The characterization of soft or low impedance materials is of increasing importance as these materials are now commonly used in impact and energy absorbing applications, particularly for vehicle safety and crashworthiness. Advanced numerical models to improve safety require high rate material properties for soft materials, where the mode of loading is predominantly compressive and large deformations may occur at high rates of deformation. Importantly, the competing effects of material impedance, specimen size, and rate of loading must be addressed to accurately determine the material properties of these soft materials. The investigation of injury mechanisms in auto crash requires the integration of numerical human body and vehicle models. Key to this integration and coupling of the loading is the implementation of an appropriate seat model, including appropriate dynamic material properties for the seat foam. Although seat foam is primarily selected and designed for comfort it also acts as a means of load distribution, therefore, playing a vital role in coupling the occupant and vehicle during collisions. The material properties of five common automotive seat foams have been measured under quasi-static conditions, and at high strain rates using a Polymeric Split Hopkinson Pressure Bar apparatus. The foam materials exhibit typical mechanical response, with increasing stiffness roughly corresponding to increasing material density, and show little to no rate sensitivity until the material is consolidated. The quasi-static and high deformation rate material properties have been successfully implemented in a common foam constitutive model and verified using an explicit finite element model.
High rate characterization of automotive seat foams
Hochgeschwindigkeitskennzeichnung von Fahrzeugsitz-Schaumstoffen
2007
11 Seiten, 13 Quellen
Aufsatz (Konferenz)
Englisch
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