Untitled Notes

Open Mold Manufacturing: Two subsets; wet layup and VARTM. Wet layup has multiple subsets, including spray up, Vacuum bagging, and no bag
VARTM: has an unlimited setup time, requires low-viscosity resin, operator dependent, good for prototyping, one tooled surface, vacuum only, not repeatable process
Wet Layup with vacuum bagging: identical in process to the wet layup with no bag except there’s a bag, the purpose of the bag is to draw out voids and resin to increase the volume fraction of fibers, good for prototyping, large and complex shapes OK, low production, quality is operator-dependent, fewer voids
Wet Layup, No Bag: No bagging material cost, very low startup cost, just need tool, release, and resin, good for prototyping, low production, quality is operator-dependent, high probability of voids
Spray Up: Medium production, low-skilled labor, can be automated, inexpensive tooling, good for prototyping, dirty, potential health hazards, non-automated quality is operator-dependent, possibility of voids is high, produces non-structural components
Light RTM, LRTM: No pressure it’s a vacuum only process, 2 tooled surfaces, matched die, room temp cure, tooling just has to withstand vacuum pressure, no expensive equipment, low-viscosity resin onlym low to medium production
Resin Transfer Molding, RTM: Two tooled surfaces, matched die, starts with dry fibers, pre form is held with a binder in the shape of the part, no skilled labor, more expensive mold, repeatable part/process, part size is determined by equipment
Metal matrix: Forged with short strands thrown in, typically not used with long fibers, uses ceramic fibers only
Ceramic Matrices: defined as neither organic not metallic, chemically and thermally resistant, brittle, corrosion resistant, dimensionally stable, not used in structural applications
PEI, Polyetherimide: aka Ultem, high temp resistance, high stregnth, flame resistant, ductile, Strength comes from chlorinated solvents
PPS, Polyphenylene Sulfide: high temp and chemical resistance, dimensionally stable, flame retardant, brittle, flows well
PEEK, Polyether ether ketone: high property long fibers, advanced composites
Polyurethane: Phenolic matrix, cross links with condensation reaction but no condensate, not traditionally associated with composites, tough, many grades, better adhesion than polyester, abrasion resistant, cost is 10 to 20% higher than p’ester, TS = 2 to 7ksi, %E is 5 to 55%, great at cryogenic applications
Phenolic: Aka bakelite, first thermoset ever developed, made by adding phenol and formaldehyde, Cost is 10 to 15% higher than p’ester, brittle, highly electrically resistant, doesn’t burn, or produce smoke, low heat transfer, resistant to chlorine solvents, good adhesion properties, High shrinkage, TS is 6 to 8 ksi
Post Cure: Additional curing step at elevated temperature to ‘finish’ the cure, depends on the resin system and mix
Stages of Cure in a thermoset:

mix in pot, t=0
gel point, resin is too viscous to flow properly for fiber wet out, t=1-4hrs
almost tack-free, is the last stage where the surface is still active, gloved finger can impact the surface, t=5-11hrs
hardening, glove leaves no finger print but can indent with fingernail, t=8-18hrs, x-link=30%
Earliest sanding time, firm enough to withstand abrasion, t=16-36hrs
earliest loading time, first time the part can be loaded as intended without damaging it, t=up to one week
full cure, <80% x-linking complete which means it’s fully cured (assuming it was mixed correctly)

Inhibitor: Slows down epoxy cure
The only way to speed up the cure of an epoxy, is with additives or heat
Adding carbon black to epoxy increases UV resistance, but impacts its material properties
Adding a halogen to an epoxy inhibits burning, but impacts its material properties
Increasing the toughness of an epoxy with additives impacts its mechanical properties
Anhydride Curing Agent: solid at RT, elevated temp cure of 200C, long pot life of two months, thermally and electrically resistant, low toxicity
Epoxy: other than polyester it is the 2nd most common, modified condensation reaction with no condensate, parts A and B need to be in equal parts to get as much saturation and x-linking as possible
Epoxy in General: has higher mechanical properties than polyester and vinylester, high free surface energy makes it a good adhesive and great for wet out, doesn’t off gas, is chemically resistant, creep resistant, electrically and thermally insulative, fatigue resistant, sensitizer, brittle, poor UV resistance
Vinylester: aka epoxy vinylester but it is NOT an epoxy it has more in common with polyester and is referred to as an epoxy because of its epoxy backone, addition reaction to x-link, tougher and more corrosion resistant than p’ester, easily wets out fiber, expensive gel coats use this as a base, competes with p’ester, has a hard gel point, absorbs less water than p’ester
Pot life: Working time you have before the viscosity is too high for use
Gel Coat: Protective or decorative surfaces, non structural, polyester is most common resin base, highly pigmented-opaque, more viscous than neat resin, liquid resin, sprayed or painted on, used in boats, car parts, hot tubs, showers
Acrylic: aka bondo, unsaturated p’ester resin as base then add fillers and short fibers, you add the initiator, paste and resin leads to hardened product
BMC, Bulk Molding Compound: p’ester resin and initiator with retardant, fibers and fillers, consistency of cookie dough
SMC, Short Molding Compound: Same material as BMC but is pressed into a sheet
Terephthalic Resin (Tere): slight boost in TS compared to HDT and ISO, used to make Petroleum storage tanks, not very common
Isophthalic Polyester Resin (ISO): Increased stiffness and strength compared to ortho, increased heat deflection temperature of 235F, laminating resin
Orthophthalic Resin (Ortho): least expensive, lowest properties, general purpose, most common, HDT of 150F
Thermoset Polyester: aka unsaturated polyester resin, lowest cost, lowest performance, low temp, low physical and mechanical properties, most common resin system, x-links with addition reaction, has hard gel point
Matrix Dominated Properties: Shape, abrasion resistance, elemental resistance (UV, chemical), surface finish, temp resistance hardness, fire resistance
Higher molecular weight means higher stiffness, strength, hardness, abrasion resistance, and viscosity
Higher molecular weight means higher mechanical properties
Higher x-link density means higher molecular weight
Aromatic: has a benzene ring
Aliphatic: doesn’t have a benzene ring
High viscosity makes for more difficult wet out
Fiber glass is the most common fiber
Fiber glass: moderate tensile strength, heat and fire resistance, chemically resistant, environmental resistance, inexpensive, very available, many forms available, thermally and electrically insulative, moderate modulus of elasticity, milk toast, higher density than other fibers
S-Glass: for structural purposes, high mechanical properties, high price, TS is 665 ksi, E is 12msi
E-Glass: bottom of the barrel, most common fiber glass, lowest cost, commodity, lowest properties TS and E, TS is 500 ksi, E is 10 msi
Carbon Fiber: Nikki calls this “the least green material”, takes a LOT of energy to make, has incredible stiffness, is known for being the stiffest known material, average TS, temp resistant, negative CTE, compressive strength less than tensile, fatigue resistant, electrically and thermally conductive, creep resistant, expensive
Wet Out: the ability of a resin to surround a fiber
Oxidative Surface Treatment: used to improve wet out, fibers are drawn through nitric acid bath for etching
Non-Oxidation Surface Treatment: used to improve wet out, methods include whiskerization, pyrolitic coating, and polymer grafting
UHMWPE: Tough, it absorbs energy when impacted, challenge to wet out, low temp, melting point of 290F, low density, highest STS and SM than any known material due to extremely low density, resistant to microbes, high creep
FLAX: low temp only, absorbs H2O, lower density than fiber glass, lower flexural properties, creeps, hard to wet out as it absorbs everything, competes with fiber glass
Fiber forms: filament, tow, roving, mat
Filament: a single fiber
Tow: collection of fillaments
Roving: many, many, many filaments - a big tow
Mat: no fiber orientation
Chopped strand: fiber lengths of a couple inches, uses a binder to hold the strands together
Continuous fiber: continuous fiber held with string
Veil: thin mat, good in deep contours, no bulk, can be chopped strand or continuous fiber
Warp: Roll notation, describes the direction of the roll that is parallel to the direction you’d pull a sheet of paper towel
Fill: Roll notation, describes the direction of the roll that is parallel to the direction of a paper towel roll
Drape: how well the material fits into all the contours of the mold
Plain Weave: 1 under 1 over, the most stable weave, least drape-able, easiest to handle
Ply: each layer in the laminate
Laminate: layers of ply
Filament becomes roving when it is made into a fabric, it becomes woven roving
Male Tool: can make a female form that is called a splash which is more durable than a foam female, layup on the outside of the part, draft is needed on the outside of the part, one tooled surface
Female Tool: cavity mold, need draft to be able to pull part
PMC stands for Polymer Matrix Composite
MMC stands for Metal Matrix Composite
CMC stands for Ceramic Matrix Composite
FRP stands for Fiber Reinforced Plastic
Two Groups of composites: Engineering and Advanced. Engineering composites use short fibers, have low properties, low cost, not highly engineered. Advanced composites use high performance fibers and resins, high thermal and mechanical properties, highly engineered, used in aerospace and sporting goods
Why you would use polymer matrix composites over metal: specific strength and stiffness, light weight, typically elec and thermal insulative, easy to bond, fatigue resistant, corrosion resistant, low CTE, complex shapes are easy, tailor properties