Categories of loading
- Compression
- Tension
- Shear
- Torsion
Poisson’s Ratio
-Lateral strain/normal strain
Shear Stresses
tau=F/A
gamma=tau/G
Biaxial Loading
el=σl/E-vσt/E
et=σt/E-vσl/E
What dictates σ-e in composites?
E is determined by both fibre and matrix
e to failure determined by fibre
What is toughness?
The ability to consume energy before failure. Area under a σ-e curve
What is impact toughness?
Energy to fracture a notched specimen
What is Fracture toughness?
Measure of energy to fail a specimen containing a crack
Which properties change in a metal with temperature?
- Ultimate Tensile Strength
- Modulus of Elasticity
- Yield Strength
- Elongation
Which properties change in a polymer with temperature?
- Modulus of elasticity
- Elongation
- “Glass transition temperature”
Name the effects of high temperature on metals?
- Creep
- Low yield strength (easier to deform practically)
- Thermal Stresses
Coefficent of Thermal expansion
alpha=1/Volume dV/dT
Metal properties at high temperature?
Decrease in mechanical properties
Decrease in fatigue properties
Increase in Thermal σ
Metal properties at low temps.
Increase in mechanical properties
Increase in resistance to Plastic Deformation
Decrease in reaction and diffusion rates
