IMPROVED PRESSURIZED BURST TESTING OF BALLISTIC
SELF-HEALING IN IONOMERS
S. J. Kalista, Jr. 1,2, R. A. Knepple 1 and C. W. Pillsbury 1 1
Department of Mechanical Engineering, Union College, 807 Union St, Schenectady, NY
12308 USA – e-mail: kalistas@union.edu, kneppler@garnet.union.edu,
pillsbuc@garnet.union.edu
2
Macromolecular Science and Engineering, Virginia Tech, Blacksburg, VA 24060 USA – e-mail: skalista@vt.edu
Keywords: ionomers, ballistic self-healing, EMAA, burst testing, healing efficiency ABSTRACT
The unique ballistic self-healing response expressed by poly(ethylene-co-methacrylic acid) EMAA ionomers holds unique potential for creating new and functional materials with puncture-reversal abilities. While previous testing has allowed some measure of healing ability, these have mostly been limited to qualitative observation (appearance, scar size, etc.). Consequently, no measure of healing efficiency exists for the self-healing of puncture-reversal systems. To fully characterize the healing ability and provide definitive comparisons between chemistries and systems, a method of quantitative benchmarking for puncture-healing efficiency must be developed.
While the previous pressurized burst test provided quantitative data on healed strength, its manual control yielded inaccuracy, reduced safety, and limited testing to relatively low pressures (< 35 bar). A new, automated version of this device has been fully designed and fabricated allowing burst strength to be measured in a secure and electronically-controlled fashion. Following ballistic puncture, samples are sealed within a test chamber. They are then pressurized using an air-over-water intensifier system allowing low air pressures (< 10 bar) to produce ultimate sample loads greater than 130 bar (1885 psi). A precise MATLAB/Simulink control system allows user-definable loading rates with sample pressures accurately recorded during the loading ramp and upon failure at the healed location.
The high ultimate pressures and safeguards built into this device allow measurement of both healed and undamaged films having a range of thicknesses. By comparing burst pressures of healed vs. undamaged films, this device allows the first truly quantitative measurement of healing efficiency (% strength recovery) in ballistic self-healing of ionomers. Further, its use allows continued characterization of the role of various chemistries in the self-healing of ionomers (ionic character, aging, test temperature) and provides a consistent method for measuring healing efficiency in any new and novel puncture-healing systems.
