Quiz: Section 5.3 Failure Criterion for Laminate

1. The degradation of the stiffness and strength properties of each failed lamina depends on the philosophy followed by the user. Which philosophy will give a more conservative value of load for failure?

When a ply fails, fully discount the ply and replace with a ply of near zero stiffness and strength.

When a ply fails, it may have cracks parallel to the fibers. This ply is still capable of taking load parallel to the fibers. Here, the cracked ply can be replaced by a hypothetical one with no transverse stiffness, transverse tensile strength, and shear strength. The longitudinal modulus and strength remain unchanged.

2. Let’s suppose you have a 3-ply laminate under an axial load. You find out the first ply-failure takes place in the top layer at the axial load of N_x=1000lbs/in. Your next step would be to degrade the top ply. What load do you apply for figuring out the next ply failure?

1000 lb/in

2000 lb/in

1 lb/in

3. If one ply fails in a laminate, does the entire laminate fail?

Maybe

Yes

4. What is the failure called when the whole laminate is considered to be failed?

Second ply failure

First ply failure

Last ply failure

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