Optimization

The angle between fiber direction and the tensile load will affect the stiffness of the composite layer. The stiffness and strength are higher if the maximum tensile load acts along the fibers.

Stiffness of a fabric depends upon the load angle. An angle of 45^o corresponds to minimum rigidity. Stiffness of straight fibers is higher than that for curved ones.

Fracture of a multi-directional laminate is a multi-stage process. First, the microstructural interlayer damage will take place at the edge of plate.

Interlayer shear stress causes a coupling effect. The figure shows the cross sectional areas of original and deformed plates.

Multi-oriented laminate [0^o/45^o/90^o/135^o/...]_s has better notch resistance than a laminate with a lower variety of fiber orientation [0^o/90^o]_s.

Tangential stress in the pressure vessel is twice as large as radial stress. The stress ratio defines the optimal angle of two-directional lay-up: 55^o.

The optimal lay-up direction is coincident with the direction of the maximum inner force.

An optimum honeycomb composite skin structure will have symmetrical stacking and its 0-oriented laminae will be placed along the direction of the maximum tensile stress at external surfaces.