230321 - Composite Materials Flashcards
What’s the specific modulus?
Youngs modulus (E) divided by density (p).
Typical values for steel and iron: around 20.
What are the parts of a composite material?
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.
What types of fibers are there?
Glass fibers, carbon fibers, Kevlar fibers. (exceeding mechanical properties)
High stiffness in regards to its weight.
Specific modulus: 200 or so.
Not recyclable.
What are the two parts of the composite material?
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.
What is macromechanics and micromechanics?
MACRO: General properties of the component, mechanical average.
Micromechanics: individual behavior.
How the mechanical properties change in terms of the direction?
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.
Differents types of composite materials:
Parallel lines, Mesh, random fibers (glass fiber materials), particles. Best configuration is unidirectional fiber-reinforced thin layers, compared to random short fibers.
Natural fibers
Flax or jute.
Laminate code:
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.
1D to 2D
rod: tensile + bending.
Plate: superposition plane elasticity and plate element.
