C) Coupled Micro-Macrolevel Failure Mechanisms:

The transverse matrix cracking of a lamina as shown in Figure 6.3(c) is an important failure mechanism. The through thickness transverse crack may propagate to neighbouring lamina causing it to break.

There can be another scenario that this crack terminates at the neighboring interface. This crack front act as a stress concentration site for interface between the adjacent layer causing it to weaken, thus initiating a delamination crack in the interface. This delamination growth can lead to failure of the laminate. This is depicted in Figure 6.6(a).

A third scenario is also possible in which the transverse through thickness crack leads to interface crack in adjacent layer causing partial delamination. This delamination may cause a transverse crack in the next layer. Then this crack initiates a interfacial debonding of that layer and so on causing the failure of laminate.

The coupling between the transverse cracking of lamina and delamination is depicted in Figure 6.6(b).

Thus, the transverse cracking of lamina and delamination are strongly coupled.