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Composite Defined
- The term composite is used to
described two or more materials that
are combined to form a structurethat is much stronger than the
individual components.
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Combination of Composite
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Composite Materials
Matrix
Core Materials
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Advantages of Composite
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* High strength to weight ratio
* Strong as a metal part
* Reduced drag* Number of parts and fasteners may bereduced
* Composites dont corrode like metal does.
* Reduced wear
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Uses of Composites
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* Helicopters
* Military Aircraft
* Commercial Aircraft
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Kinds of Reinforcing Fibers
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1. Fiber Glass (Glass cloth)
2. Aramid
3. Carbon / Graphite4. Boron
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- is made from small strands ofmulti silicon glass that are span
together and woven into cloth.
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Fiber Glass (Glass cloth)
- widespread availability and itslow cost make fiber glass one of the
most popular re-enforcing fibers.
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- also known as Electric Glass for its high
electrical resistance.- it is a borosilicate glass commonly used for
re-enforcement because of its low cost andgood strength characteristics.
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a. E - Glass
b. S - Glass- it is a magnesia alumina silicate glass that
is up to 40 percent stronger that E-Glass and Retain
its strength characteristics at higher temperature.- S Glass is used were a very high tensile
strength fiber glass is needed.
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c. C- Glass
- is used in materials that
require chemical resistance.
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- is usually characterized by its yellowcolor, light weight tensile strength and
remarkable flexibility.
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Aramid / Kevlar
- Bullet proof according to the
grade.
Example:Kevlar 129 is bullet proof material
Kevlar 29 is used for boats.
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- is a very strong, stiff re-enforcement.
- this black is very strong, stiff andused for its rigid strengthcharacteristics.
- electrically conductive.
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Carbon / Graphite
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- is made by depositing the element
boron into a thin filament of
tungsten.- has excellent compressive strength
and stiffness and is extremely hard.
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Boron
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- are used when a high temperature
application is needed.
- retains a temperature of 2, 200F.
Examples:
Ceramic is used for the tile of the space
shuttle.
- dissipates the heat quickly.
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Ceramic
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- the selective placement of fibers needed to
obtain the greatest amount of strength in various
application.
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Fiber Science
Victors of fiber placement
1. 0 plies (to react the axial loads) warp
2. 45 plies (react to shear victors) bias3. 90 plies (to react to side loads) wft
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1. Resin
2. Catalyst / Hardener
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MatrixMaterials
Two (2) types of Plastic Risens
1. Thermoplastics use heat to form the past intothe desired shape.
Example: Aircraft Windshield
2. Thermo set resins use heat to force and setthe shape of the part permanently
Example: Structural airframe application
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- are type of thermo setting plastic resin well
known for their outstanding adhesion, strength
and their resistance to moisture and chemicals.
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Epoxy Resin System
- most common matrix system used in composite
fabrication and repair, because:
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1. Extremely flexible in terms of their
applications.2. Exhibits good adhesive characteristics
when used with a broad range of cloth
re-enforcing materials, fillers andsubstrates.
3. After being cared, epoxy resins are
resistance to deterioration by water,acids, bases many chemicals solvents and
Vice Versa.6/20/2012 16
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4. Epoxy resins are easily cased at room
temperature or at slightly elevatedtemperatures and they do not require
exotic equipment to process.
5. Epoxy resins are very dimensionallystable they shrink very little during the
curing process and very acceptable for
use of structural parts, mold fabricationmaterial, or tooling fabrication material.
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6. The resins exhibit the strategist
adhesive characteristics of any known
polymeric material.
7. Superior strength long shelf if more
economical for fabrication and repair.
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- when working with resins and catalyst or caring
agents, always follow the procedures specified in
the structural repair manual.- if the resin system requires refrigerated storage
allow each part to warm up to room
temperature before weighing and mixing.
- mix resins in proper ratios.
- mix resins for the proper amount of time
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Working with resin and Catalyst
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- do not mixed large amounts together.
- all resins care by chemical reaction, but some
generate their own heat, thus accelerating the
curing.
- be sure to know the resins pot life beforestarting .
- spread the matrix all over the lay-up in proper
amount to avoid resin rich on resin lean.
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- are thixotropic agent are materials
that are added to resins to control
viscosity and weight, to increaseprofile and strength and to make the
applications of the resin easier.
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Fillers
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1. Micro Balloons are small
spheres of plastic or glasses.
2. Chopped fibers or flox type of
fiber cut into a desired length.
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Types of Fillers
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- are fabrics that have the resin system
already impregnated into the fabric.
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Pre-impregnated Materials
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1. The pre-preg contains the proper
amount of matrix.
2. The re-enforcing fibers are completelyencapsulated with the matrix.
3. Pre-preg fabric eliminates the use to manually
weigh and mix components.4. Pre-preg materials produce a stronger
component or repair.
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Advantages of the Pre-Pregs
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1. Many pre-pregs must be stored in a freezer.2. Many companies do not want to sell small
quantities of a specific weave and resin system,
so a full roll must be purchased.
3. Pre-pregs material is much more expensive
than raw fabric that can be impregnated with the
resin system.
4. Composite components and materials have not
yet been standardized.
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Disadvantages of the Pre-Pregs
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- it is the central member of anassembly.
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Core Materials
Types of Core Materials
- Honeycomb
- Foams
- Balsa wood
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Why use core material?
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Why use core material?
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- this must be applied to the surface
during the curing operation until the
component is fully cured. The
purpose of applying mechanical
pressures is to:
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Applying Pressures
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1. Remove excess resin from the
components ensuring the proper ration of
resin to fiber re-enforcement.
2. Remove air trapped between layers.
3. Maintain the contour of the repairrelative to the original part.
4. Hold the repair securely, preventing any
shifting of the patches during the curingprocess.
5. Compact the fiber layers together.
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a. Shot bags
b. Clecos
c. Spring Clamps
d. Vacuum Bagging
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Methods of Applying Pressures
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- this must be applied to the surface
during the curing operation until the
component is fully cured.
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Shot Bags
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- used in conjunction with pre-shaped
cauls plates to apply pressure to the
repair.
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Clecos
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- allow the pressure to continue even
after the res in flow.
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Spring Clamps
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- the most effective method of
applying pressure to a repair and is
recommended for the use whenever
possible.
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Vacuum Bagging
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- once the repair is made and the
patches in place, the area is covered
with a parting film or a parting fabric(Peel Ply)
- a bleeder material is an absorbent
material that is either placed around
the edges.
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Vacuum Bagging Process
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- a breather material is placed on
one side of the repair to allow air toflow through it and up through the
vacuum valve.
- the two vacuum valve is placed on
top of the breather material to
remove the air from inside thevacuum bag.
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- a sealant type is attached around
the edges of the repair.
- vacuum bagging film is laid out therepair area and the edge are worked
out into the sealant tape to producea airtight seal.
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- the bagging film should be slightly
pressed into the tape until it forms
an airtight seal that covers the part.
- a slit is cut into the bagging film
over the vacuum base, then thevacuum valve is inserted into the
base and sealed airtight.
- the vacuum source is connected to
the vacuum hose and turned on.
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- it is done to make sure the bag is
sealed properly.
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Vacuum Leak Check
Vacuum bagging Films
- are used to cover the components
an seal out air.
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- are used to maintain a positive seal
between the surface of the original
part and the bagging films.
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Sealant Tape
Peel Ply- a nylon or polyester release fabric may
be used next to the wet resin during
operation to transfer excess resin to the
bleeder material without sticking to the
part.
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- are cotton like absorbent materialused to soak up excess resins.
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Bleeders
Breathers
- are cottony materials that allow air to
flow through a valve or over the surface ofthe part throughout the vacuum bagged
area.
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a. Room temperature curingb. heat curing
c. Step curing
d. ramp and Soak curinge. Hear blanket
f. heat guns
g. Heat lamps
h. Oven Curing
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Methods of Curing
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- some repairs may be cured at room
temperature from 65 - 80 F over a
time span of 8-24 hours, depending
on the type of resin system used.
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Room Temperature Curing
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- the most widely accepted method
of curing structural composites,
employs resins that cure only at
higher temperature.
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Heat Curing
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- is used with a manually operated
controller and requires the
technician to make the adjustments
manually at specific time intervals.
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Step Curing
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- a programmable controller
produces a more sophisticated and
accurate curing than the step curing
process.
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Ramp and Soak Curing
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- are probably the most widely
accepted form of applying heat to a
composite component for the work.
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Heat Blankets
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- have been used to cure composite
parts for many years
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Heat Lamps
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Classification of damage:*Cosmetic Defects a defects on the
outer surface that does not involve
damage to the structural reinforcingfibers.
* Impact damage occurs when aforeign objects strikes the part.
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Assessment and Repair
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*Delamination is the separation of
fabric layers of materials in a
laminate
*Cracks occur in advanced
composite structures just as inmetallic ones.
* Hole damage occur from impact,over-torquing fasteners, or a result
of fasteners pull-through.6/20/2012 53
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1. Visual Inspection - used to detectscracks surface irregularities and
surface detects such as delamination
and blistering.2. Coin tap test one of the most
important tools used to detectinternal flaws or delamination.
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Inspection methodology
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Algie composite airframe
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Lancair ES composite parts
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Velocity composite parts
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