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Subcritical crack growth can occur under a constant applied load below the threshold value for catastrophic failure, also known as static fatigue. Here, we report how a crack grows under a combination of stress-intensity factor (K) and temperature in a model brittle glass using molecular dynamics simulations. The model glass is under dry conditions, thus avoiding the complexity of corrosion chemistry. The crack growth rate is shown to be inconsistent with the commonly used subcritical crack growth model rooted in the transition state theory (TST), in which the applied stress-intensity factor reduces the transition barrier. A new subcritical crack growth model is proposed with a constant barrier and a K-dependent prefactor in TST, representing the size of the region for potential bond breaking. The thermomechanical condition for subcritical crack growth is also mapped in the K-T domain, in between elastic deformation and catastrophic fracture regimes. Finally, we show substantial crack self-healing once the applied load is removed, under the thermodynamic driving force of surface energy reduction. Our findings provide new insights into the mechanochemical coupling during static fatigue and call for experimental investigation of whether the activation energy is K-dependent. 

Abstract This study integrated high‐throughput computational modeling with experimental validation to investigate rare earth (RE) phosphates as potential environmental barrier coatings (EBCs) for SiC‐based ceramic matrix composites (CMCs). Although RE silicates have been widely studied for EBC applications, they are prone to degradation due to water vapor corrosion and silica volatilization at high temperatures. RE phosphates, with their strong P–O bonds, offer a promising alternative with improved resistance to volatilization. Using the AFLOW computational framework, we performed density functional theory calculations to evaluate the thermomechanical properties of single‐component RE phosphates. Specifically, AFLOW Automatic Elasticity Library (AEL) was employed to predict mechanical properties, and AFLOW Automatic GIBBS Library (AGL) and AFLOW Quasiharmonic Approximation (QHA) were used to estimate thermal properties. Our results indicate that although the AGL method performs well in predicting thermal conductivity, it may not be suitable for screening the coefficient of thermal expansion of RE phosphates. Additionally, we explored the concept of configurational disorder in high‐entropy phosphates to enhance their thermal performance. Our experimental validation supported the computational findings, demonstrating that incorporating multiple RE elements into phosphates can significantly improve the performance of EBCs for SiC‐based CMCs. 

Abstract Understanding the physical and chemical response of materials to impulsive deformation is crucial for applications ranging from soft robotic locomotion to space exploration to seismology. However, investigating material properties at extreme strain rates remains challenging due to temporal and spatial resolution limitations. Combining high-strain-rate testing with mechanochemistry encodes the molecular-level deformation within the material itself, thus enabling the direct quantification of the material response. Here, we demonstrate a mechanophore-functionalized block copolymer that self-reports energy dissipation mechanisms, such as bond rupture and acoustic wave dissipation, in response to high-strain-rate impacts. A microprojectile accelerated towards the polymer permanently deforms the material at a shallow depth. At intersonic velocities, the polymer reports significant subsurface energy absorption due to shockwave attenuation, a mechanism traditionally considered negligible compared to plasticity and not well explored in polymers. The acoustic wave velocity of the material is directly recovered from the mechanochemically-activated subsurface volume recorded in the material, which is validated by simulations, theory, and acoustic measurements. This integration of mechanochemistry with microballistic testing enables characterization of high-strain-rate mechanical properties and elucidates important insights applicable to nanomaterials, particle-reinforced composites, and biocompatible polymers.