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Principles of Composites (L2)
Composites Lecture 2
32
Engineering
Undergraduate 4
09/19/2011

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Term
What is the definition of a composite?
Definition
A material that constitutes of two or more phases being a matrix and reinforcement
Term
What are the types of reinforcement?
Definition
Particulate, short fiber, long fiber
Term
Particulate Composite
Definition
may be of fixed or random size and shape. low aspect ratio
Term
Discontinous Fiber
Definition
high aspect ratio of fibers. Can be fixed lengths, and direction, or random.
Term
Continous fiber. What are the types?
Definition
Fibers span large distances. Multidirectional or undirectional.

orientations: undirectional, biaxial, triaxial
Term
What are common Matrix materals?
Definition
Polymers: epoxy, polyester, nylon,
ceramics
metals
Term
What are common reinforcements?
Definition
Fibers: glass, carbon, kevlar, basalt,
Particulates: carbon, aluminium, sillica etc
Term
What is a thermoplastic matrix?
Definition
Linear or branched chains held together by crystallinity.
Term
What is a thermoset matrix?
Definition
Crosslinked chains, ideally forming a single molecule
Term
What are particulate reinforcements used for? What purpose do they serve?
Definition
Additives
modify physical, chemical, or mechanical properties
Term
Examples of particulate reinforcements. what properties does each add to composite?
Definition
-nano-clay (mechanical/physical)
-metallic particles (electrical, thermal, magnetic)
-elastomer (toughness)
-metallic nano-particles (thermal expansion)
Term
Nano: What does Agglomeration refer to?
Definition
atraction between nano particles
Term
Nano: What does intercalation refer to?
Definition
partial separation of nano particles
Term
Nano: What does exfoliation refer to?
Definition
complete separation of nano-particles from one another
Term
Nano: What does dispersion refer to?
Definition
consistent distribution of polymers throughout the polymer matrix
Term
What properties does fiber reinforcement add to material?
Definition
-smaller defect treshhold
-greater bending limit
-polymer chain alignment
Term
What purpose does the matrix add to fibers?
Definition
it connects the fibers and help distribute load across many fibers
Term
What is discontinous fiber refered to as?
Definition
reinforced plastics. Have a critical minimum length
Term
Continous fiber
Definition
Adds greatest contribution of properties
Term
Properties of composites?
Definition
Engineered materials leveraging properties of constituent materials while mitigating the disadvantages
Term
Describe homogenity of composite materials
Definition
homogenity on large scale while hetero on small scale
Term
describe isotropic, anistropic, and orthotropic materials
Definition
iso: identical properties in any direction
-aniso: several
-ortho: 3 perpendicular planes of symatry
Term
Composite products?
Definition
solids, shells, sandwish structures
Term
Composite products?
Definition
solids, shells, sandwish structures
Term
What are the 3 main composite processing teqniques?
Definition
wet layup, prepreg, infusion molding
Term
Different Infusion molding teqniques?
Definition
RTM, LRTM, VARTM
Term
What does RTM stand for?
Definition
Resin Transfer molding
Term
What does RTM stand for?
Definition
Resin Transfer molding
Term
Esplain the VARTM process
Definition
-single sided mold is filled with reinforcement
-flow aiding media is added above reinforcement
-plastic film is sealed to edges of mold
-air is vacumed out of the mold
-matrix resin is drawn in by vacuum
Term
What does the rule of mixture say? (formula)
Definition
xc=(xf)(vf)+(xm)(vm)

v is rel volume to total
Term
What type of composite process is best for the marine industry?
Definition
Wet layup
Term
What type of composite process is best for the aerospace industry?
Definition
prepreg/autoclave
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