Kevin R. Hart

Continuous Self-Healing Life Cycle in Vascularized Structural Composites

J. F. Patrick Civil and Environmental Engineering Department Beckman Institute for Advanced Science and Technology University of Illinois at Urbana-Champaign Urbana , IL 61801 , USA K. R. Hart, Prof. S. R. White Aerospace Engineering Department Beckman Institute for Advanced Science and Technology University of Illinois at Urbana-Champaign Urbana , IL 61801 , USA E-mail: swhite@illinois.edu Dr. C. E. Diesendruck, Prof. J. S. Moore Chemistry Department Beckman Institute for Advanced Science and Technology University of Illinois at Urbana-Champaign Urbana , IL 61801 , USA B. P. Krull, Prof. N. R. Sottos Materials Science and Engineering Department Beckman Institute for Advanced Science and Technology University of Illinois at Urbana-Champaign Urbana , IL 61801 , USA E-mail: n-sottos@illinois.edu

Malleable and Recyclable Poly(urea-urethane) Thermosets bearing Hindered Urea Bonds

Poly(urea-urethane) thermosets containing the 1-tert-butylethylurea (TBEU) structure feature a reversible dissociation/association process of their covalent linkages under mild conditions. Unlike conventional thermosets, TBEU-based poly(urea-urethane) thermosets maintain their malleability after curing. Under high temperature (100 °C) and applied pressure (300 kPa), ground TBEU thermoset powder can be remolded to bulk after 20 min.

Automatic Optical Crack Tracking for Double Cantilever Beam Specimens

An automatic crack tracking scheme is developed for measuring the tensile opening (mode I) interlaminar fracture toughness (GIc) of continuous glass fiber-reinforced composite materials. The technique is directly compared to ASTM standard D5528, which contains a manual procedure to obtain GIc values from crack length data using a double cantilever beam (DCB) specimen. In this study, a custom computer program with edge detection software rapidly, automatically, and accurately tracks the crack front in translucent DCB specimens by optically monitoring dissimilarities between delaminated and intact portions of the sample. The program combines mechanical testing, image processing, and data collection subroutines into a single interface. The technique is compatible with sample geometries and fabrication processes described in ASTM D5528, and it requires only the addition of a charge-coupled device (CCD) and light source. Compared with the manual techniques outlined in the ASTM standard, the introduced method provides enhanced resolution and reduced workload to determine crack length and resulting GIc of continuous glass fiber-reinforced composite DCB samples.