1ENG 4793: Composite Materials and Processes1Vacuum Bagging /Autoclavever 1ENG 4793: Composite Materials and Processes2Autoclave Process SequenceHigh Performance Parts• Prepare plies• Stack plies in tool• Add dry material to absorb excess resin &remove volatiles• Apply vacuum bag & cure in autoclave• Oven postcure for environmental durability•Trim• Inspect• AssembleENG 4793: Composite Materials and Processes3Hand lay-up shopENG 4793: Composite Materials and Processes4Vacuum Bag AssemblyENG 4793: Composite Materials and Processes5Vacuum bagENG 4793: Composite Materials and Processes6Lay-upMaterial on stiffeningstructureVacuum bag andfittings attached2ENG 4793: Composite Materials and Processes7Alternate Resin Bleed PathsENG 4793: Composite Materials and Processes8Release Materials• Common Materials:– Fiberglass:• Coated with Teflon• Coated with Mold Release–Nylon– Polyester–FilmENG 4793: Composite Materials and Processes9Breather Material• Common Materials– Fiberglass– Polyester Felt– Cotton• Limitations–Pressure– Temperature• Failure Modes– Inadequate Testing– QualityENG 4793: Composite Materials and Processes10Sealant Tape• Major Manufacturers– Schnee-Morehead– General Sealants• Limitations–Tack– Temperature• Failure Methods– Release–FlowENG 4793: Composite Materials and Processes11Nylon Films• Manufacturing Methods–Cast–Blown• Film Types and Properties– Resin Types - 6 - 66 - 666– Sheets, Tubes, & Bags• Limitations• Failure MethodsENG 4793: Composite Materials and Processes12Vacuum Bagging Problems• Labor Intensive• Inconsistent Performance• Trapped Air/Volatiles• Controlling Bleed• Poor Heat Transfer• Consumes Expensive Materials•Wrinkles• Loss of Seal• Inadequate Pressure Transmission3ENG 4793: Composite Materials and Processes13Use of Rubber Pad to Prevent BridgingENG 4793: Composite Materials and Processes14AutoclaveENG 4793: Composite Materials and Processes15AutoclaveENG 4793: Composite Materials and Processes16Autoclave Features•Gases– Air (If T < 150oC)–N2 (most common)–CO2 (if P < 300 psig)• Heating– Electric (if small)– Indirect gas fired (iflarge)– Integrally heatedtooling (recently)• Gas Circulation– Needed for heattransfer– Velocity = 1 to 3 m/s•Vacuum– One outlet per 2.5 ft3of bag area– Trap volatiles (maybe toxic)– Control internal bagpressure (hard!)ENG 4793: Composite Materials and Processes17Epoxy Autoclave Cure Cycle• Apply vacuum inside bag at 20-30” Hg (70-100 kPa• Apply autoclave pressure at 85 + 5 psi (585 + 35 kPa• Heat slowly to 250 + 10oF (120 + 5oC) at 3 to 5oF/min (2 to3oC/min)• Hold at T and P 60 to 70 min• Raise P to 100 + 5 psi (690 + 35 kPa)• Release vacuum• Raise T to 350 + 10oF (177 + 5oC) at 3 to 5oF/min (2 to3oC/min)• Hold at T and P 120 + 10 min• Cool slowly to below 100oF (40oC) at 5oF/min (3oC/min)• Release autoclave pressureENG 4793: Composite Materials and Processes18Alternative Curve Cycle for V-378A4ENG 4793: Composite Materials and Processes19Large Autoclave ExampleENG 4793: Composite Materials and Processes20 Autoclave Curing Evaluation• Investment– Autoclave systemexpensive– Modest tooling• Materials– Thermoset advancedcomposites tailored forautoclaves• Products– Low volume– Moderate areas (someexceptions)– Complex shapes– High cost• Processing–Slow– Low Labor (excludingpreparation)– Remote Hazards• Quality– Low defects– High properties– Fair consistencyENG 4793: Composite Materials and