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30 Cards in this Set
- Front
- Back
Describe DFM
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Designing products while keeping manufacturing in mind.
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What does DFM stand for?
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Design for manufacturing
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What is the purpose of DFM?
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Meet end use requirments with low cost design, low cost material and low cost process combos.
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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. |
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Give three reasons to use an unsaturated polyester over an epoxy.
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Low cost
Lower weathering resistance Lower physcial properties |
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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 |
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Is it important to have the correct ratios of epoxy resin and hardner?
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Yes. Important to have the correct ratio to achieve optimum properties..
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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 |
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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) |
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What plays the biggest role in determining the properties of a fiberglass product?
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Glass type plays the largest role.
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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. |
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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 |
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What is interlaminar shear strength?
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The attraction or shear strength between sheets so the sheets do not delaminate.
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Roving:
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Collection of continuous strands or filaments parallel to each other.
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Woven Roving:
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Many rovings woven into heavy, coarse fabrics.
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Mats:
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Chopped strand: nonwoven
Continuous Vail |
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Yarn:
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Fibers are twisted slightly.
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Textured yarn:
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Textured by air breaking surface filaments. Bulkier.
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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 |
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What is the first thing you do when given a project? (Part of the material selection process)
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Determine the products funtions and objectives.
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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 |
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Why don't we see high performance polyethylene fibers more in composites?
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They're inert and won't bond very well.
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What is the primary function of the facing material in sandwich construction?
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To provide bending and in plane shear support. Caries the edgewise, bending and shear loads.
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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. |
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Should you use design data from tables?
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Always test it yourself due to variation.
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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 |
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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. |
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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 |
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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 |
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If the part has not been symmetrically hand laid up, what happens?
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The part will warp and curl because of internal stresses.
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