Balanced Laminate B Matrix

A 45 45 s laminate is symmetric and therefore the coupling compliance matrix b is zero.

Balanced laminate b matrix.

Contrary to angle ply laminates which are restricted to one pair of matched angles balanced laminates can contain several pairs including 0 and 90. No shear extension coupling stacking sequence does not affect a matrix both laminates above have same tensile properties same a matrix 0 90 90 0 0 90 90 0 looks like i beam when bent looks not like i beam when bent on this axis. For the unbalanced laminate the a 16 and a 26 terms are non zero. Consequently the laminate extension and bending are uncoupled.

The rectangles locate the a 16 and a 26 stiffness coefficients for each laminate. A laminate is called quasi isotropic if its extensional stiffness matrix a behaves like that of an isotropic material. For a symmetric laminate b 0 always for balanced laminates a 16 a 26 0 i e. In a balanced laminate the laminae with positive angles are balanced by equal laminae with negative angles.

A balanced laminate is one that for every θ ply in the lay up there is an equivalent θ ply in the lay up. This not only implies a11 a22 a16 a26 and a66 a11 a12 2 but also that these stiffnesses are independent of the angle of rotation of the laminate. Like angle ply laminates for balanced laminates a 16 a 26 0 and d 16 0 d. Balanced laminate balanced laminate a composite laminate in which all laminate at angles other than 0o and 90o occur only in pairs not necessarily adjacent and are symmetrical around the centerline.

The laminate is equally stiff in the transverse direction and therefore a 22 a 11. If the laminate is not balanced and symmetric macro warpage will certainly occur during cool down. An example of a balanced laminate is 0 45 45 90 45 45 0 whereas an unbalanced laminate would be 0 45. The a matrix terms shown in figure 2 define an unbalanced laminate.