Chapter 16 Flashcards
What is a composite?
- A combination of two or more individual materials
- Multiphase material that is artificially made
What are the two different phase types?
- Matrix
- Dispersed
What is the matrix phase type?
The continuous phase that surrounds the dispersed phase
What is the dispersed phase type?
Discontinuous phase and is surrounded by the matrix phase
What is the purpose of the matrix phase?
- Transfer stress to the dispersed phase
- Protect the dispersed phase from the environment
What are the main types of composites?
- MMC (metal matrix composite)
- CMC (ceramic matrix composite)
- PMC (polymer matrix composite)
What is the goal of composites?
To obtain a more desirable combination of properties
What are the types of dispersed phases?
- Particle
- Fiber
- Structural
What is the purpose of a dispersed phase in an MMC?
To increase yield strength, tensile strength, and creep resistance
What is the purpose of a dispersed phase in a CMC?
To increase fracture toughness
What is the purpose of a dispersed phase in a PMC?
Increase Young’s Modulus (stiffness), yield strength, tensile strength, and creep resistance
What are the four main classes of composites?
- Particle-reinforced
- Fiber-reinforced
- Structural
- Nano
What are the two types of particle-reinforced composites?
- Large-particle
- Dispersion-strengthened
What are the two types of fiber-reinforced composites?
- Continuous (aligned)
- Discontinuous (short)
> Aligned or randomly oriented
What are the two types of structural composites?
- Laminates
- Sandwich panels
What are some examples of particle-reinforced composites?
- Spheroidte steel
> Ferrite matrix (ductile) & cementite (brittle) - WC/Co cemented carbide
> Cobalt matrix (ductile, tough) & WC (brittle, hard) - Automobile tire rubber
> Rubber matrix (compliant) & carbon black (stiff) - Concrete
What is the composition of concrete?
- Gravel
- Sand
> Sand fills the voids between gravel - Cement
- Water
What are the types of concrete treatments?
- Reinforcing
- Prestressing
- Posttensioning
What is reinforced concrete?
- Concrete reinforced with steel rebar or remesh
- Increases strength, even if concrete matrix cracks
What is prestressed concrete?
- Rebar/remesh is placed under tension during setting
- Tension is released after setting which places concrete in compression
- To fracture, tensile stress must exceed the compressive stress
What is posttensioned concrete?
- Nuts are placed on ends of rebar
- Tightened to place concrete under compression
What is the rule of mixtures?
- The properties of a composite are based on an average of the properties of the constituents
- Often based on volume
What is dispersion strengthening?
- Dispersing very small particles of a hard, inert phase within a load-bearing matrix phase
- Particles hinder displacement motion
What is large-particle strengthening?
- Larger particles are placed within a matrix
- Matrix transfers stresses to particles