Effect of dynamic loading on the brittle behavior of biomaterial microstructure - Response of nutshell under dynamic compression

This study presents the mechanical response of hazelnut shells under compressive loadings at different velocities with regards to their microstructure. The hazelnuts were loaded with a testing machine and a flywheel to impose quasistatic and dynamic compressions. The macroscopic response of the shell is typical of an elastic-brittle behavior. The influence of the strain rate at constant moisture was highlighted by considering macroscopic mechanical characteristics such as maximum force, shell stiffness and energy dissipated to failure. SEM observations of the fracture surface revealed the shell microstructure constituted of microscopic sclereids. These observations demonstrated that the crack propagated by shearing sclereids or by cracking their interfaces. This study highlights that the damage propagation in the microstructure depends on the velocity of the compression.