Sniffer Port Assembly in Vacuum Bagging

Sniffer Port

• A two-part valve system consisting of a base plate and a valve section that screws into it
• The base plate is made from aluminum or heat-resistant plastic and has a rubber seal to ensure an airtight seal on the vacuum bag
• The valve section allows the vacuum supply to be disconnected from the lay-up without losing vacuum from the bag
• Useful for checking the bag for leaks before the cure cycle starts

Vacuum Hoses

• Different types of hoses are used depending on the curing method (oven, autoclave, heat blankets, heat guns, or lamps)
• Hoses must be heat-resistant if they are enclosed in the heating environment
• Plastic hoses can be used with an internal wire to prevent collapsing if they are not in a heating environment

Curing of Composite Materials

• Composite matrix systems cure through chemical reaction
• Some systems cure at room temperature, but heat can accelerate the process
• Two-part epoxy resin systems are typical of room-temperature curing systems
• Large manufacturing facilities have the necessary equipment to repair large damaged surfaces
• Autoclaves are used to cure composite materials at high heat and pressure

Hot Patch Bonding Equipment

• Hot patch bonding machines perform two functions: applying atmospheric pressure and heat
• Heat blankets with electrical coils are used to heat up quickly
• Temperature control is critical to achieve effective results
• Controllers are used to slowly raise the temperature, hold it constant, and then slowly decline
• Recording the temperatures of the curing process is important

Repair Environment

• Most adhesives and resins absorb atmospheric moisture, which can cause void formation during elevated temperature cure
• Moisture degrades the elevated temperature properties of adhesives and resin systems
• Repairs should be performed in a controlled area to reduce contamination and prevent degradation
• The atmosphere in the controlled area must have regulated temperature and humidity within prescribed limits

Controlled Areas

• Adhesive bonding and composite fabrication must be performed in a controlled area with a Preparation Room and a Bonding Room
• Access should be restricted to essential personnel only
• The Preparation Room must be reserved exclusively for adhesive bonding purposes
• The Bonding Room must be separate from the Preparation Room

Storage Areas

• Provision should be made for storage of composite and adhesive bonding materials and components awaiting repair
• Store resins, solvents, catalysts, and accelerators in original containers or in clearly labeled containers
• Store these materials in flame-proof approved cabinets when not in use
• Ensure lids are securely fitted when not in use, and do not inter-mix resin and hardener batch/lot numbers

Counterbores

• Counterbores can be used with all types of composite materials except aramid, as this may create excessive fuzzing

Safety Equipment

• Dust masks or respirators with fine filters are required when sanding, drilling, or trimming some composite structures
• A dust collector or downdraft table is desirable to use while sanding to pull the fine particles out of the air
• Eye protection is necessary when working with chemicals or power tools

Quality Assurance Methods

• There are currently no methods of establishing the strength and durability of a given composite repair without destroying the repair
• Methods of establishing that the cured resin matrix should perform as designed include lap shear testing and Barcol hardness testing