COMPOSITE MATERIALS
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What are composite materials? Two or more materials bound together
Example from civil engineering: Concrete reinforced with steel bars
Reinforced concrete wall
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COMPOSITE MATERIALS
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Fiber reinforced composite materials
Reinforcement: Main load carrying member
Binding material:transfers load to fibers, keeps the fiber together
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FIBER MATERIALS
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• A Fiber (reinforcement) may be defined as an elongated stringy man-made material.
• A polymer (matrix) is a large molecule consisting of repeating units connected by
covalent chemical bonds.
• Once the polymer is combined with the fibers, the polymerization process must take
place in order to obtain a solid structural composite material.
• Another critical issue is the fiber-matrix bonding. When the composite material is
loaded, both fibers and matrix must be strongly bonded so that they work as a solid
rigid.
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FABRIC ARCHITECTURES
Woven
Unidirectional
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COMPOSITE LAMINATES
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SANDWICH CONSTRUCTION
When loads are applied to any beam, such as wing spar most stress occurs at the
outer surfaces.
• Therefore, SANDWICH structure is commonly used in composite construction
to increase the thickness without significant weight penalty
Core material:
Honeycomb
Balsa wood
Foam etc.
Valid for honeycomb cores
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Typical SANDWICH structure
Bonding material between layers:
Epoxy resin
Core material:
Honeycomb, wood, foam etc.
Upper and lower layers:
Composite material composed of suitable fiber + matrix combination
Typical fiber materials:
E-Glass: Standard fiber glass; workhorse of composites, moderate strength, good
bonding with epoxy, cheap
Kevlar: Organic fibers, high impact resistance, high strength, difficult to work, poor
bonding with epoxy, moderate prize
Carbon: 93-95% carbon content, very high strength and fatigue resistance, excellent
bonding with epoxy, expensive
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Typical resin(matrix) materials:
Epoxy: Excellent adhesion to fibers, highest strength, low shrinkage, will bond to
dissimilar or already cured materials
Vinly ester: Moderate strength, more resistant to degradation from water/moisture
Polyester: Low strength , fast curing times, exhibit shrinkage, low weathering resistance,
cheapest (non adequate for advanced composites: poor adhesion to carbon and Kevlar)
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COMPOSITE MANUFACTURING
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COMPOSITE MANUFACTURING
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COMPOSITE MANUFACTURING
INFUSION
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COMPOSITE MANUFACTURING
INFUSION APPLICATIONS
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COMPOSITE MANUFACTURING
VACUUM BAGGING
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COMPOSITE MANUFACTURING
VACUUM BAGGING
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COMPOSITE MANUFACTURING
VACUUM BAGGING
•Release agent: facilitates the extraction of the part.
•Peel ply: leaves the part surface apt to be bonded or painted.
•Prepreg.
•Release film: prevents the resin to reach the bleeder fabric but not the volatiles.
•Bleeder fabric: takes out the excess of resin in order to get the desired fiber fraction.
•Breather fabric:
makes the
vacuum uniform
along the part.
•Vacuum
bag/seal: seals the
cavity to be
vacuumed.
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