The laminate engineering constants are derived from the normalized compliance matrices which can be compared with the ply compliance matrix. Therefore the in-plane engineering constants are derived from the normalized in-plane compliance matrix:
Laminate stiffness:
Laminate stiffness:
Laminate shear stiffness:
and the out-of-plane shear terms are derived from the normalized shear compliance matrix:
Shear correction factors:
and k55
Out-of-plane shear stiffness:
Out-of-plane shear stiffness:
And the flexural constants are derived from the normalized flexural compliance matrix:
Flexural laminate stiffness:
Flexural laminate stiffness:
Flexural laminate shear stiffness:
In the case of coupling between in-plane and bending forces
(
matrix has non-zero elements),
the engineering constants represents the case where the laminate is
free to curve when loaded with in-plane forces.