Elastic Behaviour of Laminates

Question 1

What are the 3 special cases where normal stresses give no shear strain?

Answer 1

• Along the fibres
• Perpendicular
• One intermediate angle.
  (any other angle give shear).

Question 2

What happens when stress is applied in the plane of the laminate?

Answer 2

Produce no out - of plane bending or twisting.

(Need reflectional symmetry about the mid-plane).

Question 3

How are balanced lamination created?

Answer 3

• Where normal stresses give no shear strain (and vice versa).
• Need to have 6, 8, 10 symmetry to directions of layer.

6 folds = 0 / 60 / 120 deg
8 folds = 0 / 45 / 90 / 135 deg
^^^these are balanced

• 0 /90 deg is not balanced.