Composite Failure Criteria
Laminate Failure
To determine whether a laminate will fail due to applied loading, the
program first calculates stresses across the different plies. It next
applies a failure criterion based on these stress levels using a failure
theory. A laminate is considered to fail when a first ply or a first group
of plies fails.
Failure of composites occurs in multiple steps. When stress in the first
ply or a first group of plies is high enough, it fails. This point of
failure is the first ply failure (FPF) beyond which a laminate can still
carry the load. For a safe design, laminates should not experience stress
high enough to cause FPF. The point where the total failure occurs is
termed the ultimate laminate failure (ULF). Failure of composites occurs
on a micromechanical scale due to fiber damage, matrix cracking, or interface
or interphase failure. These local failure modes cannot predict global
laminate failure satisfactorily.
Composite failure theories predict global laminate failure. These failure
theories can be interactive, non-interactive or partially interactive.
The non-interactive theories do not consider the interaction between different
stress components, whereas the interactive theories do.
The three theories available for laminate failure criteria are:
See here
for Guidelines
for Selecting a Failure Criterion.
Related Topic
Composite
Shells