Peak acceleration during impact with helmet materials: Effects of impactor mass and speed

Abstract The impact properties of six foam materials used for energy absorption as the liner of children's helmets, reported by Gimbel and Hoshizaki are considered further. In high-energy impacts, almost complete compression of the energy-absorbing material (bottoming out) may occur, and the severity of the impact increases greatly. Too soft a material means bottoming out occurs at low speeds, but if it is too stiff, the material itself is injurious. The fitting of equations to results in ‘no bottoming out’ and ‘bottoming out’ conditions may help assessment of what compromise is appropriate. The equations in this article correspond to peak acceleration being proportional to power functions of impactor speed and mass. 1. When there was no bottoming out, peak acceleration was found to be proportional to m ∧(c−1).v ∧(2c), with c being approximately 0.25. 2. For bottoming out, peak acceleration was found to be proportional to m ∧(p).v ∧(q), with p and q being approximately 2 and approximately 3. 3. The constants of proportionality were related to material density in a regular way.

[1]  Thomas Blaine Hoshizaki,et al.  Compressive properties of helmet materials subjected to dynamic impact loading of various energies , 2008 .

[2]  J. Devitt,et al.  MECHANISMS OF INJURY : Causes of Trauma , 1999 .

[3]  Lawrence E. Thibault,et al.  Mechanisms of impact head injury , 1994 .

[4]  Thomas Blaine Hoshizaki,et al.  The effects of impact management materials in ice hockey helmets on head injury criteria , 2009 .

[5]  David W. Lavender,et al.  Tibia Fractures: An Overview of Evaluation and Treatment , 2007, Orthopedic nursing.

[6]  J. D. Horsch.  Evaluation of occupant protection from responses measured in laboratory tests. Comments , 1987 .

[7]  G. Belingardi,et al.  Characterization of polymeric structural foams under compressive impact loading by means of energy-absorption diagram , 2001 .

[8]  Sadayuki Ujihashi,et al.  Effects of the Mechanical Properties of the Shell and Liner on the Shock Absorption of Helmets , 2006 .

[9]  K R Williams,et al.  The relationship between mass and acceleration for impacts on padded surfaces. , 1994, Journal of biomechanics.

[10]  Giuseppe Sala,et al.  Deformation mechanisms and energy absorption of polystyrene foams for protective helmets , 2002 .

[11]  J. A. Searle,et al.  The Variation of Human Tolerance to Impact and Its Effect on the Design and Testing of Automotive Impact Performance , 1978 .

[12]  T Paul Hutchinson,et al.  Pedestrian Headform Testing: Inferring Performance at Impact Speeds and for Headform Masses Not Tested, and Estimating Average Performance in a Range of Real-World Conditions , 2012, Traffic injury prevention.