Lecture 7 - Composites Flashcards
What are the Shaping Processes for Polymer Matrix Composites?
- Open mold process
-Closed mold process
-Filament winding
-Pultrusion process
-Other PMC shaping process
What is a PMC?
A composite material consisting of a polymer imbedded with a reinforcing such as fibers or powders
-Fiber Reinforced Polymers being the most used
Advantages of PMC/FRP composites and common applications?
-High strength to weight ratio
-Modulus to weight ratio
-Low specific gravity
Used in automotive, aircrafts, and boats
What are typical Polymer Matrix materials?
Thermosetting Polymers (Polyesters, epoxies Phenolics)
Thermoplastics are used as fillers or reinforcing agents
What types of reinforcing agents are there?
-Ceramics, metals, other polymers, or elements such as carbon or boron
-All come in shapes varying from Fibers, particles, and flakes (fibers being the most common)
What types of Fibers are there?
Materials:
-Glass, carbon, and kevlar
Geometry:
-Continuous fiber or chopped fiber
-Mat or woven
Disadvantages for PMC/FRP composites?
slow and labor intensive shaping process
difficult to repair
Explain The Open Mold process?
The starting materials (resins, fibers, mats…) are applied to molds (either negative or positive) in layers build to desired thickness
Then given time to cure and final removal from mold
this process can be hand lay up or spray up
What are the differences between hand lay up and spray up?
hand layup involves laying each layer of reinforcement by hand, followed by rolling to release air gaps and apply resin. Process is repeated until desired thickness
Spray layup uses a spray gun to spray resin into mold along with chopped fibers, less labor intensive
Explain the Closed mold process and some advantages
Follows the same process as open mold, but the PMC is sandwiched between two molds during the curing cycles
it provides a better surface quality on both sides
higher production rates
closer control over tolerances
more complex designs are achievable
Explain the filament winding process.
Continuous fibers are wrapped around a rotating mandrel that has the internal shape of desire product until desired thickness has been achieved. Epoxy is given time to cure then mandrel mold is removed.
Explain the Pultrusion process
An extrusion process that involved pulling the material through a die resulting in continuous straight sections of constant cross sections. used for Rods, bars, Tubing, Flat sheets and Structural shapes
Name the 2 kinds of rubbers
Natural rubber, coming from agriculture
Synthetic Rubber, based on petroleum
Types of Rubber processing are?
Compounding
Mixing
Shaping
Vulcanizing
What is the rubber compounding process?
Adding chemicals to rubber to enhance the rubbers mechanical properties to satisfy the given application
