The Fibre Phase Flashcards
What is the diameter of whiskers?
10-100nm
What is the diameter of fibres?
5-15μm
What is the diameter of wires?
0.1-1mm
What are some aspects of whiskers?
-highly crystaline
- low flaws
- high strength
- high AR
- difficult to combine into a matrix
- expensive
- health concerns
What is the cost, modulus and strength of glass fibres
Low
Medium
Medium-hig
What is the cost, modulus and strength of carbon fibres
high
high-veryhigh
high-veryhigh
What is the cost, modulus and strength of Polymeric fibres?
medium-high
for all
Are glass fibreanisotropic or isotropic?
Isotropic
same proterties parallel to fibre direction as perpendicular
What is the chemical structure of glass fibres?
series of interconnected tetrahedral SiO2 groups repeated in 3D
- silicon at centre
- Oxygen at vertices
- strong covalent bonds
What are the 3 types of glass fibre used in composites and there properties?
E-glass(electrical) - good strength, stiffness, electrical and weathering properties CHEAP
C-glass(corrosion) - better corrosion resistance but lower strength
S-glass(strength) - Expensive but higher strength, tensile modulus and temp resistance
Applications of glass fibres
Marine
Automotive
Military
Construction
Storage
Baths
How are glass fibres manufactured?
- weigh and dry oxide powders
- refractory furnace, melt and homogenise @1370*C
- refiner to complete homogenisation and remove bubbles @1340*C
- Forehearth @1250*C for extrusion through platinum bushings
- Draw fibres at 60m/s
- Quench fibres using air or water
- Sizing
- Process
How is the diameter of glass fibres controlled?
- Viscosity of the melt
- Size of bushing holes
- Drawing speed
What are different processing options of glass fibres?
Continuous strand - >100mm (long)
Chopped strand 3-100mm (short)
Hammer milled 30μm-3mm (particulate)
What does sizing do to glass fibres?
- protect fibres
- binds fibres together
- lubricate fibres to reduce abrasion
- impart anti static properties
- Chemical link between fibres and matrix
What does a typical sizing consist of?
- Protective polymeric film (PVA)
- Small molecule acts as lubricant
- Coupling agent to promote adhesion (organosilane)
What happens when glass fibres readily absorb water?
Na and Ca are leached out leaving it porous and weak