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Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP or ETFE) Surface Breather Nylon Vacuum Bag 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. Breathe Volatiles Out??? Vent Air In?
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Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP.

Dec 16, 2015

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Bradyn Whitfill
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Page 1: Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP.

Vacuum/VentLine

TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS

Edge Sealant(Tacky Tape)

EdgeBreather Part Layup

Mold

Parting Film(FEP or ETFE)

SurfaceBreather

NylonVacuumBag

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.

BreatheVolatilesOut???

VentAirIn?

Page 2: Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP.

Conventional Composites Fabrication - 1965 - 1998Traditional Layup and Vacuum Bag - Every Part In Every Airplane

Edge Sealant (Disposable)

Thermocouples (Two per part, disposable)

Grit Strips for Ply Tiedowns

Edge Breather/ Bleeder (Disposable)

Excess Graphite On EVERY part to Prevent Core Movement (Multiple Ply Staggers)

Hand-Installed Vacuum Probes

FEP Parting Film (Disposable)

Surface Breather (Disposable)

Nylon Vacuum Bag (Disposable)

All Steps Shown Must Be Re-Done for Every Part

Page 3: Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP.

Vacuum/VentLine

STANDARD SILICONE RUBBER VACUUM BAG WITH EDGE AND SURFACE BREATHERS(Replace Nylon Bag and Edge Sealant With Reusable

Silicone Rubber Diaphragm and Integral Seal)

RubberEdge Seal

EdgeBreather Part Layup

Mold

Parting Film(FEP or ETFE)

SurfaceBreather

ReusableSiliconeRubberVacuum Bag

This concept used for years – the question is WHY does it work? Same breather path concept as Nylon bag with breathers, or something else?

BreatheVolatilesOut???

Vent Air In?

BagFrame

Page 4: Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP.

SameBag

Close-Up of Sealand Gas Springs

EXAMPLE SYSTEMS OF SILICONEVAC BAGS REQUIRING BREATHERS

Page 5: Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP.

Vacuum/VentLine

SILICONE PRESSURE PAD/NYLON BAG(FIRST PROOF OF NO-BREATHER VACUUM BAGGING CONCEPT)

Edge Sealant(Tacky Tape)

EdgeBreatherEliminated

Part LayupMold

Parting Film(FEP or ETFE)

SiliconeRubberPressure Pad(Surface BreatherEliminated)

NylonVacuumBag

Silicone Rubber Pressure Pad Substituted for Breather Material.

Parts Came Out Looking Beautiful. No Breathers Used. Why Does It Work?

BreatheVolatilesOut???

VentAirIn?

1

2 ProbePad

Page 6: Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP.

Vacuum/VentLine

STANDARD SILICONE RUBBER DIAPHRAGM, NO BREATHERS(Does Not Produce Good Parts – WHY?????????)

RubberEdge Seal

Part LayupMold

Parting Film(FEP or ETFE)

ReusableSiliconeRubberVacuum Bag

BagFrame

Now We Switched to Standard Silicone Rubber Vacuum Bag

Over FEP – No BreatherPart Showed Horrible Porosity

ProbePad

Page 7: Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP.

Vacuum/VentLine

STANDARD SILICONE RUBBER DIAPHRAGM, NO BREATHERS(Does Not Produce Good Parts Without Nitrogen Barrier Layer)

RubberEdge Seal

Part LayupMold

Parting Film(FEP or ETFE)

ReusableSiliconeRubberVacuum Bag

BagFrame

Why A Standard Silicone Rubber Vacuum Bag Over FEP Does Not

Work:Autoclave Nitrogen Permeates

Through Silicone, Through FEP, And Into Part, Causing Porosity

AUTOCLAVEATMOSPHERE

(Nitrogen, 350F, 45 Psi)

Page 8: Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP.

Vacuum/VentLine

SILICONE PRESSURE PAD/NYLON BAG(Same as Slide 3, Works Due to Nitrogen Barrier Effect of Nylon Vac Bag)

Edge Sealant(Tacky Tape)

EdgeBreatherEliminated

Part LayupMold

Parting Film(FEP or ETFE)

SiliconeRubberPressure Pad(No Surface Breather)

NylonVacuumBag

Nylon bag acts as gas barrier layer. Pressure pad provides superior

bagside surface. No edge or surface breathers required.

1

2 ProbePad

AUTOCLAVEATMOSPHERE

Page 9: Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP.

Vacuum/VentLine

SILICONE/VITON DIAPHRAGM, NO BREATHERS(No Breathers – Viton Layer is a BarrierWithin a Reusable Vacuum Bag System)

RubberEdge Seal

Part LayupMold

Parting Film(FEP or ETFE)

Silicone/Viton Vacuum Bag(Black Outer Layer Is Viton)

BagFrame

Viton Layer Outside Silicone Diaphragm Acts As A Barrier, Preventing Autoclave Nitrogen

From Reaching Part and Causing Porosity

AUTOCLAVEATMOSPHERE

Page 10: Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP.

ASTM D1434 NITROGEN GAS PERMEABILITY(cc/m2/24hr @ 1 atm)

Material 73F 125F

.004" Nylon Bagging Film 1 18

.002" Nylon Bagging Film <5 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

Page 11: Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP.

8-256, 8-256, 8-168, 8-168,No Edge w/ Edge No Edge w/ EdgeBleed 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

Percent 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

“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:

Page 12: Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP.

"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.

"SNAPPY CAUL PAD" – Silicone/Nylon Breatherless Vacuum Bag

• 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

FIRST PRODUCTION APPLICATION

Page 13: Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP.

Lay-UpMandrel

Lay-UpMandrel

Lay-UpMandrel

Lay-UpMandrel

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

VacuumProbesNot Shown

Page 14: Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP.

Silicone/Viton - Optimum Material, Labor Reduction

FromThis

ToThis

Std Bag – FEP, Edge Brthr, Surf Brthr, Nylon Bag,(all throwaway), install vac probes by hand

Viton Bag – Apply FEP, then simply close bag

Why It Works – Viton layer on backside of siliconeProduction Model in St. Louis on F-18 Panel

1 2

34

Page 15: Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP.

SUMMARY OF ACCOMPLISHMENTS – CHANGES TO BAC 5317Applicable 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

Page 16: Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP.

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)

• "Ultimate answer is an impermeable release film - then we could convertstandard silicone vac bags to breatherless bags (no Viton layer required)(So far impermeable release films have not been found)

Vacuum/VentLine

The Ultimate Answer:An impermeable release filmthat could be simply placed underexisting silicone rubber diaphragms,eliminating need for breathers

Impermeable release film acts asnitrogen barrier (same effect as Viton)