Composites

Composites

1. Constructions methods

   • Solid laminate
     • Fuselage made mostly from BMS 8-276 carbon tape
   • Honeycomb
     • Usually made from aramid paper
     • Hexagonal, flexicore, overexpanded and bisected core

2. Materials

   • Fibers
     • Carbon
     • Aramid (Kevlar)
       • Water absorption, tigh
     • Glass
     • Products
       • Fabric
         • 3K-70-PW as example, or 6K -70-PW-PB4 for IWWF
       • Tape
         • Grade 95, 145 or 190, weight per square meter
   • Thermosetting Resins
     • Epoxy
       • 250F & 350F, strongest and most durable
         • Refrigerantion is required
           • Mechanical life time at room temperature when cure is initiated
           • Handling life is max time allowed at room temperature
       • Resin and hardener
         • Exothermic cure
         • Wet layup
           • BMS8-201 for sealing
           • BMS8-301 for wet layout repairs
         • Pre preg
           • BMS 8-276 most common use resin at B787
       • Glass transition temperature
         • Thermosetting plastics do not melt at high temperature, undergo a glass transition and get soft
         • If temperature is over Tg the ressistance decreases, moisture decreases Tg
     • Phenolic / Polyester
       • Interior components
     • State
       • A: Not mixed, typically for wet layup repairs
       • B: Mixed, chemical reaction has starded. Typically for wet layup
       • C: Cured
   • Potting compound
     • Resin mixed with filler, for edges, reinforce, etc. commonly BMS5-28
   • Paste adhesives
     • Usually used to bond cured parts
   • Film adhesives
     • Thin sheets of epoxy stage B
   • Foaming Adhesive
     • B staged epoxy, they expand during curing cycle
   • Non continuous reinforcements
     • Miller fibers
     • Particles
     • Whiskers

3. Repair

   • Vacuum bag assembly
     • -Perforated parting film
     • Bleeder
     • Solid parting film
     • Caul plate
     • Breather
     • Vacuum bag
     • Sealing compound
     • Thermocouples Tipe J
       • Two layers of Temp tape if installed over caul plate
     • Hot bonder
     • Heating devices
       • Heat blanket
         • Edges of the repair and thermocouples must be at least 2in from heat blanket edge
       • Autoclave
       • Oven
       • Heat lamps
       • Hot air blowers
   • Resin
     • Resin must be mixed by 1,3 per weight of the febric for CFRP, 1 for GFRP
     • Mixed slowly for 2 minutes
   • Cure cycle
     • heat up
     • Dwell
     • Cool down
     • Heat transfer in repairs
       • Conduction
       • Convection
       • Radiation
     • Max loss of vacuum is 5in of mercury every 5 minutes
   • Wet layup
   • Prepreg
     • DVD if the repair is for more than 6 plies

4. Inspection

   • Tap test only relaiable for 3 plies or less
   • DVI
   • GVI