Composite Materials 
Given the material properties of a unidirectional lamina, this calculator constructs the stiffness matrix [C] and the compliance matrix [S] of the lamina in the principal directions. If the angle of rotation of the lamina is given (other than 0 degree), this calculator also constructs the stiffness matrix [] and the compliance matrix [] in the rotated directions.

StressStrain Relations for Lamina for Principal Directions  
The stiffness matrix [C] in the principal directions is
The compliance matrix [S] in the principal direction is

Coordinate Transformation Matrix  
The coordinate transformation matrix is
The engineeringtensor interchange matrix [R] is 
Stiffness and Compliance Matrices for Angled Lamina  
The stiffness matrix for a lamina of arbitry orient can be expressed in terms of the stiffness matrix in the principal direction,
The complicance matrix for a lamina of arbitry orient can be obtained in a similar manner.
