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Research Papers

Effect of Strain Rate on the Tensile Material Properties of Human Placenta

[+] Author and Article Information
Sarah J. Manoogian

Center for Injury Biomechanics, Virginia Tech-Wake Forest, Blacksburg, VA 24061manoogsj@vt.edu

Jill A. Bisplinghoff, Craig McNally, Andrew R. Kemper, Anthony C. Santago

Center for Injury Biomechanics, Virginia Tech-Wake Forest, Blacksburg, VA 24061

Stefan M. Duma1

Center for Injury Biomechanics, Virginia Tech-Wake Forest, Blacksburg, VA 24061duma@vt.edu

1

Corresponding author.

J Biomech Eng 131(9), 091008 (Aug 07, 2009) (6 pages) doi:10.1115/1.3194694 History: Received June 25, 2008; Revised April 14, 2009; Published August 07, 2009

Automobile crashes are the largest cause of injury death for pregnant females and the leading cause of traumatic fetal injury mortality in the United States. Computational models, useful tools to evaluate the risk of fetal loss in motor vehicle crashes, are based on a limited number of quasistatic material tests of the placenta. This study presents a total of 64 uniaxial tensile tests on coupon specimens from six human placentas at three strain rates. Material properties of the placental tissue were evaluated at strain rates of 0.07/s, 0.70/s, and 7.00/s. The test data have average failure strains of 0.34, 0.36, and 0.37, respectively. Failure stresses of 10.8 kPa, 11.4 kPa, and 18.6 kPa correspond to an increase in strain rate from 0.07/s to 7.0/s. The results indicate rate dependence only when comparing the highest strain rate of 7.0/s to either of the lower rates. There is no significant rate dependence between 0.07/s and 0.70/s. When compared with previous testing of placental tissue, the current study addresses the material response to more strain rates as well as provides a much larger set of available data. In summary, tensile material properties for the placenta have been determined for use in computational modeling of pregnant occupant kinematics in events ranging from low impact activities to severe impacts such as in motor vehicle crashes.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Each placenta is sectioned into 5 mm slices

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Figure 2

(a) A steel bent stamp is used to cut the tissue into a dog bone shape, (b) the stamp provides the uniform tissue samples, (c) guide rods are used to align the stamp with the specimen, and (d) the coupon shape is cut where the tissue has a uniform consistency

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Figure 3

The specimen is mounted between two serrated grips, which are instrumented with both a load cell and an accelerometer while high-speed video records the test event

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Figure 4

The video captures of one test show a typical failure of a placental specimen pulled in uniaxial tension at 7.0/s

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Figure 5

The placenta failure stress by strain rate

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Figure 6

The placenta failure strain by strain rate

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Figure 7

The characteristic averages for each group of tests are shown together with the standard deviations of the failure values

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Figure 8

The average failure strain at each rate is shown for each donor

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Figure 9

The average failure stress at each rate is shown for each donor

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