The document discusses the design of a youth baseball helmet. It outlines the underlying issues of concussions caused by brain impact and rotational acceleration. It then describes the classical helmet design of an outer shell to distribute impact loads and foam to absorb energy. The group's innovation is to add a sensor package to detect head acceleration for parents and coaches. The document then provides materials considered for the interior and exterior of the helmet and ranks them based on their properties using an analytic hierarchy process. It presents the results of a finite element analysis.

1. Youth Baseball Helmet
Design
Group Members:
Chris Capfer
Doug Hancock
Johnna Knight
Humberto Rocha
Ben Stover

2. Underlying Phenomenon
Concussion:
● Caused by brain impacting skull due to
inertia from impact
● Rotational Acceleration is more dangerous
because it induces shear forces in brain
Classical Helmet Design:
● Outershell
○ Provides defense against initial impact
○ Prevents Linear Foam Fracture
○ Distributes Load Across large surface area
○ Reduces Abrasion on Foam
● Foam
○ Absorbs major parts of impact energy
○ Reduces acceleration of head by
increasing impact duration
Youth Baseball:
● Age 11 Baseball Players can
throw up to 70 mph
● Innovation: Add sensor package to
helmet to allow parents/coaches to
detect head acceleration

3. Merit Index Derivation

4. Materials Considered and Property Chart
Material
Tensile
Strength
(PSI)
Elastic
Modulus
(GPa)
Loss
Coefficient
Density
(lb/ft^3) Cost ($/lb)
Vinyl Nitrile 2610.68 3.47
0.01152737
752 50.56 $2.30
Expanded
Polystyrene
Foam 60.00 0.484
0.08264462
81 59.93 $5.43
PA Polyamide 12000.00 3.5
0.01142857
143 71.79 $1.85
Silicone
rubber 1305.34 0.085
0.47058823
53 143.58 $4.10
Cork 362.59 0.02 2 15.00 $2.95
Neoprene 2900.75 0.00614 6.51465798 76.78 $3.00
Polypropylene
Foam 1116.79 0.68
0.05882352
941 2.49 $0.60
Exterior Foam Lining
Material
Tensile
Strength
(PSI)
Elastic
Modulus
(GPa)
Fracture
Toughn
ess
Density
(lb/ft^3)
Cost
($/lb)
Loss
Coeffi
cient
Polyprop
ylene 0.0523 0.0810 0.6078 0.6541 1.3333 0.81
Carbon
Fiber 6.4759 2.1537 2.1151 1.1494 0.3333 0.03
Fiber
Glass 0.1110 4.3434 2.4311 1.9156 1.0000 0.02
ABS 0.0740 0.1380 0.4457 0.7404 1.0000 0.47
Polycarb
onate 0.1295 0.1428 0.4376 1.1494 1.0000 0.46
PMMA 0.1295 0.1272 0.1750 0.8166 1.6667 0.51
Polyethyl
ene 0.0278 0.0139 0.7877 0.5747 1.3333 4.70

5. Analysis Results
Interior AHP Material Selection
MATERIAL SCORE RANK
Vinyl Nitrile 0.1497 5
Expanded Polystyrene Foam 0.0668 6
PA Polyamide 0.2733 2
Silicone rubber 0.1641 3
Cork 0.1628 4
Neoprene 0.5411 1
Polypropylene Foam 0.0424 7
Exterior AHP Material Selection
MATERIAL SCORE RANK
Polypropylene 0.0841 4
Carbon Fiber 0.3652 2
Fiber Glass 0.4009 1
ABS 0.0716 5
Polycarbonate 0.0628 7
PMMA 0.0693 6
Polyethylene 0.1218 3
Finite Element Analysis

6. References
Image
1. “Concussions.” Mayfield Clinc,
mayfieldclinic.com/Images/PE-TBIfig1.jpg.
Research
1. Fernandes, F.a.o., and R.j. Alves De Sousa. “Motorcycle
helmets—A state of the art review.” Accident Analysis &
Prevention, vol. 56, 2013, pp. 1–21.,
doi:10.1016/j.aap.2013.03.011.
2. Pinnoji, P.k., et al. “Impact dynamics of metal foam shells for
motorcycle helmets: Experiments & numerical modeling.”
International Journal of Impact Engineering, vol. 37, no. 3,
2010, pp. 274–284., doi:10.1016/j.ijimpeng.2009.05.013.
3. Qiao, Pizhong, et al. “Impact Mechanics and High-Energy
Absorbing Materials: Review.” Journal of Aerospace
Engineering, vol. 21, no. 4, 2008, pp. 235–248.,
doi:10.1061/(asce)0893-1321(2008)21:4(235).
4. Robinson, Matthew B., et al. “Reducing effect of softball-to-
Head impact by incorporating slip-Surface in helmet.”
Procedia Engineering, vol. 13, 2011, pp. 415–421.,
doi:10.1016/j.proeng.2011.05.107.
5. Schwizer, Patrick, et al. “Evaluation of Catcher Mask
Impacts.” Procedia Engineering, vol. 147, 2016, pp. 228–
233., doi:10.1016/j.proeng.2016.06.218.