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Monday, December 6, 2010

Laminate Structure and Classification in FRP

The last post we discuss about lamina and laminate terminology and definition. This post will talk about laminate classification. Laminates can be classified according to the fiber orientation :

• Unidirectional Laminate- The fiber angle in any ply is parallel to the fiber angle in every other ply. This is a thick lamina from a mechanics point of view.

• Cross Ply Laminate - The fiber angle in any ply is normal to at least one other ply and parallel to any other ply or plies (i.e., contains only 0 and 90E plies).

• Angle Ply Laminate - Fiber angle of any ply is not restricted to parallel and normal directions. These definitions have different consequences depending upon whether the fiber directions are defined by their fabrication direction or loading direction. For the purposes of composite design the fiber directions relative to the loading directions are relevant. For, instance if laminate is fabricated by laying up 0 and 90E plies, it can be used as cross ply or an angle ply laminate. Laminates can also be classified based on stacking sequence.

• Symmetric Laminate – In a symmetric laminate all plies above the midplane have the same angle as the ply in the equivalent position below the midplane (i.e., the midplane of the laminate is a plane of symmetry).

• Antisymmetric Laminate - All plies above the midplane have the opposite (negative) angle as the ply in the equivalent position below the midplane. (The midplane is a plane of antisymmetry)

• Asymmetric Laminate - The midplane is not a plane of symmetry or antisymmetry.

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