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Vacuum/ Vent Line

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.

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Vacuum/ Vent Line

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  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 incorrecttheory 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 Surface Breather Vacuum/ Vent Line 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. Nylon bag acts as gas barrier layer. Pressure pad provides superior bagside surface. No edge or surface breathers required. SILICONE PRESSURE PAD/NYLON BAG (Same as Slide 3, Works Due to Nitrogen Barrier Effect of Nylon Vac Bag) 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 @ 1 atm) Material73F125F .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

  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 BleedBleedBleedBleed Weight Before Cure, Grams 335.1 371.0 470.2 502.7 Weight After Cure, Grams 334.8*370.9469.2*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

  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 Lay-Up Mandrel Lay-Up Mandrel Lay-Up Mandrel Lay-Up Mandrel 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 4 3 Production Model in St. Louis on F-18 Panel Why It Works – Viton layer on backside of silicone

  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) • "Ultimate 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

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