#### 5.4.2.1. Laminate Stiffness and Compliance Matrices

The laminate stiffness matrix is an 8 x 8 matrix that contains the ABD matrix (6 x 6) as well as the shear matrix C (2 x 2).

| (5–126)

The ABD matrix of the laminate is the stiffness matrix of the laminate. A is the in-plane stiffness matrix, B describes the coupling between in-plane forces and bending moments and D is the flexural stiffness matrix. The B matrix becomes 0 in the case of a symmetrically balanced laminate.

In addition to the ABD terms the shear matrix C is evaluated as well. The shear matrix has form

and represent the and stiffness, respectively.

The compliance matrix is an 8 x 8 matrix that contains the inverse of the ABD matrix and the inverse of the C matrix. The inverse of the ABD is also called the abd matrix (ABD -1).

Figure : Relation Between ABD Matrix and the Coupling Between Laminate Forces and Deformations

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