What are the types of composite materials? General information about the cutting tools and cutting angles used in the machining of these materials.

Types of Composite Materials

Composite materials consist of two main components:

Reinforcement material (fiber, particle, etc.) increases strength and stiffness.

Matrix material (polymer, metal or ceramic) holds the reinforcement elements together.

1. Fiber-Reinforced Composites

These composites are structures where fibers are embedded in the matrix.

Glass Fiber Reinforced Plastic (GFRP): Polymer matrix reinforced with glass fiber.

Carbon Fiber Reinforced Plastic (CFRP): Provides high strength and lightness.

Aramid Fiber Reinforced Plastic (AFRP): Offers high impact resistance (e.g. Kevlar).

2. Particle Reinforced Composites

Contains particles dispersed in the matrix.

Metal Matrix Composites (MMC): Ceramic particle (e.g. Aluminum-SiC) with a metal matrix.

Ceramic Matrix Composites (CMC): Ceramic matrix with particles (e.g. Alumina-Zirconia).

3. Layered Composites

Laminated Composites: Fiber layers placed in different directions.

Sandwich Structured Composites: Combination of lightweight core material and outer surfaces.

4. Natural Fiber Reinforced Composites

Biopolymer matrices and natural fibers such as flax and hemp are used.

Machining of Composite Materials

During the processing of composite materials, special approaches are required due to the mechanical properties of different fiber and matrix components. Difficulties such as delamination, fiber pullout, matrix cracking may be experienced during machining.

Cutting Tools

Cutting tools used for composite materials are generally developed with wear-resistant and special coatings.

1. Carbide Cutting Tools

Coated Carbide: Offers hard wear resistance (e.g. TiAlN, TiCN coating).

It is frequently used in composites containing glass and carbon fiber.

2. Polycrystalline Diamond (PCD) Tools

It is especially preferred in hard composites such as CFRP and MMC.

It provides low tool wear and superior surface quality.

3. Diamond Coated Cutters

Provides long tool life in extremely hard and abrasive materials.

It is high cost but suitable for precision machining requirements.

4. Ceramic Tools

It is suitable for high temperature composites such as MMC and CMC.

It can be used at high speeds.

Cutting Angles and Geometries

Cutting angles and tool geometries are critical in the machining of composites:

1. Positive Rake Angle

Small Positive Rake Angle (+6° to +15°): Minimizes matrix deformation and fiber pullout.

2. Cutting Angle and Chip Breakers

Cutting Tip Geometry: Sharp tips prevent matrix cracking and fiber breakage.

Chip Breakers: Used for shorter chip formation.

3. Depth of Cut

Low Depth of Cut: Preferred to prevent damage to fibers.

4. Cutting Edge Rounding

Sharp Edge: Allows fibers to be cut without breaking.

Rounded Edge: Used in hard composites.

5. Helical Geometry

Helical Tools: Prevent delamination, reduce cutting forces.

Machining Parameters

The following parameters should be considered during composite machining:

Cutting Speed: Medium-high speeds are used depending on the type of composite.

CFRP: 200–400 m/min.

GFRP: 150–250 m/min.

Feed Rate:

Low feed (0.05–0.2 mm/dt) if high surface quality is desired.

Cooling:

Generally dry cutting: Preferred to prevent matrix deformation.

Conclusion

Choosing the right tool, optimum cutting angle and using appropriate parameters in the processing of composite materials reduces problems such as delamination, wear and cracks.

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