Composite Materials Flashcards
What are Composite Materials?
Composite materials are material systems made from two or more physically distinct phases.
These phases combine to create properties that are different from the individual components.
They are often stronger, lighter, or more durable than their individual parts
Examples of composite materials
Cemented carbide (WC with Co binder): Used for cutting tools due to its hardness (tungsten carbide) and toughness (cobalt binder).
Plastic molding compounds with fillers: Fillers like clay or wood flour can improve strength or reduce cost without compromising overall properties.
Rubber mixed with carbon black: Carbon black strengthens rubber and improves its elasticity, making it ideal for tires.
Wood: A natural composite where cellulose fibers provide strength and lignin acts as a binder.
Matrix
Term: Matrix
Description:
Continuous phase in a composite material.
Surrounds and binds the filler together.
Usually ductile, tough, and has a lower density than the filler.
Strength is typically lower than the filler.
Examples:
Thermoplastics (e.g., polyethylene, nylon)
Thermosets (e.g., epoxy, phenolic)
Filler
Term: Filler / Reinforcing Material
Description:
Dispersed phase in a composite material.
Often strong and stiff, with a low density.
Designed to improve the overall properties of the composite.
Examples:
Fibers: glass, carbon, aramid (Kevlar)
Particles: clay, wood flour, metal oxides
Matrix and Filler Interaction
The bond between the matrix and the filler is crucial for the performance of the composite.
A good interface transfers stress effectively between the two phases.
Bonding can be adhesive (chemical) or mechanical.
Benefits of Composites
Term: Composite Advantages
Description:
By combining materials, composites can achieve properties not possible with individual components.
Benefits include:
High strength-to-weight ratio
Improved stiffness and rigidity
Design flexibility
Corrosion resistance
Example - Fiberglass
Material: Fiberglass
Matrix: Polymer (e.g., epoxy)
Filler: Glass fibers
Properties: Strong, lightweight, good corrosion resistance
Advantages of Composites
High Strength-to-Weight Ratio
High Specific Strength
High Creep Resistance
High Tensile Strength at Elevated Temperatures
Improved Performance under Cyclic Loads
Impact Resistance and Damping
High Wear Resistance
Corrosion Resistance
Reduced Dimensional Changes with Temperature
Anisotropic Properties
Disadvantages (or limitations) of Composites
Material Costs: Raw materials for composites can be expensive compared to some metals.
Fabrication Difficulties: Manufacturing processes for composites can be complex and require specialized equipment, increasing production costs.
Repair Challenges: Repairing composite components can be more challenging and expensive compared to metals.
Statistical Variability: Properties of composites can exhibit some variation due to the manufacturing process, requiring careful quality control.
Temperature Limitations: Polymeric matrix composites typically have lower operational temperature limits compared to metal matrix composites.
Design Complexity: The anisotropic nature of composites requires careful design considerations to account for the directional properties.
Inspection and Testing: Inspecting and testing composites for damage or defects can be more complex compared to traditional methods used for metals.
Metal Matrix Composites (MMC)
Matrix: Metal (aluminum, magnesium, iron, cobalt, copper)
Reinforcement: Ceramic (oxides, carbides) or Metallic (lead, tungsten, molybdenum)
Examples: Al-SiC (silicon carbide), Al-Al2O3 (aluminum oxide)
Properties:
High strength
High stiffness
Abrasion resistance
Dimensional stability
High-temperature performance
Improved toughness (compared to pure metals)
Ceramic Matrix Composites (CMC)
Matrix: Ceramic
Reinforcement: Ceramic fibers
Example: Silicon carbide-silicon carbide (SiC-SiC)
Properties:
Excellent high-temperature performance
High wear resistance
High hardness
Brittleness (can be a limitation)
Polymer Matrix Composites (PMC)
Matrix: Polymer (thermoset or thermoplastic)
Thermoset: Epoxy, Unsaturated Polyester (UP)
Thermoplastic: Polycarbonate (PC), Polyvinylchloride (PVC), Nylon, Polystyrene
Reinforcement: Fibers (glass, carbon, steel, Kevlar)
Examples:
GFRP (fiberglass): Polyester or epoxy with glass fibers
CFRP: Polyester or epoxy with carbon fibers
KFRP: Polyester or epoxy with Kevlar fibers
Properties:
High strength-to-weight ratio
Good corrosion resistance
Design flexibility
Can be tailored for specific properties based on fiber type
Composites in Engineering Applications
Widespread Use: Composites are finding increasing use in various engineering applications due to their unique properties.
Applications in Specific Industries
Aerospace: Because of their high strength-to-weight ratio, composites are ideal for aircraft components like wings, fuselages, and control surfaces. This translates to lighter airplanes with improved fuel efficiency and performance.
Automotive: Composites are used in car bodies, hoods, spoilers, and other parts to reduce weight and improve fuel economy. They can also be used for high-performance components requiring strength and stiffness.
Pressure Vessels and Pipes: Composites offer superior corrosion resistance and can be lighter than traditional materials like steel, making them suitable for pipelines and pressure vessels in various industries.
What are Biomaterials?
Definition 1 (Hench & Erthridge, 1982): Materials used to create medical devices that replace or restore a bodily function in a safe, reliable, and cost-effective way, with minimal impact on the body.
Definition 2 (Bruck, 1980): Materials, both natural and synthetic, that come into contact with living tissues, blood, or fluids for prosthetic, diagnostic, therapeutic, or storage purposes. They should not negatively affect the body or its components.
Definition 3 (Williams, 1987): Non-living materials used in medical devices that interact with biological systems within the body.
