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Research Papers: FORMING

Thermoforming and Structural Analysis of Combat Helmets

[+] Author and Article Information
Bruce K. Cartwright

Pacific Engineering Systems International,
277-279 Broadway,
Glebe, New South Wales 2037, Australia
e-mail: brucec@esi.com.au

N. Lex Mulcahy

Pacific Engineering Systems International,
277-279 Broadway,
Glebe, New South Wales 2037, Australia
e-mail: lexm@esi.com.au

Allen O. Chhor

Pacific Engineering Systems International,
277-279 Broadway,
Glebe, New South Wales 2037, Australia
e-mail: allenc@esi.com.au

Stuart G. F. Thomas

Defence Materials Technology Centre Limited,
Level 2, 24 Wakefield Street,
Hawthorn, Victoria 3122, Australia
e-mail: stuart.thomas@vcamm.com.au

Madhusudan Suryanarayana

Defence Materials Technology Centre Limited,
Level 2, 24 Wakefield Street,
Hawthorn, Victoria 3122, Australia
e-mail: madhusudan.suryanarayana@deakin.edu.au

James D. Sandlin

Defence Materials Technology Centre Limited,
Level 2, 24 Wakefield Street,
Hawthorn, Victoria 3122, Australia
e-mail: james.sandlin@vcamm.com.au

Ian G. Crouch

Defence Materials Technology Centre Limited,
Level 2, 24 Wakefield Street,
Hawthorn, Victoria 3122, Australia
e-mail: ianarmoursolutions@gmail.com

Minoo Naebe

Defence Materials Technology Centre Limited,
Level 2, 24 Wakefield Street,
Hawthorn, Victoria 3122, Australia
e-mail: minoo.naebe@deakin.edu.au

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING. Manuscript received December 20, 2014; final manuscript received July 24, 2015; published online September 4, 2015. Assoc. Editor: Yannis Korkolis.

J. Manuf. Sci. Eng 137(5), 051011 (Sep 04, 2015) (9 pages) Paper No: MANU-14-1688; doi: 10.1115/1.4031154 History: Received December 20, 2014; Revised July 24, 2015

To reduce combat casualties, military helmets are designed to provide protection against projectiles. Modern combat helmets are constructed of relatively lightweight composite materials that provide ballistic protection to the soldier. The manufacture of most composite helmets is labor intensive and involves the manual application and smoothing of individual layers of reinforcement to a concave mold surface. The recently developed double diaphragm deep drawing thermoforming process turns as-purchased, flat-form composite materials into structurally efficient three-dimensional shapes. Using this process, prototype shells have been produced and subsequently tested structurally. The success of the outcome has been greatly assisted through the use of specialized virtual prototyping techniques to provide insight into the thermoforming process of the shells and subsequently their structural performance by accounting for the actual fiber orientations of those finished shells.

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Figures

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Fig. 1

Numerical model of a flexure test

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Fig. 2

The numerical modeling of the initial process variables showed that wrinkles were likely to develop in the formed part. This was confirmed by experiment.

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Fig. 3

Varying the process parameters in the simulations enabled the conditions for a wrinkle-free helmet to be developed

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Fig. 4

Angles through which the fibers were sheared due to the forming process

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Fig. 5

FE model of lateral compression test setup

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Fig. 6

Spectra Shield SR-3136 helmet produced from the newly commissioned preproduction prototype D4 machine

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Fig. 7

Spectra Shield II SR-3130 helmet shell in test jig: (a) vertical compression and (b) lateral compression

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Fig. 8

Force against displacement for side-to-side compression of the helmet—test, the analysis with assumed-orthogonal fiber directions and the analysis with formed fiber directions

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Fig. 9

Spectra Shield 3136 ply damage

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Fig. 10

Tied interface stress–displacement curve

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