Identification

A "perfect" impact protection should present a triphasic mechanical behaviour. The second phase called plateau is the most important one as it represents a constant stress for a large strain range.

To obtain this plateau, non-linear mechanisms must happen within the material. Considering stochastic foams that are classical shock absorbers, the main mechanisms arise from the bending of the struts and walls: buckling (elastomeric foams), buckling then plastic hinges (elasto-plastic foams) or fracture (fragile foams like ceramic foams).

With the developpement of new manufacturing processes like additive manufacturing, heterogeneous hierarchical structurations can be produced. The strain mechanisms happening inside these materials become very diverse. However, to be able to drive the conception of those new and more complex materials, a deep understanding of these mechanisms, their interactions and how they evolve with the strain rate is needed.