About

John Lambros is the Willett Professor in Engineering at the College of Engineering, University of Illinois Urbana-Champaign. His research interests encompass fatigue and failure of additively manufactured metals and composites, failure of Li-ion battery electrodes, quasi-static and dynamic fracture of graded materials and composites, and the dynamic response of nanolayered metals. He also investigates micro/meso mechanics of ductile metals, thermomechanical fatigue, static and dynamic fracture mechanics, and jamming of granular media. His work extends to 3D X-ray tomography, digital volume correlation, and the study of wave propagation and fracture in multiphase systems. Lambros holds a Ph.D. in Aeronautics from the California Institute of Technology, earned in 1994, along with a master's degree from Caltech and a bachelor's degree in Aeronautical Engineering from Imperial College of Science and Technology, University of London. His academic career includes positions as a Professor and Associate Head for Graduate Studies at the University of Illinois Urbana-Champaign, as well as visiting professorships at the University of Liverpool. His contributions to aerospace materials and mechanics are documented through chapters in encyclopedias and numerous articles in peer-reviewed journals, focusing on the response of materials under various loading conditions, fracture mechanics, and advanced manufacturing processes.

Research topics

• Composite material
• Materials science
• Metallurgy

Selected publications

• Grain Boundary Fracture of a Magnesium Aluminate Spinel Bi‐Crystal: Microscale Experiments With Varying Mode Mixity

  Journal of the American Ceramic Society · 2026-03-26

  articleOpen accessSenior authorCorresponding

  ABSTRACT In this work, failure of a magnesium aluminate spinel (MgAl 2 O 4 ) is investigated at the microscale by concurrent in situ imaging and loading within a transmission electron microscope. The goal of the effort is to quantitively measure the grain boundary fracture toughness of a spinel bi‐crystal and study the toughness property disparity between the grain boundary and lattice (measured in an earlier effort). Additionally, the mode mixity dependence of the grain boundary fracture properties is measured as the applied loading configuration is varied. By placing a notch aligned with the grain boundary at the top or bottom edge of a bi‐crystal beam sample, bending experiments can generate grain boundary failure with different mode mixites. Critical energy release rates and mode mixity indicators for each sample were extracted through three‐dimensional finite element analysis (FEA), validated by comparison of particle tracking measurements with the FEA results. For opening‐dominated fracture, the grain boundary exhibited a lower fracture energy when compared to the single crystal lattice. Alternatively, shear‐dominated modes exhibit much larger toughness.

  PublisherDOI

• The behaviour of geometrically-reinforced thin plates under thermoacoustic loading: A comparison of additive and subtractive manufacturing

  Journal of Vibration and Control · 2026-02-20

  articleOpen access1st author

  Additive manufacturing (AM) is gaining in popularity as an approach to producing metallic components of complex geometry relatively cheaply and rapidly from digital representations. However, concerns about the impact of residual stresses induced by additive manufacturing on the distortion of parts has limited its application in some fields. Residual stresses in parts that lack rotational symmetry and, or have cross-sections with large aspect ratios could cause significant changes in the structural and dynamic performance of the parts due to changes in their shape. In this study, geometrically-reinforced thin plates of a nickel-chromium alloy have been manufactured using classical, subtractive machining processes, and additively using laser-powder bed fusion (PBF-LB). Their final shapes were measured using stereoscopic digital image correlation. Their thermoacoustic performance was investigated by subjecting them to random broadband excitation between 0 and 2000 Hz while applying a series of spatial distributions of heat so that the plates increased from room temperature to an equilibrium temperature of about 800°C and then were allowed to cool when the heating was switched off. Time-frequency spectrograms were measured during the heating and cooling over a greater frequency range (0 to 2000 Hz) than achieved previously. Mode shifting and mode switching, or jumping, was observed; however, the residual strains induced by the manufacturing processes dominated the thermoacoustic behaviour, with almost no effect from the method of manufacturing.

  PublisherDOI

• Identification Uncertainty in Inverse Material Model Parameter Determination: A Sensitivity‐Based Decision Process for Load Path Selection

  Strain · 2025-05-29 · 2 citations

  articleOpen accessSenior authorCorresponding

  ABSTRACT This research proposes a sensitivity‐based framework for selecting the optimal prescribed loading path for a biaxial cruciform specimen. Optimality here is determined by the direction and magnitude of the prescribed displacement that minimizes the influence of random noise on the material model parameter identification. Using simulated experimental data based on finite element simulation, in this work, we identify the material model parameters of a Ludwik hardening model and plane stress implementation of the Hill‐48 yield criterion using finite element model updating (FEMU). Our analysis reveals that the identification (or estimator) uncertainty of model parameters depends on the displacement boundary conditions (i.e., loading sequence) and the ground‐truth value of the individual parameters. Optimal experimental design (OED) criteria based on the Fisher information matrix were investigated to mitigate indecision in the choice of optimal load path when the identification uncertainty of different material model parameters optimized at different load paths. The determinant of the Fisher information matrix was chosen here as the more useful metric due to its ability to capture uncertainty of the most influential material model parameters. The proposed framework demonstrates potential for real‐time automated load step selection using scalar criteria derived prior to mechanical loading. The framework can be generalized to other geometries, boundary conditions and material models, allowing this procedure to be utilized for different experimental configurations and materials.

  PublisherOA PDFDOI

• A Comparative Study of the Modal Response of Additively and Subtractively Manufactured Thin Plates After Thermal Loading

  Experimental Mechanics · 2025-01-23 · 1 citations

  articleOpen access

  Background: Additively-manufactured parts contain residual stresses induced by manufacturing. These residual stresses can be relaxed or redistributed by thermal loading. The presence of internal stress influences the dynamic response of parts, and this is of particular interest in thin plates subject to thermoacoustic loading in hypersonic vehicles and fusion reactors. Objective: To measure the changes in shape and modal frequencies caused by thermal loading of geometrically-reinforced thin plates that were additively manufactured in Inconel 625. Methods: Plates were additively-manufactured in landscape and portrait orientations using laser powder bed fusion. The plates were heated to a nominal temperature of 820 °C, which was expected to alleviate the residual stress from the build process. Pre- and post-heating, their modal frequencies were found experimentally and pulsed-laser stereo (3D) digital image correlation was used to evaluate their modal shapes. The resultant modal frequencies and shapes were compared with those from a subtractively-manufactured plate. Results: It was found that the heat cycle changed the shape of the plates relative to their as-manufactured state in addition to changing their natural frequencies and modal shapes. Conclusions: The change in shape induced by heating caused shifts in the natural frequencies and changes in the corresponding modal shapes. The results show quantitatively for the first time the important role that residual stresses can play in the dynamic response of geometrically-reinforced thin plates manufactured by additive and subtractive processes. Supplementary Information: The online version contains supplementary material available at 10.1007/s11340-024-01130-5.

  PublisherOA PDFDOI

• Microscale strain field predictions from grain microstructure of polycrystalline metals using fully convolutional networks

  International Journal of Solids and Structures · 2025-12-04 · 1 citations

  articleOpen access
  PublisherDOI

• Opening-Dominated Fracture Characterization of Single Crystal Spinel in the Transmission Electron Microscope

  Experimental Mechanics · 2025-06-11

  articleOpen accessSenior author

  Abstract Background Characterizing deformation and failure mechanisms through small-scale testing has helped in the fundamental understanding of material response, and direct loading in a transmission electron microscope (TEM) has played a large role in this effort. However, crystalline materials exhibit incoherent scattering within the TEM and the resulting intensity variations inhibit direct optical metrology. Objective In this work, we seek to both validate an in situ optical full-field metrology method in the TEM for use with crystalline materials, and measure fracture properties of a MgAl 2 O 4 spinel single crystal at the microscale. Methods Microscale single edge notch bend beams were machined from a spinel single crystal and loaded in the TEM. In situ imaging of a nanoscale speckle pattern allowed use of particle tracking (PT) to extract full-field measurements of the displacement field. A numerical analysis methodology was then used to obtain mixed mode stress intensity factor values. Results A discrepancy between PT and far-field actuator measurements of applied displacement was found (about a maximum of 35% difference), indicating the advantage of using near-field optical measurements in the TEM. For such small-scale testing it is also generally unavoidable to introduce asymmetry in loading. However, the PT results allowed measurement of both K I and K II , which were found to be at the time of crack initiation K IC = 1.51± 0.03 MPa∙m 0.5 , K IIC = 0.04± 0.002 MPa∙m 0.5 , respectively. Conclusions The application of PT enables full-field deformation measurements on crystalline materials deformed in the TEM. The effectiveness of the inverse property extraction was demonstrated by good agreement between the full-field PT measurements and FEM results. The MgAl 2 O 4 spinel toughness values extracted also agreed well with previous literature results.

  PublisherOA PDFDOI

• In situ measurements and simulation of residual stresses and deformations in additively manufactured thin plates

  The International Journal of Advanced Manufacturing Technology · 2024-04-18 · 3 citations

  articleSenior author
  PublisherDOI

• Quantifying Residual Stresses Generated by Laser-Powder Bed Fusion of Metallic Samples

  Conference proceedings of the Society for Experimental Mechanics · 2024-01-01

  book-chapterSenior author
  PublisherDOI

• Residual Stress Induced in Thin Plates During Additive Manufacturing

  Conference proceedings of the Society for Experimental Mechanics · 2024-01-01 · 1 citations

  book-chapter
  PublisherDOI

• Creep Characterization of Amorphous SiO2 in the Transmission Electron Microscope Using Digital Image Correlation and Finite Element Analysis

  Experimental Mechanics · 2023-02-09 · 6 citations

  articleSenior author
  PublisherDOI

Recent grants

• GOALI: Understanding Light-weight Transparent Ceramic Mechanical Response: From Single Grain Boundary to Bulk Material

  NSF · $477k · 2018–2022

• CMMI-EPSRC: Thermoacoustic Response of Additively Manufactured Metals: A Multi-Scale Study from Grain to Component Scales

  NSF · $748k · 2020–2025

• Rate Effects on the Material and Interfacial Failure of Thin Films From Static to Dynamic Loading

  NSF · $280k · 2006–2010

• US-Turkey Cooperative Research: Three-Dimensional Effects in the Fracture of Functionally Graded Materials

  NSF · $34k · 2003–2008

Frequent coauthors

• Hüseyin Şehitoğlu

  26 shared

• Philippe H. Geubelle

  University of Illinois Urbana-Champaign

  18 shared

• Jay Carroll

  18 shared

• Wael Abuzaid

  American University of Sharjah

  17 shared

• Ares J. Rosakis

  California Institute of Technology

  16 shared

• Ioannis Chasiotis

  14 shared

• E. A. Patterson

  University of Liverpool

  10 shared

• I.M. Robertson

  University of Wisconsin–Madison

  10 shared

Labs

• Combustion, Flow, and Plasma Interaction LaboratoryPI

Education

• Ph.D., Aerospace Engineering

  University of Illinois Urbana-Champaign

Awards & honors

• Alumni Awards and Endowments
• Alumni Loyalty Award
• Distinguished Alumnus Award
• Outstanding Recent Alumni Award