230321 - Composite Materials Flashcards

1
Q

What’s the specific modulus?

A

Youngs modulus (E) divided by density (p).
Typical values for steel and iron: around 20.

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2
Q

What are the parts of a composite material?

A

Fyber reinforced plastics.
Single layers: lamina.
More layers stacked: laminate. Alternating the fibers orientation. This is the one that you actually use in production parts.

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3
Q

What types of fibers are there?

A

Glass fibers, carbon fibers, Kevlar fibers. (exceeding mechanical properties)
High stiffness in regards to its weight.
Specific modulus: 200 or so.
Not recyclable.

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4
Q

What are the two parts of the composite material?

A

Fiber and matrix. Usually the matrix has a much lower specific modulus: around 3 or 5. The matrix is usually a thermoset material. Holds the structure together, gives the distance of the fibers.

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5
Q

What is macromechanics and micromechanics?

A

MACRO: General properties of the component, mechanical average.
Micromechanics: individual behavior.

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6
Q

How the mechanical properties change in terms of the direction?

A

Higher mechanical properties in the direction of fiber, lower perpendicular .
Same with sheet metals, the rolling direction or perpendicular to it.
In a laminate, you pile several different directions, number of layers and the orientation of the layers.

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7
Q

Differents types of composite materials:

A

Parallel lines, Mesh, random fibers (glass fiber materials), particles. Best configuration is unidirectional fiber-reinforced thin layers, compared to random short fibers.

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8
Q

Natural fibers

A

Flax or jute.

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9
Q

Laminate code:

A

Square brackets […], angle orientation of the lamina in regards to the x axis [0/90-45].
If you have more layers in a given orientation, you add a subscript. [0deg/90deg]s –> symmetric
If you put a line on top of a specific value, it means that the layer is the symmetry line.

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10
Q

1D to 2D

A

rod: tensile + bending.
Plate: superposition plane elasticity and plate element.

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