Another tyre sidewall poll

It is quite possible that the failure of this tyre's structure was caused by bumping on a curve Gaz

The structure of the tyre does not simply mean the cords and wires. The rubber is part of the tyre's structure and that is what has torn.

Cuts are usually straight, or follow a uniform curve, as they are caused in one moment. A tear forms over time, and can be quite straight, but is more likely to have an irregular shape. I have also seen tears which follow a feature, such as a logo or size marking, very difficult to spot with the weight off, but opening considerably under load