Composite Processing ISAT 430 Module 4b

ISAT 430 Module 4a Dr. Ken Lewis Spring Polymer Based Composites Preforms Powders or granules of polymer are mixed and preheated BMC bulk molded compounds SMC sheet molded compounds Pre-combined sheets of resin, reinforcement, filler, and fabrics with an upper and lower carrier film

ISAT 430 Module 4a Dr. Ken Lewis Spring Thick Molding Compound

ISAT 430 Module 4a Dr. Ken Lewis Spring Fiber composition The strongest composites are made from continuous filaments May be gathered in bundles May be woven into various cloth or tape orientations Carbon fiber is available in lengths of up to 13,000m in bundles of 1,000 – 160,000 filaments of 7.5 micrometers in diameter.

ISAT 430 Module 4a Dr. Ken Lewis Spring Fiber composition Roving Continuous filaments in strands or yarns Chopped strands Cut from roving in lengths of 3 to 50 mm Woven roving and tapes

ISAT 430 Module 4a Dr. Ken Lewis Spring Woven & Knitted Roving

ISAT 430 Module 4a Dr. Ken Lewis Spring Tapes

ISAT 430 Module 4a Dr. Ken Lewis Spring Hand Lay-up & Spray –up Molding One sided male or female form is used. A surface skin layer called the ‘gel coat’ is first applied Usually the material cures at room temperature Sometimes a radiant surface heater may be used.

ISAT 430 Module 4a Dr. Ken Lewis Spring Hand Lay-up & Spray –up Molding Used for large items Large boats Swimming pools Shower stalls Septic tanks Polyesters and epoxies are used in the gel coating (smooth finish)

ISAT 430 Module 4a Dr. Ken Lewis Spring Hand Lay-up & Spray –up Molding Resin may be mixed in a bucket Applied using a brush, squeegee, roller etc.

ISAT 430 Module 4a Dr. Ken Lewis Spring Filament Winding Very sophisticated technique Spherical, cylindrical, other shapes Winding a continuous filament in a pre-designed pattern and under constant tension onto a mandrel. Computer Numerical Control (CNC) machine with up to 7 degrees of freedom Two alternative ways of winding Wet – filament and resin are applied separately and simultaneously Dry – pre-preg tapes are used A mandrel is a tapered or cylindrical axle in the shape of the piece being formed. it serves as a support.

ISAT 430 Module 4a Dr. Ken Lewis Spring Filament winding Can orient the fibers in the direction of maximum expected stress. A) helical winding B) polar winding C) hoop winding Axis Of rotation

ISAT 430 Module 4a Dr. Ken Lewis Spring Mandrels The filament wound shell is produced over a mandrel After the shell is finished, most mandrels are intended to be washed out, melted out, broken out or collapsed Mandrel constructions are of wood, cardboard, plaster, and low melting plastics.

ISAT 430 Module 4a Dr. Ken Lewis Spring Filament Winding Kinematics The helical winder The normal axial winder The braid wrap winder

ISAT 430 Module 4a Dr. Ken Lewis Spring Multi-coordinate NC tape laying machine. Seven numerically controlled axes Rotation of the mandrel (C) Longitudinal travel (Z) Head yaw (I) Head pitch (J) Head roll (K) Arm tilt (Y) Arm crossfeed (X) Two motions to restart the tow Redirect roller angular position Tow restart linear position.

ISAT 430 Module 4a Dr. Ken Lewis Spring Multi-coordinate NC tape laying machine.

ISAT 430 Module 4a Dr. Ken Lewis Spring Filament placement head Up to 24 tows (each 3.18 mm wide) are collimated into a fiber band Fiber band is applied to the part with a compaction roller It is heated with a stream of hot air to achieve the right plasticity.

ISAT 430 Module 4a Dr. Ken Lewis Spring Raytheon Aircraft Premier I

ISAT 430 Module 4a Dr. Ken Lewis Spring Pultrusion Method Fibers are impregnated with polymer Positioned with guides Preheated Pulled through a tapered die or guide Then either cut or wound up.

ISAT 430 Module 4a Dr. Ken Lewis Spring Pultrusion

ISAT 430 Module 4a Dr. Ken Lewis Spring Pultrusion Used for two dimensional shapes; Solid rods Hollow tubes (Similar to extrusion) Uses Golf club shafts Drive shafts Ladders Walkways and handrails

ISAT 430 Module 4a Dr. Ken Lewis Spring Metal Matrix Composites Filler is either ceramic particulates or various ceramic fibers. The first are called “cermets” Ceramics can dominate the mix Two types Cemented carbides WC – Co TiC – Co TiC -- Ni Oxide – based cermets

ISAT 430 Module 4a Dr. Ken Lewis Spring MMC Preparation Cemented carbides Similar to powder metallurgy Mixing Compaction sintering

ISAT 430 Module 4a Dr. Ken Lewis Spring Mixing Powders of carbide and the binder metal are ground to the correct size Mixed wet in a ball mill (a ball mill is essentially a jar with hard marbles in it) Process makes the particle size more uniform End up with a uniform sludge Dried in a controlled atmosphere to prevent oxidation

ISAT 430 Module 4a Dr. Ken Lewis Spring Compaction Cold pressing Dies are made oversize to allow for shrinkage upon sintering. Shrinkage can be 20% or more For high production rates, the dies have WC—Co liners to reduce wear For low production rates, large flat sections are made and and specified shapes cut from the sheets.

ISAT 430 Module 4a Dr. Ken Lewis Spring Sintering Allows the metal particles to bond The part is heated to 0.7 – 0.9 of the metals melting point and held. Driving force is a reduction in surface energy For WC – Co the temperature is around 2550°F (1400°C) Some WC dissolves into the Co As the WC dissolves, the melting point is lowered and finally melting occurs

ISAT 430 Module 4a Dr. Ken Lewis Spring Finishing Essentially grinding with a diamond or other hard abrasive to final net shape Major uses Cutting tools Drill bits Deep hole drilling