Vacuum/

1
TRADITIONAL NYLON VACUUM BAG WITH EDGE AND
SURFACE BREATHERS
This concept, the prevailing vacuum bag process
since the 1950's, is based on the incorrect
theory that porosity will occur unless a breather
path is present to vent air in and breathe
volatiles out.
Nylon Vacuum Bag
Surface Breather
Vacuum/ Vent Line
Parting Film (FEP or ETFE)
Breathe Volatiles Out???
Vent Air In?
Edge Breather
Layup Mold
Part
Edge Sealant (Tacky Tape)
2
Conventional Composites Fabrication - 1965 - 1998
Traditional Layup and Vacuum Bag - Every Part In
Every Airplane
All Steps Shown Must Be Re-Done for Every Part
Hand-Installed Vacuum Probes
Nylon Vacuum Bag (Disposable)
Edge Breather/ Bleeder (Disposable)
Surface Breather (Disposable)
Excess Graphite On EVERY part to Prevent Core
Movement (Multiple Ply Staggers)
FEP Parting Film (Disposable)
Grit Strips for Ply Tiedowns
Edge Sealant (Disposable)
Thermocouples (Two per part, disposable)
3
STANDARD SILICONE RUBBER VACUUM BAG WITH EDGE
AND SURFACE BREATHERS (Replace Nylon Bag and Edge
Sealant With Reusable Silicone Rubber Diaphragm
and Integral Seal)
This concept used for years the question is WHY
does it work? Same breather path concept as
Nylon bag with breathers, or something else?
Reusable Silicone Rubber Vacuum Bag
Bag Frame
Vacuum/ Vent Line
Surface Breather
Parting Film (FEP or ETFE)
Breathe Volatiles Out???
Vent Air In?
Edge Breather
Rubber Edge Seal
Layup Mold
Part
4
Same Bag
EXAMPLE SYSTEMS OF SILICONE VAC BAGS REQUIRING
BREATHERS
Close-Up of Seal and Gas Springs
5
Silicone Rubber Pressure Pad Substituted for
Breather Material. Parts Came Out Looking
Beautiful. No Breathers Used. Why Does It Work?
SILICONE PRESSURE PAD/NYLON BAG (FIRST PROOF OF
NO-BREATHER VACUUM BAGGING CONCEPT)
1
Silicone Rubber Pressure Pad (Surface
Breather Eliminated)
Nylon Vacuum Bag
Vacuum/ Vent Line
Parting Film (FEP or ETFE)
Breathe Volatiles Out???
Vent Air In?
2
Edge Breather Eliminated
Probe Pad
Layup Mold
Part
Edge Sealant (Tacky Tape)
6
STANDARD SILICONE RUBBER DIAPHRAGM, NO
BREATHERS (Does Not Produce Good Parts
WHY?????????)
Now We Switched to Standard Silicone Rubber
Vacuum Bag Over FEP No Breather Part Showed
Horrible Porosity
Reusable Silicone Rubber Vacuum Bag
Bag Frame
Vacuum/ Vent Line
Parting Film (FEP or ETFE)
Probe Pad
Rubber Edge Seal
Part
Layup Mold
7
STANDARD SILICONE RUBBER DIAPHRAGM, NO
BREATHERS (Does Not Produce Good Parts Without
Nitrogen Barrier Layer)
Why A Standard Silicone Rubber Vacuum Bag Over
FEP Does Not Work Autoclave Nitrogen Permeates
Through Silicone, Through FEP, And Into Part,
Causing Porosity
Reusable Silicone Rubber Vacuum Bag
AUTOCLAVE ATMOSPHERE (Nitrogen, 350F, 45 Psi)
Bag Frame
Vacuum/ Vent Line
Parting Film (FEP or ETFE)
Rubber Edge Seal
Part
Layup Mold
8
SILICONE PRESSURE PAD/NYLON BAG (Same as Slide 3,
Works Due to Nitrogen Barrier Effect of Nylon
Vac Bag)
Nylon bag acts as gas barrier layer. Pressure
pad provides superior bagside surface. No edge
or surface breathers required.
AUTOCLAVE ATMOSPHERE
1
Silicone Rubber Pressure Pad (No Surface Breather)
Nylon Vacuum Bag
Vacuum/ Vent Line
Parting Film (FEP or ETFE)
2
Edge Breather Eliminated
Probe Pad
Layup Mold
Part
Edge Sealant (Tacky Tape)
9
SILICONE/VITON DIAPHRAGM, NO BREATHERS (No
Breathers Viton Layer is a Barrier Within a
Reusable Vacuum Bag System)
Viton Layer Outside Silicone Diaphragm Acts As A
Barrier, Preventing Autoclave Nitrogen From
Reaching Part and Causing Porosity
Silicone/Viton Vacuum Bag (Black Outer Layer Is
Viton)
AUTOCLAVE ATMOSPHERE
Bag Frame
Vacuum/ Vent Line
Parting Film (FEP or ETFE)
Rubber Edge Seal
Part
Layup Mold
10
ASTM D1434 NITROGEN GAS PERMEABILITY (cc/m2/24hr
_at_ 1 atm)
Material 73F 125F .004" Nylon Bagging
Film 1 18 .002" Nylon Bagging Film lt5 16-40 .001
" White Tedlar 10 66 .001" FEP Release
Film 1900 10200 .085" Silicone
Rubber 8100 12000 .036" Silicone
Rubber 14400 21200 .030" Viton
Fluoroelastomer 15 151
11
Apples vs. Apples Volatile Escape Evaluation
in BAC 5317 Cure
Macro Volatiles Test With Large (12" x 12")
Laminates Fabricated 15-ply 8-168 and 11-ply
8-256 laminates, with and without edge breather,
otherwise standard BAC 5317 vacuum bag using
nylon bagging film. Weighed prepreg (and edge
bleeder) before and after cure
8-256, 8-256, 8-168, 8-168, No Edge w/ Edge No
Edge w/ Edge Bleed Bleed Bleed Bleed Weight
Before Cure, Grams 335.1 371.0 470.2 502.7 Weight
After Cure, Grams 334.8 370.9 469.2 503.0 Perc
ent Weight Loss 0.09 0.03 0.21 -0.06
Traces of excess resin remained on toolside FEP
after debagging when no edge bleed used,
indicating that no mass was actually
lost. CONCLUSION Volatiles Remain In Part,
Edge Bleeders Do Not Remove Them
12
FIRST PRODUCTION APPLICATION
"SNAPPY CAUL PAD" Silicone/Nylon Breatherless
Vacuum Bag
"Snappy Caul Pad" Concept no surface
breather Add only nylon bag over the silicone
pressure pad shown. Integral port-to-port
breather path not shown.
In production on Frederickson 777 rib panels
Successfully demonstrations on Tulsa 777 floor
panels (above) Being demonstrated for 7E7 floor
panels Applicable to most C-Channel shaped
parts
13
Vacuum Probes Not Shown
APPLICATION OF VACUUM WITH A SNAPPY CAUL PAD As
laid up, prior to applying vacuum FEP,
Pressure Pad, Nylon bag, No Surf Breather Note
silicone pressure pad (orange) "tented" over
part Nylon bag laid loosely over caul (wrinkles
OK) 15-30 minutes labor savings over
hand-cut breather
Vacuum applied, bag starts to draw down
Bag pulls tight on caul pad, producing tension
to pull prepreg radius down tightly
Bag has pulled down tightly, ready for cure
Faster to apply Better radius quality Better
bagside surface finish
14
Silicone/Viton - Optimum Material, Labor
Reduction
1
2
From This
To This
Std Bag FEP, Edge Brthr, Surf Brthr, Nylon
Bag, (all throwaway), install vac probes by hand
Viton Bag Apply FEP, then simply close bag
3
4
Why It Works Viton layer on backside of silicone
Production Model in St. Louis on F-18 Panel
15
SUMMARY OF ACCOMPLISHMENTS CHANGES TO BAC
5317 Applicable to All Global Processors
1) Edge breather/bleeders optional, need not be
used they play no role in part cure,
quality 2) Back pressure under vacuum bag
during cure no longer requires a rejection
tag 3) Surface breathers optional in
Silicone/Nylon or Silicone/Viton vac bag
configurations (Production usage in Winnipeg,
Frederickson, Tulsa, and St. Louis) 4) ETFE
parting film qualified and accepted 15-25
savings over FEP "Fluoro-Lease" parting film
qualified 2003 handling of FEP at price of
ETFE 5) Polyester and Nylon Breathers made
open source lower weights, new suppliers
16
Remaining Work I Would Like To Do
Develop capability to apply formed Viton layer
(currently flat piece is cocured with silicone
diaphragm) Resolve issue of apparent leak
check with breatherless vacuum bags (Issue is
lack of volume under bag, is resolvable) "Ultim
ate answer is an impermeable release film - then
we could convert standard silicone vac bags to
breatherless bags (no Viton layer required) (So
far impermeable release films have not been found)
Impermeable release film acts as nitrogen barrier
(same effect as Viton)
The Ultimate Answer An impermeable release
film that could be simply placed under existing
silicone rubber diaphragms, eliminating need for
breathers
Vacuum/ Vent Line