Theory

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CHARACTERIZATION OF A LAMINA

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ANALYSIS OF COMPOSITES
STRUCTURES
•Directional nature of response
•Different load-response coupling (shear-
extension, bend-twist, bending-extension)
•Many layers versus one

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ELEMENTS OF ANALYSIS
•Determine Pertinent Structural Response
Parameters:
•Deflections
•Buckling loads
•Vibration frequencies
•Stresses
Full-field stresses
Stresses around cutouts
Stresses around defects

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FAILURE ANALYSIS
Are the structural response parameters
within design bounds ?
•Deflections too high?
•Buckling loads too close?
•Vibration frequencies near resonance?
•Stresses too high? Less than strength?
•Joints (can loads be transmitted?)

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Mechanical of Isotropic and
Orthotropic Materials

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Contracted Notation for Stresses and Strains

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Strain-Stress Relations

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Plane-Stress State

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Plane-Stress Constitutive Equations

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Strain-Stress Relations in Reference
Coordinates

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REFERENCES
•Mechanics of Composite Materials , 2
nd
Ed., R. M.
Jones, Taylor & Francis, PA, 1999 (basic
introduction to the anisotropic elasticity and
composite materials)
•Mechanics of Laminated Composite Plates and
Shells , J. N. Reddy, CRC Press, 2004
(introduction to the theory and analysis -
analytical as well as FEM -of laminated
composite plates and shells)