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The major objective of this paper is to address how the actual force versus extension relationship for a seat belt during a collision is different from the one obtained at typical low rate (static) conditions. We also look at what features of the tensile stress-strain characteristic are important for the optimal performance of a seat belt. To answer these questions experimentally we use our high rate Instron -1331. We also designed an experimental set up that required special grips and contact sensors for characterizing samples of belt and yarn. In the theoretical part we demonstrate the selected rates for the tensile testing as relevant to the collisions. We also discuss the importance of the energy absorbing capacity of the belts as the most relevant characteristic of the tensile curves for this application. We then show the effect of visco-elastic factors on energy absorbing properties of fibers during collisions and the role of weaving and dyeing the belt.

A new revolutionary fiber (SECURUS™) that is offered by Honeywell to the automotive industry suitable for use in safety belts is able to absorb a passenger's kinetic energy without the passenger being subjected to excessive forces. This paper analyses thoroughly the mechanisms of the energy dissipation during an automotive accident. Such analysis shows the role of the belt and its characteristics in the process of energy dissipation. We have shown that there are two interacting mechanisms: one by the vehicle (energy absorbing elements) and another by the belt itself. We built simple and useful mathematical models of the process and showed quantitatively (using the belts of real characteristics and dimensions) how the remarkable characteristics of SECURUS™ fiber allow the force reduction. In this paper the models are simple enough to keep the major effects transparent to the observer.