New Research In
Articles by Topic
- Agricultural Sciences
- Applied Biological Sciences
- Biophysics and Computational Biology
- Cell Biology
- Developmental Biology
- Environmental Sciences
- Immunology and Inflammation
- Medical Sciences
- Plant Biology
- Population Biology
- Psychological and Cognitive Sciences
- Sustainability Science
- Systems Biology
快乐十分任选3技巧:Sideways and stable crack propagation in a silicone elastomer
This article requires a subscription to view the full text. If you have a subscription you may use the login form below to view the article. Access to this article can also be purchased.
Soft materials exhibit fundamentally different fracture characteristics from other materials, and as such represent an open and fascinating research area. Herein, we have discovered a form of fracture in soft elastomers that we call “sideways cracking” in which cracks propagate perpendicular to their “standard” trajectory. These sideways cracks stably arrest, thereby allowing the material ahead of the crack to continue to sustain large loads. As such, understanding this phenomenon may enable the engineering of highly robust and stretchable materials. To explain this behavior, we perform mechanics-based analyses and substantiate a hypothesis that this behavior stems from structural rearrangement of polymer chains during stretching. Overall, this paper provides fundamental mechanical insight into basic phenomena associated with fracture of elastomers.
We have discovered a peculiar form of fracture that occurs in a highly stretchable silicone elastomer (Smooth-On Ecoflex 00–30). Under certain conditions, cracks propagate in a direction perpendicular to the initial precut and in the direction of the applied load. In other words, the crack deviates from the standard trajectory and instead propagates perpendicular to that trajectory. The crack arrests stably, and thus the material ahead of the crack front continues to sustain load, thereby enabling enormous stretchabilities. We call this phenomenon “sideways” and stable cracking. To explain this behavior, we first perform finite-element simulations that demonstrate a propensity for sideways cracking, even in an isotropic material. The simulations also highlight the importance of crack-tip blunting on the formation of sideways cracks. Next, we provide a hypothesis on the origin of sideways cracking that relates to microstructural anisotropy (in a nominally isotropic elastomer). To substantiate this hypothesis, we transversely prestretch samples to various extents before fracture testing, as to determine the influence of microstructural arrangement (chain alignment and strain-induced crystallization) on fracture energy. We also perform microstructural characterization that indicates that significant chain alignment and strain-induced crystallization indeed occur in this material upon stretching. We conclude by characterizing how a number of loading conditions, such as sample geometry and strain rate, affect this phenomenon. Overall, this paper provides fundamental mechanical insight into basic phenomena associated with fracture of elastomers.
- ?1To whom correspondence should be addressed. Email: .
Author contributions: S.L. and M.P. designed research; S.L. performed research; S.L. and M.P. analyzed data; and S.L. and M.P. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1820424116/-/DCSupplemental.
Published under the PNAS license.