Ehlersfoss1971

Good agreement is demonstrated between the experimental data and results of simulation. The influence of volume fraction of nanoparticles, concentration of cross-links, and topology of a polymer network on material parameters is analyzed numerically.Human tooth enamel, the most mineralized tissue in body, contains less than 2 wt% protein. Consequently, the importance of the protein to enamel mechanical response has always been overlooked. In this study, the role of minor protein in providing enamel microstructure and mechanical performance, especially tribological properties, were studied using deproteinization treatment and nano-indentation/scratch technique. Via the change from the original to the deproteinated conditions, a nanostructure degeneration from the assembly of hydroxyapatite (HA) crystals into nano-fibers to crystal aggregation has been found between the high-wear-resistance and low-wear-resistance on the enamel surface. Correspondingly, an energy dissipation to cause a unit volume of wear on enamel surface decreases by 50%, and wear volume increases by 80%. With the presence of protein, the occurrence of enamel wear requires to break the interfacial protein bonding between the HA crystals in nano-fibers and the break dissipates considerable energy, which benefits the enamel to resist wear. Thus, the protein in enamel, although of a very low content, is essential to resisting wear by mediating the assembly of rigid HA crystals via interfacial protein bonding. Replicating functions of the protein component will be critical to the successful development of bio-inspired materials that are designed for wear-resistance.Bamboo achieves its mechanical efficiency in bending and compression, meaning mechanical performance per unit mass, due to its hierarchical structure. As an orthotropic tube with a higher strength and stiffness parallel to the tube axis and with a density and property gradient across the tube wall, in which fiber bundles are embedded in a porous matrix, the bamboo culm is both stiffer and stronger in bending and less prone to ovalization and catastrophic failure than an orthotropic tube without property gradients would be. Few engineered materials exist that emulate bamboo's mechanical efficiency. The results of the study presented here demonstrate that freeze casting (ice templating) is a manufacturing process with which bamboo-inspired tubular scaffolds with property gradients across the tube wall can be custom-made. A highly aligned, honeycomb-like porosity is generated by ice crystal growth opposite to the direction of heat flow. Using a core-shell mold, the microstructure of the tube wall material, such as the pore size, geometry, and alignment, is defined by the mold materials' properties and applied cooling conditions. These also allow to custom-design the desired property gradient across the section. CC-90011 Further customization of the tube gradient structure and properties is possible through the deposition of additional layers on the freeze-cast scaffolds. Characterizing the pore structures of the tubes using X-ray microtomography, pore morphology and property gradients can be analyzed and correlated to both the processing conditions and the resulting mechanical properties determined in three-point bending, longitudinal and radial compression. The resulting fundamental structure-property-processing correlations support the custom design of tubular scaffolds that are ideally suited for applications that range from conduits for peripheral nerve repair to ureteral stents.Pulmonary disease is known to cause remodeling of tissue structure, resulting in altered viscoelastic properties; yet the foundation for understanding this phenomenon is still nascent and will enable scientific insights regarding lung functionality. In order to characterize the viscoelastic response of pulmonary airways, uniaxial tensile experiments are conducted on porcine extra- and intra-parenchymal bronchial regions, measuring both axially and circumferentially oriented tissue. Anisotropic and heterogeneous effects on preconditioning and hysteresis are substantial, linking to energy dissipation expectancies. Stress relaxation is rheologically modeled using several classical configurations of discrete spring and dashpot elements; among them, Standard Linear Solid (SLS) and Maxwell-Weichart exhibit better fit performance. Enhanced fractional order derivative SLS (FSLS) model is also evaluated through use of a hybrid spring-pot of order α. FSLS outperforms the conventional models, demonstrating superior representation of the stress-relaxation curve's initial value and non-linear asymptotic decent. FSLS parameters exhibit notable orientation- and region-specific values, trending with observed tissue structural constituents, such as glycosaminoglycan and collagen. To the best of our knowledge, this work is the first to characterize proximal and distal bronchial energy efficiency and contextualize tissue biochemical composition in view of experimental measures and viscoelastic trends. Results provide a foundation for future investigations, particularly for understanding the role of viscoelasticity in diseased states.Understanding the viscoelastic properties of biological tissues is important because they can reveal tissue structure. This study analyzes the viscoelastic properties of soft biological tissues using a fractional dynamics model. We conducted a dynamic viscoelastic test on several porcine samples, i.e., liver, breast, and skeletal muscle tissues, using a plate-plate rheometer. We found that some soft biological tissues have non-minimum phase properties, i.e., the relationship between compliance and phase delay is not uniquely related to the non-integer derivative order in the fractional dynamics model. The experimental results show that the actual phase delay is larger than that estimated from compliance. We propose an empirical model to represent these non-minimum phase properties; a fractional Maxwell model with the fractional Hilbert transform term is proposed. The model and experimental results were highly correlated in terms of compliance and phase diagrams, and complex mechanical impedance. We also show that the amount of additional phase delay, defined as the increase in actual phase delay compared to that estimated from compliance, differs with tissue type.