Chemo-mechanics: from delamination of adhesive joints to failure of Li ion batteries

Abstract:

Crack growth in materials often arises from a coupled interplay between mechanical loading and chemical degradation. This talk explores two systems where such interactions govern failure: adhesively bonded ship structures in marine environments, and nickel-rich single-crystal cathode particles in lithium-ion batteries. The first part addresses delamination in maritime structures, where a composite superstructure is bonded to a steel hull using a thick (10mm) MMA adhesive. Drawing on results from the QUALIFY project, we examine saltwater-induced delamination, where competing mechanisms—cathodic delamination, free corrosion, and hydrolysis—can each dominate. Experiments identify hydrolysis as the main driver under oxygen- and ion-limited conditions. A transport-reaction model predicts crack growth based on water diffusion along the interface and accumulation of reaction products, leading to constant crack velocity in diffusion-limited regimes. The second part shifts to energy storage materials. In next-generation batteries, layered nickel-rich cathode particles swell during lithiation. Optical microscopy reveals lithium diffusion patterns within single crystals. Coupled chemo-mechanical simulations show that rapid discharge—on the order of 10 minutes—induces internal stresses sufficient to fracture large particles. These case studies illustrate how stress-assisted chemical processes drive failure across scales, and how combining experiments with transport-reaction-fracture models enables prediction of material reliability in chemically active environments.

Bio:

Norman Fleck’s main interests are in Micromechanics: the development of physically based models of deformation and fracture of engineering materials by experiment, theory and numerical analysis. The research is of broad scope and combines scientific insights with practical applications. A guiding philosophy has been to condense practical engineering design problems into fundamental problems in mechanics, then generate constitutive models and implement them within finite element code. Examples include compressive failure of engineering composites by microbuckling, sintering of thermal barrier coatings and the dependence of their toughness and erosion resistance upon microstructural morphology, coupled electro-mechanical switching of ferroelectric devices, fatigue life prediction, the mechanics of metal rolling of thin foil, size effects in plasticity—from hardness testing to cleavage at crack tips—and, more recently, electro-chemo-mechanical phenomena in solid-state lithium-ion batteries. Norman Fleck is Professor of Mechanics of Materials (since 1997) and Director of the Cambridge Centre for Micromechanics (since 1990) at the University of Cambridge. He was Head of the Mechanics, Materials and Design Division from 1996 to 2008. He is a member of several learned societies (FRS, FREng, NAE, Fellow of the European Mechanics Society), serves on advisory committees (Board of IUTAM), editorial boards of leading mechanics journals, and holds an honorary doctorate from Eindhoven University of Technology.