334 Final
Terms
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- Describe DFM
- Designing products while keeping manufacturing in mind.
- What does DFM stand for?
- Design for manufacturing
- What is the purpose of DFM?
- Meet end use requirments with low cost design, low cost material and low cost process combos.
- List and describe two types of unsaturated Polyester resins.
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Orthophthalic: Cheap, general purpose, MW < Iso and Terra, poorer thermal stability and chem resistance.
Isophthalic: Greater strength, heat resistance, thoughness and flexibility over ortho
Terraphthalic
Bisphenol A Fumarate: Hard, rigid and thermally stable.
Chlorendic: Extremely righid, some fire retardancy, outstanding thermal stability and resistance to oxidizing enviros. - Give three reasons to use an unsaturated polyester over an epoxy.
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Low cost
Lower weathering resistance
Lower physcial properties - Give three reasons to use a vinylester over a polyester
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Better mechanical properties
Better fiber wet out
Tailor properties easier
Less shrink - Is it important to have the correct ratios of epoxy resin and hardner?
- Yes. Important to have the correct ratio to achieve optimum properties..
- Two advantages of a thermoplastic matrix over a thermoset.
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Doesn't need to be frozen
Inexpensive
No special processing equipment necessary
Less processing time
Lower equipment costs - Describe three kinds of fiberglass:
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E: Excellent electrical insulator
S: 40% improved physical strength over E.
A: High alkaline glass
C: Combo of borosilicate and sodalime, great chem resist.
D: Low dielectric composition.
R: Alkali resistant (concrete)
Hollow Fiber: Tube like, aircraft
Te: Japanese S glass (better) - What plays the biggest role in determining the properties of a fiberglass product?
- Glass type plays the largest role.
- Two starting materials of carbon fiber and characteristics of each.
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Pitch: High modulus, low strain to failure rate, high cost, can be difficult to handle.
Pan: High strength, improved strain to failure, workable and availabe in many forms. - List and describe surface treatments for carbon fiber
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Whiskerization: Tiny ceramic crystals are grown perpendicular to fiber axis.
Pyrolitic: Addition of pyrolitic carbons by vapor deposition.
Polygrafting: Introducing a p'mer to bridge any voids and gaps between matrix and fibers - What is interlaminar shear strength?
- The attraction or shear strength between sheets so the sheets do not delaminate.
- Roving:
- Collection of continuous strands or filaments parallel to each other.
- Woven Roving:
- Many rovings woven into heavy, coarse fabrics.
- Mats:
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Chopped strand: nonwoven
Continuous
Vail - Yarn:
- Fibers are twisted slightly.
- Textured yarn:
- Textured by air breaking surface filaments. Bulkier.
- List four properties of aramid:
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Poor UV resistance
Good impact resistance
Poor bonding abilities
Fire retardant
Good creep resistance
Weak in bending - What is the first thing you do when given a project? (Part of the material selection process)
- Determine the products funtions and objectives.
- How do you obtain fire retardancy in polyesters and vinylesters?
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Add clays: Bad effects on properties
Add halogens: small effect on properties - Why don't we see high performance polyethylene fibers more in composites?
- They're inert and won't bond very well.
- What is the primary function of the facing material in sandwich construction?
- To provide bending and in plane shear support. Caries the edgewise, bending and shear loads.
- Design checklist for a composite structure:
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1. Clear objective
2. Quantitative measures for using composites.
3. Mfg. approach
4. Known material and properties of that material
5. Material procurement
6. Joint concepts
7. Verify design
8. Inspections. - Should you use design data from tables?
- Always test it yourself due to variation.
- Name 3 core types and reason to use each:
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Wood: Relatively inexpensive, easy to work with
Honeycomb: Different shapes for different contours available
Foam: Spray in place! Radar transparancy - When performing a hand lay up, what are four things the tool needs or does?
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Consider resin flow
Correct CTEs
Draft at least 1 degree
Surface finish
Tolerances
Room for tacky tape. - Three reasons to use hand lay up and three not to.
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Good:
- Low tooling cost
- Low skilled labor needed
- Large parts can be made
- More complex parts
Bad:
- Labor intensive
- One tooled surface
- Long cycle time
- High waste
- Part to part variation - Describe the difference between RTM and VARTM.
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RTM: Two tooled surface, no vacuum assist.
VARTM: Vacuum pulls resin, one tooled surface - If the part has not been symmetrically hand laid up, what happens?
- The part will warp and curl because of internal stresses.