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Laminates of Orthotropic pliesSection 2.4.3 for in-plane loading onlyHookes law for k-th ply

Stress resultants

A Matrix

Effective propertiesFrom Qs to As using lamination parameters

Effective properties

Hookes law with effective propertiesAverage stresses

Hookes law

Typical stiffness optimization problemNo stresses in individual plies, so no credible failure constraint.

When 0-deg, 90-deg and 45-deg plies are present this is reasonable even for strength.

Example 4.1.1

Sanity checks for first two laminates