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the part a sandwiched laminate was developed. A light
weight core material is sandwiched between two thin layers
of a flat laminate. The core may be foam or a honeycomb
shaped material. Common honeycomb materials
are aluminum foil, and a paper-like organic material called
Nomex®. Sandwiched panels are easy to recognize because
of the core. Flight control panels and various other
panels are common applications for the sandwiched
panel. Nose radomes have also been made using core
material. (Photos 13 thru 15)
(c) FILAMENT WOUND LAMINATE. Cylindrical,
round or shell shaped parts are made by winding resinwet
fiber from a roving of fiber over a mandrel to get the
desired shape. Each pass is called a layer. The process
has the flexibility to tightly wind the fibers in various patterns.
Different winding patterns have different strengths.
The more tightly wound, the greater the strength the part
will have. Storage tanks, tubes, gas cylinders (liquid oxygen
bottles, LOX), rocket motors and nose radomes are
filament wound.
Filament wound parts are easy to recognize because of
the winding pattern. It may still be in one piece after the
damage has occurred. Under severe impact damage the
winding pattern will unravel and the layers will begin to
separate. Complex winding patterns will reduce the release
of fibers. (Photo 16)
(d) HYBRID LAMINATES. It was most common to build
aircraft components from unidirectional tape with a surface
layer of woven fabric. Advanced materials and
manufacturing techniques now include hybrid composite
systems (stacking with varying types of material) with
complex shapes. The design may include a metal-coated
TO 00-105E-9
fiber, the resin may contain metal particulate or a metal
mesh layer may be incorporated between the layers to
protect against lightening strikes. New aircraft and redesigns
for existing aircraft are being manufactured using
advanced applications. Except to see more composites
at the mishap site because of this.(Photo 17)
(5) FIBER - RESIN DETAILS. The strength of the composite
system is in the fiber direction. The amount depends
on the number of very small diameter size fibers
(micron range) within the tape. Prepreg material contains
thousands of long continuous length fibers. Laminate
thickness can vary. The number of prepreg layers
can range from less than 10 to more than 50. A quarter
inch thick, four-inch square composite made from a fourinch
tape prepreg1 could have over 4 million fibers.
Prepreg tapes are manufactured with a very specific
amount of fiber to resin weight. The system will contain
more fiber weight than resin weight. A typical weight ratio
is 65% fiber to 35% resin. For example, the F-16C/D
contains approximately 200lbs of composite. If the composites
were made from just prepreg tape, 130lb of the
composite would be fiber weight.
(6) SUMMARY. A composite is a system of materials
– fibers and a polymeric resin or plastic. Without the
interaction of each material within the system, the system
would not be able to perform.
a Psuedo-homogenous solid. The solid laminate
looks like a homogenous solid in the cured state.
b One way of building a composite is to stack multiple
layers of material.
c Ready-to-build materials are unidirectional, woven
fabric, and roving “prepreg” and metallic or organic paper-
like core material.
d Each tape layer has thousands of long continuous
length fibers and the finished part contains millions of
individual fibers.
e The system is made with a specific amount of fiber
to resin weight.
f Various types of parts can be made from layering of
materials: solid laminate, sandwich laminate filament
wound laminate or the hybrid laminate.
g Re-designs may have used composite materials.
Except to see more composites parts at a mishap site
than what may be found in the documentation.
h Terms used to describe the material at various stages
of manufacturing or repair.
o prepreg tape
o layers or plies
o stack
o filament wound
o solid laminate
o sandwich laminate
o hybrid laminate
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b. MISHAP- COMPOSITE DAMAGE. An undamaged
composite looks and behaves like a homogenous solid.
It is almost impossible to determine if the material is a
composite under the coatings unless the design includes
a textured surface layer like a woven fabric. When the
composite is damaged it becomes obvious it is a “SYSTEM”
1 of materials. When damaged, the materials within
the system begin to separate.
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