How is the young's modulus of a composite determined?
By predicting upper and lower bounds of E in two conditions: uniform strain and uniform stress.
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What is 'axial stiffness'?
Predicts the stiffness of an aligned commposite along its axis. Model: fibres are considered to be considerably long,approximated by two slabs of material bonded together at an interface.When deformed in axial direction the two slabs have same strain
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What is transverse stiffness?
Slab is subjected to a stress in the x_2 direction (tensile stress perp to axial)
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Why is the analysis of transverse properties less accurate than of axial properties?
For transverse:Strains in matrix are not uniform, and matrix can be constrained from deforming by the presence of high-modulus fibres. So transverse stiffness is the lower bound.
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Why do we laminate a composite?
If aligned composites can be countered by stacking laminae consisting of oriented fibres, together differently to form a laminae.
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What is 'Laminate theory'?
Mechanical properties of the laminae can be determined, each layer us an aligned composite and treated mathematically as an orthotropic elastic material in state of plane stress.Assumed: layers posses four elastic constants.Stress through thickness=0
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Describe an 'orthotropic elastic material'
A material that have properties which differ along three mutually orthogonal twofold axes of rotational symmetry.
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What is the significance of woven fibres?
They can reduce delamination (with some reduction in in-plane properties).
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Define Delamination
Mode of failure where layers separate forming mica like structure of separate layers with a significant loss of mechanical toughness.
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How can composites be characterised?
Visual inspection:optical microscopy,SEM,TEM(nano-particles), XCT-> obtain 3D images of composite microstructure
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Other cards in this set
Card 2
Front
What is 'axial stiffness'?
Back
Predicts the stiffness of an aligned commposite along its axis. Model: fibres are considered to be considerably long,approximated by two slabs of material bonded together at an interface.When deformed in axial direction the two slabs have same strain
Card 3
Front
What is transverse stiffness?
Back
Card 4
Front
Why is the analysis of transverse properties less accurate than of axial properties?
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