Stefano Signetti1, Marco Nicotra2, Martino Colonna3, Nicola M Pugno4. 1. Laboratory of Bio-Inspired and Graphene Nanomechanics, Department of Civil, Environmental and Mechanical Engineering, University of Trento, Italy. 2. Department of Civil, Chemistry, Environmental and Materials Engineering, University of Bologna, Italy. 3. Department of Civil, Chemistry, Environmental and Materials Engineering, University of Bologna, Italy. Electronic address: martino.colonna@unibo.it. 4. Laboratory of Bio-Inspired and Graphene Nanomechanics, Department of Civil, Environmental and Mechanical Engineering, University of Trento, Italy; School of Engineering and Materials Science, Queen Mary University of London, UK; Ket-Lab, Edoardo Amaldi Foundation, Italian Space Agency, Italy. Electronic address: nicola.pugno@unitn.it.
Abstract
OBJECTIVES: Winter sports are high-energy outdoor activities involving high velocities and acrobatic maneuvers, thus raising safety concerns. Specific studies on the impact mechanics of back protectors are very limited. In this study analytical and numerical models are developed to rationalize results of impact experiments and propose new design procedures for this kind of equipment. DESIGN: Different soft-shell solutions currently available on the market are compared. In particular, the role of dynamic material constitutive properties and of environmental temperature (which affects mainly material stiffness) on energy absorption capability are evaluated. METHODS: Starting from dynamic mechanical-thermal characterization of the closed-cell polymeric foams constituting the protectors, we exploited analytical modeling and Finite Element Method simulations to interpret experimental data from drop weight impact test and to characterize protectors at different temperatures and after multiple impacts. RESULTS: The temperature and frequency dependent properties of these materials characterize their impact behavior. Modeling results are in good agreement with impact tests. Results demonstrate how ergonomic soft-shell solution provides an advantage with respect to traditional hard-shell in terms of impact protection. Moreover, it can maintain nearly unaltered its protective properties after multiple impacts on the same point. CONCLUSIONS: The coupled analytical-simulation approach here presented could be extensively used to predict the impact behavior of such equipment, starting from material characterization, allowing to save costs and time for physical prototyping and tests for design and optimization.
OBJECTIVES: Winter sports are high-energy outdoor activities involving high velocities and acrobatic maneuvers, thus raising safety concerns. Specific studies on the impact mechanics of back protectors are very limited. In this study analytical and numerical models are developed to rationalize results of impact experiments and propose new design procedures for this kind of equipment. DESIGN: Different soft-shell solutions currently available on the market are compared. In particular, the role of dynamic material constitutive properties and of environmental temperature (which affects mainly material stiffness) on energy absorption capability are evaluated. METHODS: Starting from dynamic mechanical-thermal characterization of the closed-cell polymeric foams constituting the protectors, we exploited analytical modeling and Finite Element Method simulations to interpret experimental data from drop weight impact test and to characterize protectors at different temperatures and after multiple impacts. RESULTS: The temperature and frequency dependent properties of these materials characterize their impact behavior. Modeling results are in good agreement with impact tests. Results demonstrate how ergonomic soft-shell solution provides an advantage with respect to traditional hard-shell in terms of impact protection. Moreover, it can maintain nearly unaltered its protective properties after multiple impacts on the same point. CONCLUSIONS: The coupled analytical-simulation approach here presented could be extensively used to predict the impact behavior of such equipment, starting from material characterization, allowing to save costs and time for physical prototyping and tests for design and optimization.