Lecture 3: Fibers Flashcards
What are the four factors that govern fiber contribution?
- Mechanical properties
- Interaction at interfaces
- Volume fraction
- Orientation
What is the difference between organic and inorganic fibers?
Organic - low density, flexibility, elasticity
Inorganic - high thermal stability, stiffer
If a fiber is inorganic, it is harder to incorporate into matrix. True or false?
True. (i.e. glass)
What are the advantages of FRPs, or fiber-reinforced polymers?
In construction industry:
1. shock absorption
2. safer because it can absorb energy and provide a dampening effect
3. easy installation (lightweight
4. decrease thermal expansion (metals won’t expand)
5. Better fatigue strength
When is fiber length said to be continuous?
When it’s at least 15 times greater than the critical length value.
What are the advantages of glass fibers?
- inexpensive
- easier to manufacture
- relatively high strength and stiffness wrt to polymer matrix
What are the different glass types?
E glass (good tensile and compressive strength, good for electrical properties, poor impact resistance )
C glass (chemical attack)
R/S/T glass (high tensile strength - aerospace)
How are glass fibers produced?
blending quarry products at high temp, and passed through microfine bushings, cooled, and drawn, coated
Why to fibers have to be cooled rapidly through Tg during drawing?
So crystallization can be prevented
What are the advantages of glass fibers?
- low density
- high temp resistance
- transparency -> same color as matrix
- isotropy
What are the main disadvantages of glass fibers?
- prone to surface damage
- dissolution of some of the oxides by moisture
Why do aramid fibers have very high impact strength and energy absorption?
It’s due to the benzene rings and intermolecular hydrogen bonding. High packing efficiency.
Why are aramid fibers more flexible than glass fibers?
They have spacers, which gives the molecules more space to vibrate and twist.
Why do aramid fibers have yellow discoloration and moisture absorption?
- Benzene -> quinoid upon rearrangement
- Absorb moisture due to hydrogen bonding
What are the advantages of armaid?
No melting point
Low flammability
Less abrasions
