Lecture 5 - Composites Flashcards
(29 cards)
What is a composite?
A material made from two or more distinct materials that are combined to create a new material with properties that are superior to those of the individual components.
What are the two main components of composites?
Matrix + reinforcement
What historical perspective is noted about gluing wood?
Gluing wood at angles produced better properties than single-ply wood.
What are examples of natural composites?
- Bone
- Wood
What are examples of synthetic composites?
- Fuselage
- Appliances and parts
- Skis
What are examples of industrial composites?
- Concrete/reinforced concrete
- Fiber-glass
- Glass reinforced aluminium
What are the classifications of composite materials?
- Particle reinforced
- Fiber reinforced
- Structural
What are the two types of particle-reinforced composites?
- Large particle
- Dispersion strengthened
What defines large particle-reinforced composites?
Large particles are used for particle-matrix interactions that cannot be treated on the atomic or molecular level.
What is the effect of large particles in a composite?
The particulate phase is harder and stiffer than the matrix, restraining movement of the matrix phase.
What is a characteristic of dispersion-strengthened composites?
Particles are normally much smaller, with diameters between 10 and 100 nm.
What do small dispersed particles do in dispersion-strengthened composites?
They hinder or impede the motion of dislocations, restricting plastic deformation.
What is specific strength?
The ratio of tensile strength to specific gravity.
What is specific modulus?
The ratio of modulus of elasticity to specific gravity.
What is critical fiber length (lc)?
The necessary length for effective strengthening and stiffening of the composite material.
What happens when fiber length (L) is equal to critical fiber length (lc)?
The maximum fiber load is achieved only at the axial center of the fiber.
What is the outcome when fiber length (L) is greater than critical fiber length (lc)?
The fiber reinforcement becomes more effective, reaching full strength over a central region.
What occurs when fiber length (L) is less than critical fiber length (lc)?
The matrix deforms around the fiber, minimizing stress transfer and providing little reinforcement.
What factors influence the mechanics of continuous and aligned fiber composites?
- Stress-strain behaviors
- Phase volume fractions
- Direction of applied stress
- Direction of applied load
What is the difference between aligned and randomly oriented discontinuous fiber composites?
Aligned composites are anisotropic, while randomly oriented composites are isotropic.
What are whiskers in fiber-reinforced composites?
Thin single crystals with high crystalline perfection and strength.
What types of matrices are used in fiber-reinforced composites?
- Polymer
- Ceramic
- Metal
What is a structural composite?
A multilayered/hierarchical and normally low-density composite used in applications requiring structural integrity.
What is a sandwich panel?
A lightweight beam or panel having relatively high stiffnesses and strengths, consisting of two outer sheets and a thicker core.
