| Summary: | The response of porcine adipose and skeletal muscle tissues to shock
compression has been investigated using the plate-impact technique in
conjunction with manganin foil pressure gauge diagnostics. This approach
has allowed for measurement of the levels of uniaxial stress
imparted to both skeletal muscle and rendered adipose tissue by the
shock. In addition, the lateral stress component generated within
adipose tissue during shock loading has also been investigated. The
techniques employed in this study have allowed for equation-of-state
relationships to be established for the investigated materials, highlighting
non-hydrodynamic behaviour in each type of tissue over the
range of investigated impact conditions. While the adipose tissue selected
in this work has been shown to strengthen with impact stress
in a manner similar to that seen to occur in polymeric materials, the
skeletal muscle tissues exhibited a
ow strength, or resistance to compression,
that was independent of impact stress. Both the response of
the adipose material and tested skeletal muscle tissues lie in contrast
with the shock response of ballistic gelatin, which has previously been
shown to exhibit hydrodynamic behaviour under equivalent loading
conditions.
Plate-impact experiments have also been used to investigate the
shock response of a homogenized variant of one of the investigated
muscle tissues. In the homogenized samples, the natural structure of
skeletal muscle tissue, i.e. a fibrous and anisotropic composite, was
heavily disrupted and the resulting material was milled into a fine paste. Rather than matching the response of the unaltered tissues,
the datapoints generated from this type of experiment were seen to
collapse back on to the hydrodynamic response predicted for skeletal
muscle by its linear equation-of-state (Us = 1.72 + 1.88up). This suggests
that the resistance to compression apparent in the data obtained
for the virgin tissues was a direct result of the interaction of the shock
with the quasi-organized structure of skeletal muscle.
A soft-capture system has been developed in order to facilitate
post-shock analysis of skeletal muscle tissue and to ascertain the effects
of shock loading upon the structure of the material. The system
was designed to deliver a one-dimensional,
at-topped shock pulse to
the sample prior to release. The overall design of the system was
aided by use of the non-linear and explicit hydrocode ANSYSR
AUTODYN.
Following shock compression, sections of tissue were imaged
using a transmission electron microscope (TEM). Both an auxetic-like
response and large-scale disruption to the I-band/Z-disk regions within
the tissue's structure were observed. Notably, these mechanisms have
been noted to occur as a result of hydrostatic compression of skeletal
muscle within the literature.
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