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Composites Terminology Database

This glossary is not an exhaustive list, however it does contain the majority of terms used in the composites industry and as part of the management of our website, it is updated on a continual basis.

The terms are accessed by clicking on the appropriate letter below, all the terms beginning with the letter Y can be found below.

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Terms Y

Click on a term and it will take you to the coresponding explanation.

In composite laminates, the axis in the plane of the laminate that is perpendicular to the x-axis.

yarn bundle
See bundle

yarn, plied
See plied yarn
"plied yarn"

An assemblage of twisted filaments, fibres, or strands, either natural or manufactured, to form a continuous length that is suitable for use in weaving or interweaving into textile materials.

Ultimate strength in compression perpendicular to the fibre direction, given in kpsi.

yield point
The first stress in a material, less than the maximum attainable stress, at which the strain increases at a higher rate than the stress. The point at which permanent deformation of a stressed specimen begins to take place. Only materials that exhibit yielding have a yield point.

yield strength
The stress at the yield point. The stress at which a material exhibits a specified limiting deviation from the proportionality of stress to strain.

The lowest stress at which a material undergoes plastic deformation. Below this stress, the material is elastic; above it, the material is viscous. Often defined as the stress needed to produce a specified amount of plastic deformation (usually a 0.2% change in length).

Young's modulus
The ratio of normal stress to corresponding strain for tensile or compressive stresses less than the proportional limit of the material.

See modulus of elasticity
"modulus of elasticity"

Ultimate strength in tension perpendicular to the direction of fibre orientation, given in kpsi.

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