An air plasma spray process has been used to apply a model tri-layer Yb2SiO5/Al6Si2O13/Si environmental barrier coating system on SiC test coupons. Significant differences in the thermal expansion of the component layers resulted in periodically spaced mud cracks in the Yb2SiO5 and Al6Si2O13 layers. Upon thermal cycling between 1316°C and 110°C in a 90% H2O/10% O2 environment flowing at 4.4 cm/...

Enamel and dentin compose the crowns of human teeth. They are joined at the dentinoenamel junction (DEJ) which is a very strong and well-bonded interface unlikely to fail within healthy teeth despite the formation of multiple cracks within enamel during a lifetime of exposure to masticatory forces. These cracks commonly are arrested when reaching the DEJ. The phenomenon of crack arrest at the D...

We perform traction experiments on viscous liquids highly confined between parallel plates, a geometry known as the probe-tack test in the adhesion community. Direct observation during the experiment coupled to force measurement shows the existence of several mechanisms for releasing the stress. Bubble nucleation and instantaneous growth had been observed in a previous work. Upon increasing fur...

[1] We examine the local nature of the dynamic stress field in the vicinity of the tip of a semi-infinite sub-Rayleigh (slower than the Rayleigh wave speed, cR) mode II crack with a velocity-weakening cohesive zone. We constrain the model using results from dynamic photoelastic experiments, in which shear ruptures were nucleated spontaneously in Homalite-100 plates along a bonded, precut, and i...

Interface cracks are seldom subjected to pure Mode I or pure Mode II conditions. Station~y interface cracks between two distinct, bonded elastic-creep materials subjected to remotely applied mixed mode loading are simulated. The finite element method (FEM) is used to examine crack tip fields and candidate driving force parameters for crack growth. Plane strain conditions are assumed. In most ca...

This paper investigates the directional stability of crack propagation in adhesively bonded joints. First, an analytical model analyzing the energy balance during the crack propagation in double cantilever beam (DCB) specimens is presented, and the directional stability of cracks is predicted. The results are consistent with the analytical predictions made by Fleck, Hutchinson, and Suo [1] usin...

The generation and the subsequent evolution of dynamic failure events in homogeneous layered materials that occur within microseconds after impact were investigated experimentally. Tested configurations include three-layer and two-layer, bonded Homalite specimens featuring different bonding strengths. High-speed photography and dynamic photoelasticity were utilized to study the nature, sequence...

We present a mechanistically faithful and mathematically sound approach to the numerical simulation of secondary thermal cracks propagation in EGS based on the variational approach to fracture [1-4]. While remaining compatible with classical theories, this approach provides a unified framework to crack nucleation, full path identification, including interaction between multiple cracks, branchin...