Composite Materials: Manufacturing Methods and Selection Criteria

Composite Materials

Selection Criteria of the Method to Use

1. Specified technology
2. Production parameters

Cost per Piece

• Preparation and setup time
• Tooling needs, equipment, and human resources
• Production rates
• Material cost
• Size range

Ranking Methods

Contact Molding

Molded fiber-matrix (of the piece). Starting material:

1. In situ dry fiber impregnated with resin. Wet process.
2. Fiber resin impregnated with cure retardant.

Prepregs: Mat and mixed. 70% fiber, guidance! Cut pollution, not very expensive, 10 layers, vacuum autoclave, existing alternatives.

Variants

(Increase production rates when structural requirements are not high):

1. Projection Method: Mix by air pressure. Reduces production time by 30%.

2. Centrifuge Method: The projection of the mixing is done inside a rotating tube mold.

Compression Molding

Reinforcement and resin between mold and press counter-mold closed.

Variations

1. Cold Compression: Cured at room temperature in minutes. Reinforcement in the form of felt. Worse structural capacity.

2. Hot Compression: Heated molds. Faster curing. Reinforcement: compound. This can be obtained according to good properties and characteristics, but not structural.

Pultrusion

Rods. Explain the system, coil heated and traced, mechanical characteristics. Large series.

Filament Winding

Or alpha, temperature, mandrel (3), then autoclave. These can be structural.

Injection Molding

1. Dry fiber mold closes and catalyzed resin is injected.
2. The closed mold is injected with a composite of fiber and resin.

Types

1. Resin Injection Molding (RIM)
2. Injection of compound in privileged directions.

3. Resin Transfer Molding (RTM). 3D x 3D. Epoxy, carbon fiber.

   Process: Preform 3D, mold, resin injection, vacuum cured.

   Elements:

   1. Preform: Filling critical, solutions.

   2. Resin

   3. Mold: Metal stamping, entrances and exits, heating, demolding.

   4. Transfer: Injection (1 bar), soaking, leftovers, cured, with overpressure (6 bar), vacuum (5 mbar).

Prepregs vs. RTM Comparison

Structural parts (3D vs. layers), cost, faces, sets.

Process Parameters

1) Production

• Equipment cost
• Tooling cost
• Material cost
• Production speed
• Production times and setup
• Manpower

2) Technology

• Fiber volume (70%)
• Pore volume (1%)
• Fiber orientation (satin 5, taffeta, and high resistance)
• Dimensions and geometry
• Dimensional tolerances
• Surface finish
• Ability to insert into the piece
• Emission of gases