Bicycle helmet foam liners absorb energy during impacts. Our goal was to determine if the impact attenuation properties of expanded polystyrene (EPS) foam used in bicycle helmets change with age. Foam cores were extracted from 63 used and unused bicycle helmets from ten different models spanning an age range of 2–20 yrs. All cores were impact tested at a bulk strain rate of 195 s−1. Six dependent variables were determined from the stress–strain curve derived from each impact (yield strain, yield stress, elastic modulus, plateau slope, energy at 65% compression, and stress at 65% compression), and a general linear model was used to assess the effect of age on each dependent variable with density as a covariate. Age did not affect any of the dependent variables; however, greater foam density, which varied from 58 to 100 kg/m3, generated significant increases in all of the dependent variables except for yield strain. Higher density foam cores also exhibited lower strains at which densification began to occur, tended to stay within the plateau region of the stress–strain curve, and were not compressed as much compared with the lower density cores. Based on these data, the impact attenuation properties of EPS foam in field-used bicycle helmets do not degrade with the age.

References

References
1.
ASTM International
,
2010
, “
Standard Specification for Helmets Used for Downhill Mountain Bicycle Racing, F1952-10
,”
ASTM International
,
West Conshohocken, PA
.
2.
Consumer Product Safety Commission
,
1998
, “
Safety Standard for Bicycle Helmets; Final Rule
,”
16 CFR Part 1203
, Consumer Product Safety Commission, Washington, DC.
3.
AS/NZS 2063
,
2008
, “
Bicycle Helmets
,”
Standards Australia, Sydney/NSW and Standards New Zealand
,
Wellington, New Zealand
.
4.
Snell
,
2000
, “
1995 Standard for Protective Headgear—1998 Revision—For Use in Bicycling
,”
Snell Memorial Foundation
,
North Highlands, CA
.
5.
Liu
,
D.-S.
,
Chang
,
C.-Y.
,
Fan
,
C.-M.
, and
Hsu
,
S.-L.
,
2003
, “
Influence of Environmental Factors on Energy Absorption Degradation of Polystyrene Foam in Protective Helmets
,”
Eng. Failure Anal.
,
10
(
5
), pp.
581
591
.
6.
Mills
,
N. J.
, and
Gilchrist
,
A.
,
1991
, “
The Effectiveness of Foams in Bicycle and Motorcycle Helmets
,”
Accid. Anal. Prev.
,
23
(
2–3
), pp.
153
163
.
7.
Mills
,
N. J.
, and
Gilchrist
,
A.
,
2006
, “
Bicycle Helmet Design
,”
Proc. Inst. Mech. Eng., Part L
,
220
(
4
), pp.
167
180
.
8.
Di Landro
,
L.
,
Sala
,
G.
, and
Olivieri
,
D.
,
2002
, “
Deformation Mechanisms and Energy Absorption of Polystyrene Foams of Protective Helmets
,”
Polym. Test.
,
21
(
2
), pp.
217
228
.
9.
Gibson
,
L. J.
, and
Ashby
,
M. F.
,
1997
,
Cellular Solids: Structure and Properties
,
2nd ed.
,
Cambridge University Press
,
Cambridge, UK
.
10.
Ouellet
,
S.
,
Cronin
,
D.
, and
Worswick
,
M.
,
2006
, “
Compressive Response of Polymeric Foams Under Quasi-Static, Medium and High Strain Rate Conditions
,”
Polym. Test.
,
25
(
6
), pp.
731
743
.
11.
Maji
,
A. K.
,
Schreyer
,
H. L.
,
Donald
,
S.
,
Zuo
,
Q.
, and
Satpathi
,
D.
,
1995
, “
Mechanical Properties of Polyurethane-Foam Impact Limiters
,”
J. Eng. Mech.
,
121
(
4
), pp.
528
541
.
12.
Nagy
,
A.
,
Ko
,
W. L.
, and
Lindholm
,
U. S.
,
1974
, “
Mechanical Behavior of Foamed Materials Under Dynamic Compression
,”
J. Cell. Plast.
,
10
(
3
), pp.
127
134
.
13.
Thomas
,
T.
,
Mahfuz
,
H.
,
Carlsson
,
L. A.
,
Kanny
,
K.
, and
Jeelani
,
S.
,
2002
, “
Dynamic Compression of Cellular Cores: Temperature and Strain Rate Effects
,”
Compos. Struct.
,
58
(
4
), pp.
505
512
.
14.
Kockott
,
D.
,
1989
, “
Natural and Artificial Weathering of Polymers
,”
Polym. Degrad. Stab.
,
25
(
2–4
), pp.
181
208
.
15.
Andrady
,
A. L.
, and
Pegram
,
J. E.
,
1991
, “
Weathering of Polystyrene Foam on Exposure in Air and in Seawater
,”
J. Appl. Polym. Sci.
,
42
(
6
), pp.
1589
1596
.
16.
White
,
J. R.
, and
Turnbull
,
A.
,
1994
, “
Weathering of Polymers: Mechanisms of Degradation and Stabilization, Testing Strategies and Modelling
,”
J. Mater. Sci.
,
29
(
3
), pp.
584
613
.
17.
Xu
,
T.
,
Li
,
G.
, and
Pang
,
S.-S.
,
2011
, “
Effects of Ultraviolet Radiation on Morphology and Thermo-Mechanical Properties of Shape Memory Polymer Based Syntactic Foam
,”
Composites, Part A
,
42
(
10
), pp.
1525
1533
.
18.
Pearsall
,
D. J.
, and
Dowler
,
P. M.
,
2008
, “
A Longitudinal Study of Ice Hockey Helmet Shelf Life
,”
J. ASTM Int.
,
5
(
8
), pp.
1
5
.
19.
Pearsall
,
D. J.
,
Lapaine
,
P.
, and
Ouckama
,
R.
,
2015
, “
Ten Years Later: Ice Hockey Helmet Impact Mechanics Change With Age
,”
Proc. Inst. Mech. Eng., Part P
(in press).
20.
Mills
,
N. J.
, and
Gilchrist
,
A.
,
2008
, “
Oblique Impact Testing of Bicycle Helmets
,”
Int. J. Impact Eng.
,
35
(
9
), pp.
1075
1086
.
21.
Gale
,
A.
, and
Mills
,
N. J.
,
1985
, “
Effect of Polystyrene Foam Liner Density on Motorcycle Helmet Shock Absorption
,”
Plast. Rubber Process. Appl.
,
5
, pp.
101
108
.
22.
de Sousa
,
R. A.
,
Goncalves
,
D.
,
Coelho
,
R.
, and
Teixeira-Dias
,
F.
,
2012
, “
Assessing the Effectiveness of a Natural Cellular Material Used as Safety Padding Material in Motorcycle Helmets
,”
Simulation
,
88
(
5
), pp.
580
591
.
23.
Asiminei
,
A. G.
,
Bosche
,
K. V.
,
Van der Perre
,
G.
,
Verpoest
,
I.
, and
Goffin
,
J.
,
2008
, “
An Approach to Model the Head-Bicycle Helmet Dynamic Behaviour Through Transient Finite Element Analysis
,”
15th Finite Element Workshop, The Finite Element Method in Biomedical Engineering, Biomechanics and Related Fields
,
Ulm, Germany
, July 16–17.
24.
Fernandes
,
F. A. O.
,
de Sousa
,
R. J. A.
,
Willinger
,
R.
, and
Deck
,
C.
,
2013
, “
Finite Element Analysis of Helmeted Impacts and Head Injury Evaluation With a Commercial Road Helmet
,”
International Research Council on the Biomechanics of Injury
(
IRCOBI
) Conference, Gothenburg, Sweden, Sept. 11–13, Paper No. IRC-13-48.
25.
Mills
,
N. J.
, and
Gilchrist
,
A.
,
2008
, “
Finite-Element Analysis of Bicycle Helmet Oblique Impacts
,”
Int. J. Impact Eng.
,
35
(9), pp.
1087
1101
.
26.
Kroeker
,
S. G.
,
Bonin
,
S. J.
,
DeMarco
,
A. L.
,
Good
,
C. A.
, and
Siegmund
,
G. P.
,
2014
, “
Does Age Affect the Impact Properties of Helmet Foam Liners?
,”
World Congress of Biomechanics
,
Boston, MA
, July 6–11.
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