Title page for ETD etd-23521427119653610

Type of Document Master's Thesis
Author Ellis, Roger L.
URN etd-23521427119653610
Title Ballistic Impact Resistance of Graphite Epoxy Composites With Shape Memory Alloy and Extended Chain Polyethylene Spectra Hybrid Components
Degree Master of Science
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Giurgiutiu, Victor
Lalande, Frederic Committee Co-Chair
Rogers, Craig A. Committee Co-Chair
  • graphite composites
  • hybrid composites
  • ballistic impact
  • SMA
  • spectra
Date of Defense 1996-12-09
Availability unrestricted
Graphite epoxy composites lack effective mechanisms for

absorbing local impact energy often resulting in penetration

and a structural strength reduction. The effect of adding

small amounts of two types of high strain hybrid

components on the impact resis tance of graphite epoxy

composites subjected to projectiles traveling at ballistic

velocities (greater than 900 ft/sec) has been studied. The

hybrid components tested include superelastic shape

memory alloy (SMA), a material having an unusually high

stra in to failure (15 - 20%), and a high performance

extended chain polyethylene (ECPE) known as Spectra™,

a polymer fiber traditionally used in soft and hard body

armor applications. A 1.2% volume fraction superelastic

SMA fiber layer was embedded on the specimens front,

middle, and backface to determine the best location for a

hybrid component in the graphite composite. From visual

observation and energy absorption values, it was c

oncluded that the backface is the most suitable location for

a high strain hybrid component. Unlike the front and middle

locations, the hybrid component is not restricted from

straining by surrounding graphite material. However, no

significant increases in energy absorption were found when

two perpendicular SMA layers and an SMA-aramid

weave configuration were tested on the backface. In all

cases, the embedded SMA fibers were pulled through the

graphite without straining to their full potential. It is believed

that this is due to high strain rate effects coupled with a

strain mismatch between the tough SMA and the brittle

epoxy resin. However, a significant increase in energy

absorption was found by adding ECPE layers to the

backface of the composite . With only a 12% increase in

total composite mass, a 99% increase in energy absorption

was observed.

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