Composites Vocabulary

Prepreg

A type of composite material in which the reinforcing fibers are encapsulated in an uncured resin. These materials must be kept refrigerated to prevent them from curing before they are used.

Warp

Become or cause to become bent or twisted out of shape, typically as a result of the effects of heat or dampness.

Void

Completely empty.

Selvage Edge

The edge of cloth, tape, or webbing woven to prevent raveling.

Matrix

The material used in composite construction to bond the fibers together and to transmit the forces into the fibers. Resins are the most widely used matrix materials.

Bias

A cut, fold, or seam made diagonally to the warp or fill threads.

Crazing

A form of stress-caused damage that occurs in a transparent thermoplastic material. It appears as a series of tiny, hair-like cracks just below the surface of the plastic.

Heat Bonder

A portable device that automatically controls heating based on temperature feedback from the repair area. They also have a vacuum pump that supplies and monitors the vacuum in the vacuum bag.

Autoclave

A pressure vessel inside of which air can be heated to a high temperature and pressure raised to a high value. They are used in the composite manufacturing industry to apply heat and pressure for curing resins.

Thermoplastic Resin

A type of plastic material that becomes soft when heated and hardens when cooled.

Thermosetting Resin

A type of plastic material that, when once hardened by heat, cannot be hardened by being heated again.

Warp Clock

An alignment indicator included in a structural repair manual to show the orientation of the piles of a composite material. The ply direction is shown in relation to a reference direction.

Isotropic

An object or substance that has the same physical property when measured in different directions.

Bleeder Ply

Creates a path for the air and volatiles to escape from the repair. Excess resin is collected in the bleeder.

Core

Materials that are used to complete the function of engineered structures by making up for a type design or performance need, whether it's weight reduction, providing energy absorption, impact resistance, or adding stiffness.

Peel Ply

Often used to create a clean surface for bonding purposes. A thin layer of fiberglass is cured with the repair part. Just before the part is bonded to another structure, the peel ply is removed. It is easy to remove and leaves a clean surface for bonding.

Caul Plate

Smooth metal plates, free of surface defects, the same size and shape as a composite lay-up, used immediately in contact with the lay up during the curing process. They transmit normal pressure and temperature, and provide a smooth surface on the finished laminate.

Hybrid

Something made by combining two elements together. A mixture.

Composite

Something made up of different materials combined in such a way that the characteristics of the resulting material are different from any f the components.

"A Stage Curing"

The components of the resin (base material and hardener) have been mixed but the chemical reaction has not started. The resin is in this stage during a wet layup procedure.

"B Stage" curing

The components of the resin have been mixed and the chemical reaction has started. The material has thickened and is tacky. The resins of prepreg materials are in the B stage. To prevent further curing the resin is placed in a freezer at 0 degrees F. In the frozen state, the resin of the prepreg material stays in the B stage. The curing starts when the material is removed from the freezer and warmed again.

"C Stage" curing

The resin is fully cured. Some resins cure at room temperature and others need an elevated temperature cure cycle to fully cure.

Fill

Threads that run across the width of the fabric, interweaving with warp threads.

Debond

To remove a bonding agent such as glue, or to free from such a bonding.

Release Agent

Used so that the part comes off the tool or caul plate easily after curing.