Some of the more common thermosets include epoxy, polyurethanes, phenolic and amino resins, bismaleimides (BMI, polyimides), polyamides.
These compounds are very important because they control the reaction rate and determine the performance characteristics of the finished part.
The bismaleimides and polyamides are relative newcomers to the advanced composite industry and have not been studied to the extent of the other resins.
They are typically supplied as nonreactive solids (no chemical reaction occurs during processing) and require only heat and pressure to form the finished part.
Fiberglass has a relatively low stiffness at the same time exhibits a competitive tensile strength compared to other fibers.
Thus, the reinforcing fibers maybe arranged and oriented in different forms and directions to provide different physical properties and advantages based on the application.
[9] Carbon nanotubes in particular have been intensely studied due to their exceptional intrinsic mechanical properties and low densities.
Stress-strain studies of single-walled carbon nanotubes in a polyethylene matrix using molecular dynamics showed that long carbon nanotubes lead to an increase in tensile stiffness and strength due to the large-distance stress transfer and crack propagation prevention.
[10] However once modified, short carbon nanotubes are able to further improve the stiffness of the composite, however there is still very little crack propagation countering.
[11] In general, long and high aspect ratio carbon nanotubes lead to greater enhancement of mechanical properties, but are more difficult to process.
Non-covalent CNT modification involves the adsorption or wrapping of polymers to the carbon nanotube surface, usually via van der Waals or π-stacking interactions.
[12] Covalent functionalization can be used to directly attach the polymer to the carbon nanotube, or to add an initiator molecule which can then be used for further reactions.
Additionally, 3D graphene polymer composites show some promise for the isotropic enhancement of mechanical properties.