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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.

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Presentation on theme: "Vacuum/ Vent Line TRADITIONAL NYLON VACUUM BAG WITH EDGE AND SURFACE BREATHERS Edge Sealant (Tacky Tape) Edge Breather Part Layup Mold Parting Film (FEP."— Presentation transcript:

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 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?

2 Conventional Composites Fabrication Traditional 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

3 Vacuum/ Vent Line STANDARD SILICONE RUBBER VACUUM BAG WITH EDGE AND SURFACE BREATHERS (Replace Nylon Bag and Edge Sealant With Reusable Silicone Rubber Diaphragm and Integral Seal) Rubber Edge Seal Edge Breather Part Layup Mold Parting Film (FEP or ETFE) Surface Breather Reusable Silicone Rubber Vacuum 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? Breathe Volatiles Out??? Vent Air In? Bag Frame

4 Same Bag Close-Up of Seal and Gas Springs EXAMPLE SYSTEMS OF SILICONE VAC BAGS REQUIRING BREATHERS

5 Vacuum/ Vent Line SILICONE PRESSURE PAD/NYLON BAG (FIRST PROOF OF NO-BREATHER VACUUM BAGGING CONCEPT) Edge Sealant (Tacky Tape) Edge Breather Eliminated Part Layup Mold Parting Film (FEP or ETFE) Silicone Rubber Pressure Pad (Surface Breather Eliminated) Nylon Vacuum Bag Silicone Rubber Pressure Pad Substituted for Breather Material. Parts Came Out Looking Beautiful. No Breathers Used. Why Does It Work? Breathe Volatiles Out??? Vent Air In? 1 2 Probe Pad

6 Vacuum/ Vent Line STANDARD SILICONE RUBBER DIAPHRAGM, NO BREATHERS (Does Not Produce Good Parts – WHY?????????) Rubber Edge Seal Part Layup Mold Parting Film (FEP or ETFE) Reusable Silicone Rubber Vacuum Bag Bag Frame Now We Switched to Standard Silicone Rubber Vacuum Bag Over FEP – No Breather Part Showed Horrible Porosity Probe Pad

7 Vacuum/ Vent Line STANDARD SILICONE RUBBER DIAPHRAGM, NO BREATHERS (Does Not Produce Good Parts Without Nitrogen Barrier Layer) Rubber Edge Seal Part Layup Mold Parting Film (FEP or ETFE) Reusable Silicone Rubber Vacuum Bag Bag Frame Why A Standard Silicone Rubber Vacuum Bag Over FEP Does Not Work: Autoclave Nitrogen Permeates Through Silicone, Through FEP, And Into Part, Causing Porosity AUTOCLAVE ATMOSPHERE (Nitrogen, 350F, 45 Psi)

8 Vacuum/ Vent Line SILICONE PRESSURE PAD/NYLON BAG (Same as Slide 3, Works Due to Nitrogen Barrier Effect of Nylon Vac Bag) Edge Sealant (Tacky Tape) Edge Breather Eliminated Part Layup Mold Parting Film (FEP or ETFE) Silicone Rubber Pressure Pad (No Surface Breather) Nylon Vacuum Bag Nylon bag acts as gas barrier layer. Pressure pad provides superior bagside surface. No edge or surface breathers required. 1 2 Probe Pad AUTOCLAVE ATMOSPHERE

9 Vacuum/ Vent Line SILICONE/VITON DIAPHRAGM, NO BREATHERS (No Breathers – Viton Layer is a Barrier Within a Reusable Vacuum Bag System) Rubber Edge Seal Part Layup Mold Parting Film (FEP or ETFE) Silicone/Viton Vacuum Bag (Black Outer Layer Is Viton) Bag Frame Viton Layer Outside Silicone Diaphragm Acts As A Barrier, Preventing Autoclave Nitrogen From Reaching Part and Causing Porosity AUTOCLAVE ATMOSPHERE

10 ASTM D1434 NITROGEN GAS PERMEABILITY (cc/m 2 1 atm) Material73F125F.004" Nylon Bagging Film " Nylon Bagging Film< " White Tedlar " FEP Release Film " Silicone Rubber " Silicone Rubber " Viton Fluoroelastomer15151

11 8-256,8-256,8-168,8-168, No Edgew/ EdgeNo Edgew/ Edge BleedBleedBleedBleed Weight Before Cure, Grams Weight After Cure, Grams334.8* *503.0 Percent Weight Loss0.09%*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 and 11-ply 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:

12 "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

13 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) 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 Vacuum Probes Not Shown

14 Silicone/Viton - Optimum Material, Labor Reduction 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 Why It Works – Viton layer on backside of siliconeProduction 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) "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) Vacuum/ Vent Line The Ultimate Answer: An impermeable release film that could be simply placed under existing silicone rubber diaphragms, eliminating need for breathers Impermeable release film acts as nitrogen barrier (same effect as Viton)


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