Advanced Thermoset Resins for Composites 130

abrasion

Damage from repeated rubbing or scraping that is concentrated in the same place. Harder materials resist abrasions.

advanced composite

A composite made from specially formulated resins and high performance fibers. Advanced composites are used for applications that require a customized mixture of resins and reinforcements to produce specific properties in the composite.

amide

An organic compound used as a hardening agent in epoxy resins. Amides form weaker bases than amines.

amine

An organic compound derived from ammonia. Amines are used as hardening agents in epoxy resins.

aromatic compound

A highly stable type of chemical used in phenolic resins. Aromatic compounds often have a strong odor.

autoclave

A pressure vessel that promotes faster curing through a combination of vacuum and heat.

base

The first of two components that make up an epoxy. The base is essentially a resin.

brittleness

The measure of a material's tendency to fracture from being drawn, stretched, or formed. As the rigidity of a material increases, brittleness increases as well.

ceramic matrix

A high-performance composite matrix made from oxide, carbide, nitride, or boride. Ceramic matrices can withstand extremely high temperatures and are used for specialized applications such as aerospace.

cracking

Visible fractures or points of separation on the surface of the composite. Cracking is one of the most common defects in composite parts.

creep

The slow deformation of a material over time due to the presence of a constant load. Composites with a polymer matrix tend to be more vulnerable to creep than metal matrix or ceramic matrix composites.

cross-linking

The development of primary bonds between polymer molecules. Thermosets are heavily cross-linked, while thermoplastics are not cross-linked, or are cross-linked to a weaker degree.

cyanate ester

A relatively new thermoset polymer that is sometimes used as a substitute for epoxy. Cyanate has better strength, thermal stability, and water resistance than epoxy.

cycle time

The amount of time required to prepare, process, and cure composite materials in a mold. Polyurethane is valued for its relatively short cycle times.

dicyclopentadiene

DCPD. A chemical compound used enhance the properties of resins. Dicyclopentadiene is added to epoxy resins to increase their toughness and thermal stability.

dielectric loss

The loss of energy in an electrically insulating material. A material with low dielectric loss dissipates a relatively low amount of heat when subjected to electrical current.

epoxy

The most common thermoset polymer used for advanced composite resins. Epoxies are very tough and heat-resistant compared to other polymers.

filament winding

A process during which strands of fiber are soaked in resin and wound around a core in the desired pattern.

flexibility

The measure of a material's ability to flex or bend. Flexible materials are better able to absorb impact without breaking.

glass transition temperature

Tg. The temperature at which a rigid solid becomes pliable and can be formed, shaped, or molded. In general, a higher Tg allows for greater thermal stability and helps to prevent defects during the curing of a part.

hardening agent

A chemical that facilitates curing in resins. In epoxies, the hardening agent is usually an amine or an amide.

hardness

A material’s ability to resist deformation from impact. Composite materials are often rated according to a hardness scale in which a higher score indicates a harder material.

initiator

An ingredient used to facilitate chemical reactions.

laminate

Two or more layers of fibrous material that have been bonded together for strength. Composite parts are often made up of laminates.

load

The overall force applied to a material or structure. In a composite, the matrix transfers the load to the reinforcement fibers.

major epoxy

The main ingredient of the base of an epoxy.

matrix

The material that binds together the reinforcing fibers of a composite. Advanced composites use specially formulated resins as the matrix.

metal matrix

A high-performance composite matrix made from a metal or a metallic alloy. Metal matrices are extremely strong and are used for specialized applications such as aerospace.

minor epoxies

Additional ingredients added to the base of an epoxy to change the viscosity of the resin.

nanofiller

A tiny inorganic particle used in advanced composites. Nanofillers improve the appearance and mechanical properties of composite parts.

nanometer

An extremely small unit of measurement. One nanometer equals the size of a small molecule.

phenol

An aromatic compound used to create phenolic resins. Phenol has a strong odor and can be toxic in high concentrations.

phenolics

A group of thermoset polymers derived from phenol. Phenolic resins are highly resistant to heat and fire.

polyimides

A group of thermoset polymers with the highest heat resistance of all polymers. Polyimides are often used to make composite parts in the aerospace industry.

polymer

A long chain of very large molecules made up of many atoms. Thermoset polymers are preferred over thermoplastic polymers for advanced composite resins.

polyurethane

A thermoset polymer that was originally developed as a replacement for rubber. Polyurethane resins have low viscosity and rapid cure times, but they are not as heat-resistant as other thermosets.

pultrusion

A molding process in which heated resin cures as it is pulled through a die. Pultrusion is a variation of the extrusion process, during which resin is pushed through a die.

reinforced reaction injection molding

RRIM. A type of injection molding in which the resin and reinforcement are mixed together and injected into the mold at the same time.

reinforcement

The part of the composite that provides strength, stiffness, and the ability to carry a load. The reinforcement material used in advanced composites is often a high-performance fiber.

resin

A substance made from either synthetic or natural polymers and used for composite matrices. In essence, a resin is a polymer that has not been processed into its final form.

resin transfer molding

RTM. A type of liquid molding in which resin held in a separate transfer chamber is added to the mold through pressurized injection. DCPD additives are ideal for epoxy resins used in resin transfer molding.

Rockwell scale

A hardness scale developed by Hugh and Stanley Rockwell in the early 1900s. Several other hardness scales exist, but the Rockwell scale is known for the speed and reliability of its testing methods.

sandwich panel

A composite structure in which two stiff outer skins are bonded to a relatively thick but lightweight core.

shrinkage

The reduction in the size of a part after it has changed from a liquid to a solid. Phenolic resins have a high amount of shrinkage during curing.

silicone

A polymer that can exist in various forms. Silicone resins have good thermal stability.

spray-up molding

A manual molding process during which an operator uses a spray machine to simultaneously apply resin and chopped fiberglass strands to an open mold.

strength

The ability of a material to carry a load. In a composite, strength refers to the ability to carry a load in the preferred direction.

structural reaction injection molding

SRIM. A type of injection molding in which thermoset resin is injected into a preform and subjected to pressure and heat until it cures.

thermoplastic

A polymer in which the molecules are not cross-linked, or they are cross-linked to a weaker degree. Thermoplastics can be melted and hardened repeatedly without changing their chemical structure.

thermoset

A polymer that cannot be re-melted or reformed once it has cured. Thermosets have higher rigidity and better thermal stability than thermoplastics.

toughness

The measure of the composite's ability to absorb mechanical forces before it breaks. Increasing the amount of cross-linking in the resin creates a tougher composite.

traditional composite

A composite that uses a relatively consistent combination of resin and fiberglass reinforcement. Traditional composites are low-cost and are processed by traditional methods.

viscous

Having a high resistance to flow. Viscous fluids tend to be sticky or syrupy.

volatile condensation

Gas that has changed to liquid form. Volatile condensation must be removed from composite parts before it becomes trapped in the resin in the form of voids and weakens the composite matrix.