230523 - Polymer technology Flashcards
Hand laminating advantages
simple procedure
low investment costs
prototype construction
disadvantages of hand lamination
low reproducibility
low fiber volume contents
reduce bubbles
vacuum foil
laminate is compacted and excess matrix is removed
better mechanical properties
Prepreg
Ribbons and tapes
* pre impregnated fiber matrix: thermoset or thermoplastic resin matrix, typically epoxy. Prepregs have the resin matrix pre-impregnated and partially or fully cured, requiring a curing process to achieve final properties. UD tapes, on the other hand, have dry or lightly coated fibers and require additional consolidation steps, such as heat and pressure
* store at -20 deg, consolidation temperatures up to 230deg:
1) cold hardening (room temperature, low quality, low mechanical properties)
2) warm hardening (high temp, high pressure, better quality)
- Consistent quality and performance: precise and consistent ratio of resin to fiber. The resin is evenly distributed throughout the fibers, ensuring optimal impregnation and avoiding excess resin
- Ready-to-use, resin in prepreg is partially cured
Autoclave process
- Hydrostatic pressure holds the pressure all around the 3D shape. Autoclave, which is a specialized pressure vessel that provides controlled temperature, pressure, and vacuum. (kind of a pressure cooker), also used to sterilize materials.
- high-performance applications such as aerospace
ADVANTAGES: - high fiber volume content (70%)
- high reproducibility
- few defects
DISADVANTAGES: - high investment costs
- high operating costs
- limited component size
Processes for thermoset materials
hand lamination
with pressure
with vacuum
(low demand, high cycle times)
* injection and infusion (short cycle times)
Resin injection and infusion procedure
1) Injection:
liquid resin is typically mixed or prepared separately
injected into the mold cavity through the inlet port using pumps, syringes, or other injection equipment
2) Infusion:
* a vacuum bag creates a vacuum pressure inside the bag, which helps facilitate the resin flow.
* Control: vacuum level, resin viscosity, and the placement of distribution channels.
ADVANTAGES:
* shorter cycles
* sandwich through the use of foam cores
* high component quality
DISADVANTAGES:
* complex preforming (correct positioning of the foil, no folded parts)
* careful positioning of the
dynamic mixing of components
a piston pulls out and the same channel is used to mix the components
static
separate channels for each component
vacuum infusion
vacuum sucks the matrix to the preformed textile, previously covered with a vacuum foil
simple process
large components possible
partial automation
vacuum scrimp method
feed line perpendicular to the surface of the part
* Seemann Composites Resin Infusion Moulding Process
Sustainability issues with composite polymers
- Energy-intensive processes, such as resin curing and fiber manufacturing. These processes typically require high temperatures, long curing times, and specialized equipment, resulting in significant energy consumption
- composite polymers are not easily recyclable, complex mix of materials and their composite structure.
RTM
resin transfer moulding
injection
* gelcoatings possible
* textile, close the press to form the shape (simple parts), injection of resin and fiber, temperature control and demould
release agent can be included already in the resin
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high fiber content (difficult flow) and viscosity of the resin can influence the behavior, high injection speeds can generate air bubbles
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latent chemical reaction (inhibitor, and this produces a reaction after a threshold, temperature, UV light)
Structural reaction injection molding
- fast filling due to hydraulic injection
- mixing happens in the tool (rapid injection is needed to avoid hardening of material)
Hot pressing process
Feed tool, press it, heating (galing point, first networks inside the polymer), exothermic curing reaction, demoulding
one of the first polymer production processes
b state polymer, precured, a powder
