5. Mechanical properties. Changes during aging

For structural CMOs, it is the mechanical properties that determine sizing, and changes in these properties are taken into account in safety factors (in-use certification).

However, when optimizing the strength of industrial structures, the aim is not to minimize the values of the failure criteria, but to minimize the distribution of the CMO mass at a given criterion value. For reasons of production cost, we'll be looking for the most constant part thickness possible, with symmetrical stacking of plies and continuity in their orientation.

As materials age, they undergo damage phenomena which, in addition to accidental impact, lead to delamination (the weak point of CMOs), and correspond to creep and fatigue. These aging factors are superimposed on the effects induced by temperature and humidity, and set the limits for a material's use....