Dr. Kenneth M. Liechti  
Professor of Aerospace Engineering and Engineering Mechanics

Research Center for Mechanics of Solids, Structures & Materials

 
 
 
 
 
 

INTERFACIAL CRACK GROWTH AT GLASS EPOXY INTERFACES
Crack opening interferometry reveals that crack growth occurs via lateral sperading of voids along the original front Atomic force microscopy reveals ridges left on the epoxy fracture surface.  The ridges are the ligaments left behind by the lateral propagation of the void.
More complex patterns under mixed-mode bonding

 
 

MIXED MODE RUBBER/METAL DEBONDING
Stationary
Opening mode fracture at different loading rates
Initial Normal Load
Initiation
Propagation
Mixed-mode loading with positive shear
Initial Normal Load
Initiation
Propagation
Mixed-mode loading with negative shear






Brief Narrative

Dr. Kenneth M. Liechti, Professor of Aerospace Engineering and Engineering Mechanics

Professor Liechti received a B.Sc. degree in Aeronautical Engineering with first class honors in 1973 from Glasgow University in Scotland. His graduate degrees are from the California Institute of Technology (M.S. 1974 and Ph.D. 1980). He worked for General Dynamics' Fort Worth Division for two years and then joined the University of Texas at Austin in September 1982. He was promoted to Associate Professor in 1987 and Professor in 1992.

Dr. Liechti's major technical interests are in the mechanics of solids with an emphasis on fracture at interfaces between materials, fracture in adhesively bonded joints and the mechanical behavior of thin films. Research problems in these areas are approached via a combination of experiments and numerical analysis. The topics are usually motivated by practical problems such as the durability of adhesively bonded joints in automobile structures that are exposed to solvents, the durability of interfaces in microelectronic devices, debonding in rubber to metal joints and delamination in sandwich structures at high temperatures.

Dr. Liechti's work on fracture at glass/epoxy interfaces is directed towards understanding how fracture mechanisms occur at the micro and nano scales. The latter has been probed using atomic force microscopy. Associates in Chemistry and he and are currently working to develop probes that will help us understand how the mechanical behavior of adhesives changes as the interface is approached. In the work on the fracture of adhesively bonded joints, Dr. Liechti and his students have developed a number of mixed-mode fracture property specimens. These have been and are being incorporated in several industries along with design guidelines and procedures. Dr. Liechti has acted as a consultant to several companies that deal with adhesion problems.

Education:

Ph.D. Aeronautics, June 1980, California Institute of Technology.
M.S. ,Aeronautics, June1974, California Institute of Technology.
B.Sc. First Class Honors in Aeronautical Engineering, June 1973, Glasgow University, Scotland, UK. Academic Positions: 1992-present Professor, Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin.
9/87-8/92 Associate Professor, Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin.
9/82-8/97 Assistant Professor, Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin. Other Professional Experience: 5/80-8/82 Research Scientist, General Dynamics' Fort Worth Division, Fort Worth, TX.
6/74-9/74 Engineer, Jet Propulsion Laboratory, Pasadena, CA.
6/73-9/73 Engineer, United Technologies, Chemical Systems Division, Sunnyvale, CA. Honors and Awards: Elected, Fellow of the American Society of Mechanical Engineers, 1998
ASE/EM Faculty Teaching Award, 1992
Robert & Francis Stark Centennial Fellowship in Engineering, 1991
Engineering Faculty Foundation Award, 1990
Schuster Marlar Award, California Institute of Technology, 1980
Gray, Law and Watt Scholarship, University of Glasgow, 1973-1976 Editorial Boards: Experimental Mechanics National Committees: July 1997-Present ASME, Applied Mechanics Division, Chair of the Experimental Mechanics Technical Committee. July 1995-July 1997 ASME, Applied Mechanics Division, Secretary of the Experimental Mechanics Technical Committee. Research Interests: Adhesion, Fracture Mechanics, Composites, Solid Mechanics. Current Projects: Durability of Automotive Adhesively Bonded Joints
Time-dependent Fracture of Rubber to Metal Joints
Delamination Mechanics of Printed Wiring Boards
Crack Nucleation from Bimaterial Corners
Compressive Delamination of High Temperature Sandwich Structures Publications

Xu, D., Ravi-Chandar, K., and Liechti, K. N., "On scale dependence in friction: Transition from intimate to monolayer lubricated contact," Journal of Interface and Colloid Science, accepted 2007.

Xu, D., Liechti, K. M. and Ravi-Chandar, K (2007) "Mesoscale scanning probe tips with subnanometer rms roughness," Review of Scientific Instruments,  Vol. 78, -DOI: 10.1063/1.2756997.

Xu, D., Liechti, K. M. and Ravi-Chandar, K., "On the modified Tabor parameter for the JKR-DMT transition in the presence of a liquid meniscus," Journal of Interface and Colloid Science, Vol. 315, pp. 772-785, 2007.

Wang, M., Xu, D.,  Ravi-Chandar, K., and Liechti, K. M., "On the development of a Meso Scale Friction Tester" Experimental Mechanics, Vol. l47 (1), pp. 123-132, 2007.

Park, S-J., Liechti, K. M. Roy, S., "A Nonlinear Viscoelastic Fracture Analysis of Concrete/FRP Delamination in Aggressive Environments," International Journal of Fracture, Vol. 149, pp. 9-27, 2006.

Chakkarapani, V., Ravi-Chandar, K., and Liechti, K. M., "Characterization of Multiaxial Constitutive Properties of Rubbery Polymers," J. Eng. Mater. Technol., Vol. 128, p. 489, 2006.

Roy, S., Wang, Y., Park, S., and Liechti, "Cohesive Layer Modeling of Time-Dependent Debond Growth in Aggressive Environments," Journal of Engineering Material and Technology, Vol. 128, No. 1, pp. 11-17, 2006.

Xu, D., Liechti, K. M., de Lumley Woodyear, T., "Closed Form Nonlinear Analysis of the Peninsula Blister Test," The Journal of Adhesion, Vol. 82, pp. 825-860, 2006.

Roy, S., Vangadassalam, K., Wang, Y., Park, S. and Liechti, K. M., "Characterization and Modeling of Strain Assisted Diffusion in an Epoxy Adhesive Layer," International Journal of Solids & Structures, Vol. 43, pp. 27-52, 2006.

Mello, A.V. and K.M. Liechti, "The Effect Of Self-Assembled Monolayers On Interfacial Fracture". Journal of Applied Mechanics, Vol. 73, pp. 860-870, 2006.

Park, S. J., Liechti, K. M. and Roy, S. "Simplified Bulk Experiments and Hygrothermal Nonlinear Viscoelasticity," Journal of Time-Dependent Materials, Vol. 8, pp. 303-344, 2004.

Mello, A. W. and Liechti, K. M. "Controlling Mixed-Mode Interfacial Fracture Toughness with Self-Assembled Monolayers," Journal of Applied Mechanics, accepted 2004.

Mello, A. W. and Liechti, K. M., "A Piezoelectric Biaxial Loading Device For Interfacial Fracture Experiments," Experimental Mechanics, Vol. 44, pp. 495-501, 2004.

Wang, M., Liechti, K. M., White, J. M., and Winter, R. M., "Nanoindentation of Polymeric Thin Films with an Interfacial Force Microscope," Journal of the Mechanics and Physics of Solids, Vol. 52(10), pp. 2329-2354, 2004.

Wang, M., Liechti, K. M., Srinivasan, V., White, J. M., Rossky, P. J., and Stone, M. T., "A Hybrid Molecular-Continuum Analysis of IFM Experiments of a Self-Assembled Monolayer," Journal of Applied Mechanics, Vol. 73, 769-777.

Wang, M., Liechti, K. M., Wang, Q., and White, J. M., "Self-Assembled Silane Monolayers: Fabrication with Nanoscale Uniformity," Langmuir, Vol. 21(5), pp. 1848 - 1857, 2005.

Popelar, C. F., and Liechti, K. M., "A Distortion-Modified Free Volume Theory for Nonlinear Viscoelastic Behavior," Journal of Time-Dependent Materials, Vol. 7(2): 89-141, 2003.

Park, S. J. and Liechti, K. M. "Rate-dependent Large Strain Behavior of a Structural Adhesive," Journal of Time-Dependent Materials,Vol. 7(2): 143-164, 2003.

Arzoumanidis, G. A. and Liechti, K. M. "Linear Viscoelastic Property Measurement and its Application to Modified Free Volume Models," Journal of Time-Dependent Materials, Vol. 7, No. 3, pp. 209-215, 2003.

Liechti, K. M. and Marton, B. "Delamination of a Hight-Temperature Sandwich Plate," Experimental Mechanics, Vol. 42, pp. 206-213, 2002.

Liechti, K. M., Arzoumanidis, A. G., and Park, S-J., "Fatigue Fracture of Fully Saturated Bonded Joints," Journal of Adhesion, Vol. 78, pp. 383-411, 2002.

Swadner, J. G. and Liechti, K. M. , "Shear Induced Toughening in Bonded Joints: Experiments and Analysis," International Journal of Fracture, Vol. 114, pp. 113-132, 2002.

Mohammed, I. and Liechti, K. M., "The Effect of Corner Angles in Bimaterial Structures," International Journal of Solids and Structures, Vol. 38, 4375-4397,2001.

Liechti, K. M. "Fracture Mechanics and Singularities in Bonded Systems," Accepted as a Chapter in Comprehensive Adhesion Science 2001

Wu, J-D, and Liechti, K. M., "Mixed-Mode, Time Dependent Rubber/Metal Debonding," Journal of the Mechanics and Physics of Solids, Vol. 49, pp. 1039-1072 2001.

Wu, J-D. and Liechti, K. M., "Multiaxial And Time-Dependent Behavior Of A Filled Rubber," Journal of Time-Dependent Materials, Vol 4, pp. 293-331, 2000.

Liechti, K. M., Shirani, A., Dillingham, R. G., Boerio, F. J. and Weaver, S. M., "Cohesive Zone Models of Polyimide /Aluminum Interphases," Journal of Adhesion, Vol. 73, 259-297, 2000.

Roy, S. Xu, W.Q., Park, S.J. and Liechti, K.M., "Anomalous Diffusion in Polymers: Experiments and Analysis," ASME Journal of Applied Mechanics, Vol 8, No5, pp.295-305, 2000.

Mohammed, I., and Liechti, K. M., "Cohesive Zone Modeling of Crack Nucleation at Bimaterial Corners," Journal of the Mechanics and Physics of Solids, Vol. 48, pp. 735-764, 2000.

Hung, S.-C. and Liechti, K. M., "Nonlinear Multiaxial Behavior and Failure of Fiber Reinforced Composites," American Society for Testing and Materials, STP. 1357, pp. 176-222, 2000.

Swadener, J. G., Liechti, K. M. and A. L. Lozanne, "The Intrinsic Toughness and Adhesion of a Glass Epoxy Interface," Journal of the Mechanics and Physics of Solids, Vol. 47, pp. 223-258, 1999.

Hung, S.-C. and Liechti, K. M., "Finite Element Analysis of the Arcan Specimen for Fiber Reinforced Composites Under Pure Shear and Biaxial Loading," Journal of Composite Materials, Vol. 33, pp.1288-1317,1999.

Shirani, A. and Liechti, K. M., "A Calibrated Fracture Process Zone Model for Thin Film Blistering," International Journal of Fracture, Vol. 93, pp. 281-314, 1998.

Liechti, K. M., Schnapp, S. T., and Swadener, J. G., "Contact Angle and Contact Mechanics of a Glass/Epoxy Interface," International Journal of Fracture, Vol. 86, 361-374, 1998.

Swadener, J. G. and Liechti, K. M., "Asymmetric Shielding Mechanisms in the Mixed-Mode Fracture of a Glass/Epoxy Interface," ASME Journal of Applied Mechanics, 65, .25-29, 1998.

Hung, S.C. and Liechti, K. M., "An Evaluation of the Arcan Specimen for Determining the Shear Moduli of Fiber Reinforced Composites," Experimental Mechanics, Vol. 37, 460-468, 1997.

Popelar, C. F., and Liechti, K. M., "Multiaxial Nonlinear Viscoelastic Characterization and Modeling of a Structural Adhesive," ASME Journal of Engineering Materials and Technology, Vol. 119, 205-210, 1997.

Liang, Y.-M., and Liechti, K. M., "On the Large Deformation and Localization Behavior of an Epoxy Resin Under Multiaxial Stress States," International Journal of Solids and Structures, Vol. 33, pp.1479-1500, 1996.

Kyriakides, S., Arseculeratne, R., Perry, E. J., and Liechti, K. M., "On the Compressive Failure of Fiber Reinforced Composites," Journal of Solids and Structures, Vol. 32, 689-738, 1995.

Liang, Y.-M., and Liechti, K. M., "Toughening Mechanisms in Mixed-Mode Interfacial Fracture," International Journal of Solids and Structures,Vol. 32, 957-978, 1995.

Liechti, K. M., and A. Shirani, "Large Scale Yielding in Blister Specimens," International Journal of Fracture, Vol. 67, 21-36, 1994.

Liechti, K. M., "On the Use of Classical Interferometry Techniques in Fracture Mechanics," Chapter 4, 95-124, in Experimental Techniques in Fracture, III, Ed. J. S. Epstein, VCH Publishers, New York, 1993.

Liechti, K. M. and Chai, Y.-S. "Asymmetric Shielding in Interfacial Fracture Under In-Plane Shear," Journal of Applied Mechanics, Vol. 59, 295-304, 1992.

Liechti, K. M. and Liang, Y.-M., "The Interfacial Fracture Characteristics of Bimaterial and Sandwich Blister Specimens," International Journal of Fracture, Vol. 55, 95-114, 1992.

Liechti, K. M., Chai, Y.-S., and Liang, Y.-M., "Three-Dimensional Effects in Interfacial Crack Propagation," Experimental Mechanics, Vol. 32, 218-224, 1992.

Liechti, K. M. and Adamjee, W., "Mixed-Mode Cathodic Delamination of Rubber from Steel," J. Adhesion, Vol. 40, 27-45, 1992.

Liechti, K. M. and Chai, Y-S. , "Biaxial Loading Experiments for Determining Interfacial Fracture Toughness," Journal of Applied Mechanics, Vol. 58, pp.  680-687, 1991.

Liechti, K. M. and  Hayashi, T., "On the Uniformity of Stresses in Some Adhesive Deformation Specimens," Journal of Adhesion, Vol. 29, pp. 167-191, 1989.

Liechti, K. M. and Freda, T. "On the Use of Laminated Beams for the Determination of Pure and Mixed-Mode Fracture Properties of Structural Adhesives," Journal of Adhesion, Vol. 28, pp. 145-169, 1989.

Liechti, K. M., Becker, E. G., Lin, C., and Miller, T., "A Fracture Analysis of Cathodic Delamination in Rubber to Metal Bonds," International Journal of Fracture, Vol. 39, pp.  217-234, 1989.

Liechti, K. M. and Hanson, E. C., "Nonlinear Effects in Mixed-Mode Interfacial Delaminations," International Journal of Fracture, Vol. 36, pp. 199-217, 1988.

Liechti, K. M., "Residual Stresses in Plastically Encapsulated Microelectronic Devices," Experimental Mechanics, Vol. 25, pp. 226-231, 1985.

Liechti, K. M. and W. G. Knauss, W. G., "Crack Propagation at Material Interfaces: II. Experiments in Mode Interaction," Experimental Mechanics, Vol. 22, pp. 383-391, 1982.

Liechti, K. M. and W. G. Knauss, W. G., "Crack Propagation at Material Interfaces: I. Experimental Technique to Determine Crack Profiles," Experimental Mechanics, Vol. 22, pp 262-269, 1982.