A wearable hydraulic shock absorber with efficient energy dissipation

Abstract

Advances in shock absorber technology are often translated to wearable personal protective equipment (PPE) to protect humans from impact-related injuries. However, the effectiveness of PPE is limited by factors such as the tolerable size and weight of the PPE device and the environmental conditions in which the PPE will be used. In this study, we leveraged the energy dissipation of fluid flow using soft structures to prototype a novel, wearable hydraulic shock absorber — the Soft Hydraulic Shock. The Soft Hydraulic Shock achieved an efficient energy absorption ratio of 100 % across a range of impact loading conditions due to its fluid-based mechanism of energy absorption. In comparison, five state-of-the-art shock-absorbing technologies with similar dimensions and weights used in American football helmets were found to have average energy absorption ratios ranging from 74.0 % to 90.0 %, on average. Furthermore, the Soft Hydraulic Shock maintained a stable energy dissipation across a wide range of temperatures (-18 °C, 19.5 °C, 50 °C), while the energy dissipation of other shock absorbing technologies varied up to 20 % across these temperatures. Analyses of the behavior of the Soft Hydraulic Shock with different design parameters and impact loadings were further explored with a validated finite element model of the device. Finally, the Soft Hydraulic Shock demonstrated the ability to significantly mitigate brain injury risk (average 23.9 % reduction in Head Acceleration Response Metric) when implemented into a full helmet system. The results of this study demonstrate the promise of wearable hydraulic shock absorbers and provide a platform for further optimizing their performance.