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- Joffre, Thomas, et al.
(författare)
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Microscopic strain fields at crack tips in porous materials analyzed by a gradient-enhanced elasticity theory
- 2016
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Ingår i: Engineering Fracture Mechanics. - : Elsevier BV. - 0013-7944 .- 1873-7315. ; 168, s. 160-173
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Tidskriftsartikel (refereegranskat)abstract
- The microstructural influence on the strain field at opening mode crack tips in porous materials, and especially its practical implication for understanding macroscopic failure, i.e. on a scale above, is investigated. Theoretical subscale microstrain fields are approximated using a gradient-enhanced elasticity theory and compared to microstrain fields computed in discrete high-resolution finite element microstructural models having varying pore densities but similar macroscopic geometry and boundary conditions as the theoretical gradient-enhanced model. The numerical elastic microstrain and microstress fields are non-singular in strong contrast to the singular macroscopic fields in classical linear elastic fracture theories. Experimentally approximated microstrain fields, estimated with a digital image correlation algorithm on images obtained in X-ray computational tomography fracture tests on a small wood specimen, are used to contrast the.numerical analyses. A key observation is that an internal length parameter, used in the gradient-enhanced model, seems to be linked to the average pore diameter, allowing for direct bridging between scales.
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- Tummala, Gopi Krishna, 1986-, et al.
(författare)
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Hyperelastic Nanocellulose-Reinforced Hydrogel of High Water Content for Ophthalmic Applications
- 2016
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Ingår i: ACS Biomaterials Science & Engineering. - : American Chemical Society (ACS). - 2373-9878. ; 2:11, s. 2072-2079
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Tidskriftsartikel (refereegranskat)abstract
- A nanocellulose-reinforced poly(vinyl alcohol) hydrogel material of exceptionally high water content for ophthalmic applications is presented (>90 wt %), which also features a hitherto unprecedented combination of optical, mechanical, viscoelastic, oxygen permeability, and biocompatibility properties. The hydrogel combines the desired softness with remarkable strain-dependent mechanical strength and thereby demonstrates hyperelastic, rubber-like mechanical properties. The observed unusual mechanical behavior is due to both high water content and the combination of relatively stiff cellulose nanowhiskers entangled in a soft polymer matrix of poly(vinyl alcohol) (PVA), thus mimicking the structural characteristics of the cornea's main constituents, i.e., water and collagen.
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