v SANDWICH
STRUCTURE PROCESSING:
Definition:
Panels
composed of a light weight core material like honey comb, foamed plastic etc.
to which relatively thin, dense, high strength faces or skins are adhered to
produce material with lower and lower density and higher and higher stiffness.
Honey
comb:
Manufactured
product consisting of sheet metal or a resin impregnated sheet material (paper,
fibrous glass etc.) which has been formed into hexagonal shaped cells.
v FOAM RESERVOIR
MOULDING (FRM) or ELASTIC RESERVOIR MOULDING (ERM):
Process:
a.
It
is a method of preparing a sandwich structure.
b.
An
open cell urethane foam is impregnated with a controlled amount of epoxy or
other structural resins.
c.
Dry
glass fabric or mat facing sheets are placed on either side of the foam and the
assembly is placed in a mould.
d.
As
the mould closes the dry glass is pressed by the foam against the mould surface
and the air from the foam is escaped through the dry glass.
e.
When
the mould is closed, the resin escapes from the foam and saturates the facing
sheets.
f.
After
curing, the laminate with considerably low density (than FRP) results.
g.
Advantages:
The physical properties are superior to SMC parts and lower pressures than SMC
parts is used.
h.
Capital
investment for large presses is less, hence saving is considerable.
i.
Process
cannot be used for parts with sharp curves, ribs or bosses.
j.
Fabrication
of automobile body parts is made by FRM
Sandwich
structures are also made by using an integrally woven 3-dimensional structure,
with the facing attached to the core during the weaving operation.
Additional compression and
bending strength can be obtained by placing foam or PP inserts between the
webs. The woven structure can ne impregnated before or after the inserts are in
place. However, curing is done after the inserts are placed. The foam inserts
are usually not removed to get additional strength while PP inserts are removed
to minimize the weight with the hollow core.
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