Jinlong Guo
Ph.D. Candidate
Aerospace Engineering and Engineering Mechanics
The University of Texas at Austin
June 16, 2026 Tuesday 10:00-11:00 am
We present the results of an investigation of crack nucleation and propagation in polydimethylsiloxane (PDMS) elastomers using the classical poker-chip experiment. The first objective of this investigation is to quantitatively characterize the evolution of crack nucleation and growth, not only through the usual macroscopic load–displacement response, but also through synchronized optical images with high spatial resolution and adequate temporal resolution, augmented with X-ray computed tomography scans. The experiments reveal that the first interior crack does not nucleate at the radial center, where the hydrostatic stress is largest, but instead nucleates at some distance away from the center. When the diameter-to-thickness aspect ratio is sufficiently large, failure is dominated by the nucleation of multiple microcracks. In contrast, specimens with smaller aspect ratios tend to nucleate fewer cracks, and failure is dominated by the growth of these cracks.
We then show that a local fracture criterion is not sufficient to explain the off-center crack nucleation. To address this limitation, we propose a new nucleation criterion that combines the hydrostatic stress with a nonlocal measure of the strain energy. The stability and slanted growth of macro cracks are then quantified through calculations of the energy release rate. We further show that subsequent crack nucleation can be explained by the proposed nucleation criterion together with the stable growth of pre-existing cracks. This reveals why specimens with larger diameter-to-thickness ratios tend to nucleate more independent cracks, while the inter-crack distance appears to be independent of the aspect ratio. Finally, the poker-chip experiment is extended to PDMS elastomers with different composition ratios, revealing a transition in the crack nucleation and growth behavior.
Zoom Link: https://utexas.zoom.us/j/2079375792pwd=jibj2pmpr0eIBsQFp9dn81WiSQfFxH.1&omn=87802599346 – Password: fracture
Contact: K. Ravi-Chandar (ravi@utexas.edu)