Energy Dispersion of Variable Stiffness Structures

This study regarding a proposed variable stiffness structure will focus on structure geometry as a proof of concept attempt to develop a new design for energy dispersion. The structure was designed such that as a greater force is experienced, more of the structure comes into contact with itself making the structure stiffer, hence the name variable stiffness structure. This variable stiffness will provide softer structure properties under small loads and stiffer properties under larger loads. This allows an impact to be absorbed by the structure under low loads without compromising structure stiffness that provides protection at higher loads. Intended function of this structure is an intermediate layer in protective gear such as helmets for military and athletic applications, athletic padding, or everyday applications such as the soles of shoes or medical crutches. Proof of concept for the variable stiffness structures was successful as validated by the observance of three distinct slopes in the load vs. compression data reflecting the desired three contact regions on four different structures tested. Structures that performed as intended were also more successful at dispersing energy as calculated by the integral of the load vs. compression curves. Observed trends include desirable increased contact spacing and geometry thickness for a 2:1 height to width structure ratio. Since these results are on the limits of the optimization conditions, additional testing will be required to determine true optimal design. Energy dispersion trends would suggest that structure 135 was the most successful structure at dissipating energy. While this structure was successful, (1.42 J of energy dissipated in the variable stiffness region) structure 313 outperformed it by nearly 1 J (2.25 J average). Upon examination of testing footage, structure 313 displayed the unique quality of engaging multiple contact points in each contact region. This suggests that the number of contact points may be the unobserved variable that will further the variable stiffness structure design for improved energy dispersion in future iterations. With further development, the variable stiffness structures could be an influential means of energy dispersion for utilization in a wide variety of applications.