Composite Materials

· The layers of a laminate interact to produce complex stress distributions when the composite is simply loaded.
· The diagram shows the stresses in two layers of a cross-ply composite subjected to a uniaxial tensile stress, σ_1C , parallel to the fibers in lamina 1.

· Due to this stress and constraints from lamina 2, lamina 1 sees a tensile stress in the parallel direction, ¹σ₁ = 1.82 σ_1C , and a tensile stress normal to the fibers, ¹σ₂ = 0.037 σ_1C .
· Lamina 2 has its fiber direction normal to those in lamina 1 and experiences a tensile stress normal to its fibers, ²σ₂ = 0.18 σ_1C , and a compressive stress, ²σ₁ = -0.037 σ_1C , parallel to the fibers.

From: Hull,
"Introduction to Composite Materials,"
Cambridge (1992)