Richards Stuff

Question 1

3 assumptions of whole ABD matrix type method

Answer 1

1. thin plate assumptions are made
2. plane sections remain plane (no shear deformation)
3. perfect layer bonding

Question 2

Why are +45 deg / -45 deg layers are positioned next to eachother and at surface

Answer 2

• at surface to increase damage tolerance
• next to eachother to reduce elastic bend-twist coupling

Question 3

5 stacking sequence rules for composite lamina

Answer 3

1. Fibre angles are normally restricted to 0°, 90°, +45° and -45°.
2. For most practical purposes, laminates are both balanced (i.e. they have as
   many +45° layers as they have -45° layers) and symmetric about their midplane.
3. Grouping of more than 3 layers of the same orientation is not normally
   permitted - to avoid large inter-lamina stresses.
4. A +45°/-45° pair is normally positioned at the surface to increase damage
   tolerance.
5. +45° and -45° layers are usually placed next to each other in order to minimise
   elastic bend-twist coupling.