Glossary of Composites Terms

Adhesive 
A thermoset resin (e.g., epoxy, phenolic or BMI) in the form of a thin film or paste, cured under heat and pressure to bond a wide range of composite, metallic and honeycomb surfaces.

Aramid 
A high strength, high stiffness fiber derived from polymid. Kevlar(tm) and Nomex(tm) are examples of aramids.

Carbon Fiber 
Fiber produced by carbonizing precursor fibers based on PAN (polyacrylonitrile), rayon or pitch. The term is often used interchangeably with graphite. However, carbon fibers and graphite fibers are made and heat treated at different temperatures and have different carbon contents.

Composite Material 
Product made by combining two or more dissimilar materials such as fibers and resins to create a product with exceptional structural properties not present in the original materials.

Cowls or Cowling 
The outside protective shell of a jet engine, traditionally made out of metal. Cowls mainly provide the engine with protection from the elements and with structural support.

Engineered Core 
The forming, shaping, machining or bonding of sheets or blocks of honeycomb into profiled and complex shapes for use as semi-finished components in the fabrication of composite parts and structures.

Engineered Products 
Completed composite components that typically are manufactured from prepregs, honeycomb, adhesives and assembled hardware. These parts are ready for direct attachment to a structure (e.g., aircraft) or to sub-assemblies. Emerging manufacturing processes allow the fabrication of engineered products directly from reinforcing fibers/fabrics and matrix resins.

Fairing 
A secondary structure of an airplane providing enhanced aerodynamics. Typically, fairings are found where the wing meets the body or at various locations on the leading or trailing edge of the wing.

Fiberglass 
Filaments made by drawing molten glass. Woven by Hexcel into fabrics and commonly used as a composite reinforcement.

Filament Winding 
A process to manufacture composite materials components such as rocket casings and cylinders. Fiber filaments are impregnated in a resin matrix and then wound in a predetermined pattern over a form of the desired component.

Honeycomb 
A unique, lightweight, cellular structure made from either metallic sheet materials or non-metallic materials (e.g., resin-impregnated paper or woven fabric) and formed into hexagonal nested cells, similar in appearance to a cross-section of beehive.

Inlet Ducts
 Intake passages or tubes that confine and conduct air. They are usually located at the upstream end of an airplane engine on the engine cowling and aid in propulsion and engine cooling.

Interiors 
Finished internal aircraft components, such as overhead stowage compartments, lavatories, sidewalls, floor panels and ceilings.

Kevlar^TM
An aramid fiber from DuPont. Woven Kevlar™ fabrics are used in both ballistic and composite materials applications.

Modulus of Elasticity 
The physical measurement of stiffness in a material. A high modulus indicates a stiff material.

Nacelle 
The protective shell of a jet engine housed within the cowling, usually made from honeycomb. Provides noise absorption, insulation, structural support and can aid heat dissipation.

Nomex^TM
DuPont's registered trade name for its high temperature resistant aramid papers, pressboard, staple fibers and filament yarns. Nomex™ aramid paper is used in the manufacture of honeycomb.

PAN (Polyacrylonitrile) 
A polymer which when spun into fiber is used as a precursor material in the manufacture of certain carbon fibers.

Precursor 
The PAN, rayon or pitch fibers from which carbon or graphite fibers are derived.

Prepreg (pre-impregnated) 
A composite material made from combining high performance reinforcement fibers or fabrics with a thermoset or thermoplastic resin matrix. When cured under high temperature and pressure, exceptional structural properties are achieved.

Primary Structure 
A critical load-bearing structure on an aircraft. If this structure is severely damaged, the aircraft cannot fly.

Radome
The housing which protects the aircraft radar system from the elements while allowing transmission of radar signals. Often the radome is in the nose of an aircraft but can be found at other locations on the aircraft, as well.

Reinforcement
A strong material which when combined with a resin matrix forms a composite material. Reinforcements are usually continuous fibers, which may be woven. Fiberglass, aramid and carbon fibers are typical reinforcements.

Reinforcement Fabrics
Woven fiberglass, carbon or aramid fabrics used in production of prepregs and honeycomb.

Resin Matrix
In reinforced fiber composites, a formulated polymeric substrate.

Sandwich Panels 
A stiff and lightweight panel consisting of thin sheets such as aluminum or cured prepreg laminate bonded to a low density, rigid core material (e.g., foam or honeycomb).

Structures 
Finished components for aircraft and industrial applications. For aircraft, these may be for primary or secondary external structures. Truck applications include chassis fairings and floors.