scholarly journals Mechanical Properties of Finger-Jointed Wood from Composite Utility Poles Made of Small Diameter Timber

2016 ◽  
Vol 67 (1) ◽  
pp. 73-78
Author(s):  
Cheng Piao ◽  
Todd Shupe
Keyword(s):  
Mechanical Properties ◽  
Small Diameter ◽  
Utility Poles

Bioengineering silk into blood vessels

2021 ◽  
Author(s):  
Yuen Ting Lam ◽  
Richard P. Tan ◽  
Praveesuda L. Michael ◽  
Kieran Lau ◽  
Nianji Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Inflammatory Responses ◽  
Vascular Grafts ◽  
Small Diameter ◽  
Biological Response ◽  
Endothelial Cell Layer ◽  
Significant Research ◽  
Rising Incidence ◽  
Highly Hydrophobic ◽  
Synthetic Grafts

The rising incidence of cardiovascular disease has increased the demand for small diameter (<6 mm) synthetic vascular grafts for use in bypass surgery. Clinically available synthetic grafts (polyethylene terephthalate and expanded polytetrafluorethylene) are incredibly strong, but also highly hydrophobic and inelastic, leading to high rates of failure when used for small diameter bypass. The poor clinical outcomes of commercial synthetic grafts in this setting have driven significant research in search of new materials that retain favourable mechanical properties but offer improved biocompatibility. Over the last several decades, silk fibroin derived from Bombyx mori silkworms has emerged as a promising biomaterial for use in vascular applications. Progress has been driven by advances in silk manufacturing practices which have allowed unprecedented control over silk strength, architecture, and the ensuing biological response. Silk can now be manufactured to mimic the mechanical properties of native arteries, rapidly recover the native endothelial cell layer lining vessels, and direct positive vascular remodelling through the regulation of local inflammatory responses. This review summarises the advances in silk purification, processing and functionalisation which have allowed the production of robust vascular grafts with promise for future clinical application.

The Structure and the Mechanical Properties of a Newly Fabricated Cellulose-Nanofiber/Polyvinyl-Alcohol Composite

2014 ◽  
Vol 1621 ◽  
pp. 149-154
Author(s):  
Yukako Oishi ◽  
Atsushi Hotta
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Cellulose Nanofibers ◽  
Small Diameter ◽  
Short Fiber ◽  
Cellulose Nanofiber ◽  
Process Conditions ◽  
Aspect Ratios

ABSTRACTCellulose nanofibers (Cel-F) were extracted by a simple and harmless Star Burst (SB) method, which produced aqueous cellulose-nanofiber solution just by running original cellulose beads under a high pressure of water in the synthetic SB chamber. By optimizing the SB process conditions, the cellulose nanofibers with high aspect ratios and the small diameter of ∼23 nm were obtained, which was confirmed by transmission electron microscopy (TEM). From the structural analysis of the Cel-F/PVA composite by the scanning electron microscopy (SEM), it was found that the Cel-F were homogeneously dispersed in the PVA matrix. Considering the high molecular compatibility of the cellulose and PVA due to the hydrogen bonding, a good adhesive interface could be expected for the Cel-F and the PVA matrix. The influences of the morphological change in Cel-F on the mechanical properties of the composites were analysed. The Young’s modulus rapidly increased from 2.2 GPa to 2.9 GPa up to 40 SB treatments (represented by the unit Pass), whereas the Young’s modulus remained virtually constant above 40 Pass. Due to the uniform dispersibility of the Cel-F, the Young’s modulus of the 100 Pass composite at the concentration of 5 wt% increased up to 3.2 GPa. The experimental results corresponded well with the general theory of the composites with dispersed short-fiber fillers, which clearly indicated that the potential of the cellulose nanofibers as reinforcement materials for hydrophilic polymers was sufficiently confirmed.

A Case Study of Gas Leakage and Assessment of Mechanical Properties With Welding Variables in Fillet Weldment of Small Diameter Pipe

2006 ◽  
Author(s):  
Jong-Hyun Baek ◽  
Woo-Sik Kim
Keyword(s):  
Mechanical Properties ◽  
Fatigue Strength ◽  
Natural Gas ◽  
Weld Zone ◽  
Branch Pipe ◽  
Small Diameter ◽  
Welding Process ◽  
Pipe Diameter ◽  
Pipe Material ◽  
Gas Leakage

A branched pipe joint has been employed to execute the pressure control, condition check, purgation, and distribution of the gas in the natural gas facilities. Installation of branch pipes is generally done through the welding work, and as a welding process, the weldolet and the sockolet are used. During the maintenance working of in-service natural gas pipeline, there was gas leakage in sockolet weldment. The causes of incident were investigated with various tests. We found the wrong pipe material, the weld defect and the non-destructive test limitation of fillet weldment as the reasons of gas leakage. As the follow-up measures, it was done to assess the soundness depending upon the configuration of the weld zone, a change in the welding process and a change in the pipe diameter by assessing the mechanical properties of the sockolet weld zone and further to assess comparatively the mechanical performance of the sockolet weld zone and that of the weldolet weld zone. In the sockolet weld, the tensile strength showed no difference and the fatigue strength showed a difference depending upon a change in the welding process. In the case that the leg length of the weld zone was made lengthwise in the direction of the branch pipe, the SMAW welding work compare with the GTAW, the sectional area of the weld zone was more increased, and the pipe diameter was more increased, the fatigue strength was increased.

Evaluating timber quality in larger-diameter standing trees: rethinking the use of acoustic velocity

Holzforschung ◽  
2019 ◽  
Vol 73 (9) ◽  
pp. 797-806 ◽  
Author(s):  
Luka Krajnc ◽  
Niall Farrelly ◽  
Annette M. Harte
Keyword(s):  
Mechanical Properties ◽  
Bending Strength ◽  
Small Diameter ◽  
Longitudinal Direction ◽  
High Ratio ◽  
Acoustic Velocity ◽  
Timber Quality ◽  
Standing Trees ◽  
The Mean ◽  
Acoustic Velocities

AbstractThe use of acoustic velocity for different purposes is becoming widespread in the forestry industry. However, there are conflicting reports on how well this technology reflects the mechanical properties of trees. In this study, the prediction of timber quality using acoustic technology was evaluated on mature standing trees of three softwood species. The velocity in 490 standing trees was measured in several directions (longitudinal, radial and tangential). A sub-sample of trees was felled and the acoustic velocity was measured in 120 logs which were then sawn into structural-sized timber. A total of 1383 boards were tested for bending, as were small clear specimens extracted from the structural-sized boards. The mean tree values of the timber grade-determining properties (elastic modulus, bending strength and density) of both specimen sizes were related to the acoustic velocities and tree slenderness. The correlations between the mean tree mechanical properties and acoustic velocities were relatively low, most likely due to a high ratio of diameter to measurement distance. The transverse directions showed similar correlations with mechanical properties in larger-diameter trees to the longitudinal direction, as did tree slenderness. The results suggest that while the acoustic velocity in the longitudinal direction can reflect the mean tree mechanical properties in small-diameter trees, alternatives are needed to achieve the same in larger-diameter trees.

Fabrication and Preliminary Study of a Prototype Bi-Layered Small Diameter Vascular Prosthesis Composed of Nano-Fiber and Silk Fiber

2013 ◽  
Vol 843 ◽  
pp. 66-69 ◽  
Author(s):  
Hui Jing Zhao ◽  
Guo Li Zhou ◽  
Zhi Qing Yuan
Keyword(s):  
Mechanical Properties ◽  
Blood Vessels ◽  
Outer Layer ◽  
Small Diameter ◽  
Peak Stress ◽  
Silk Fiber ◽  
Content Increase ◽  
Peak Strain ◽  
Tissue Engineering Scaffolds ◽  
Vascular Prostheses

Biomaterials used for vascular prostheses should possess certain strength that can keep the normal blood fluidity, as well as certain flexibility and elasticity that can resist blood pulsation pressure. In order to fabricate small diameter vascular prostheses (SDVP) that possess matchable mechanical properties with natural blood vessels, a bi-layered tubular structure composed of electrospinning blended nanofiber and silk fiber was designed and prepared in this study. The inner layer of the structure, prepared through electrospinning, was composed of Poly (L-lactide-co-ε-caprolactone) (PLCL) and silk fibroin (SF) blended nanofibers. Braided silk tube was used as the outer layer of the structure. Morphological, structural and mechanical properties including peak stress, peak strain, and Youngs modulus of the prototype bi-layered SDVP were characterized initially. Results showed that the diameter range of the blended nanofiber was between 100 and 900 nm, and the fiber diameter increased with the content increase of PLCL. Through blending PLCL together with SF, peak stress and peak strain of the electrospun inner layer were improved, and that of the Youngs modulus decreased. Meanwhile, the outer layer of SDVP was stronger and had higher Youngs modulus. Those mechanical performances of the prototype bi-layered SDVP fabricated in this study are similar to natural blood vessels, which provide a promising biomaterial that could be applied on tubular tissue engineering scaffolds.

Biomimetic Hemocompatible Nanofibrous Scaffolds as Potential Small-Diameter Blood Vessels by Bilayering Electrospun Technique

2011 ◽  
Vol 306-307 ◽  
pp. 1627-1630 ◽  
Author(s):  
He Yun Wang ◽  
Ya Kai Feng ◽  
Hai Yang Zhao ◽  
Ruo Fang Xiao ◽  
Jin Tang Guo
Keyword(s):  
Mechanical Properties ◽  
Blood Vessel ◽  
Breaking Strength ◽  
Small Diameter ◽  
Matrix Structure ◽  
Complex Matrix ◽  
Elongation At Break ◽  
Artificial Blood ◽  
Nanofibrous Scaffolds ◽  
Morphology And Mechanical Properties

In this paper, we prepared a scaffold composed of a polyurethane (PU) fibrous outside-layer and a gelatin-heparin fibrous inner-layer with mimicking morphology and mechanical properties of a native blood vessel by sequential bilayering electrospinning technology on a rotating mandrel-type collector. The scaffolds achieved the appropriate breaking strength (3.7 ± 0.13 MPa) and elongation at break (110 ± 8%). When the scaffolds were immersed in water for 1 h, the breaking strength decreased slightly to 2.2 ± 0.3 MPa, but the elongation at break increased up to 145 ± 21%. Heparin was released from the scaffolds at substantially uniform rate until the 9th day. The scaffolds were expected to mimic the complex matrix structure of native arteries, and had good hemocompatibility as an artificial blood vessel owing to the heparin release.

Theory and Experiments for Mechanically-Induced Remodeling of Tissue Engineered Blood Vessels

2008 ◽  
Vol 57 ◽  
pp. 226-234 ◽  
Author(s):  
Rudolph L. Gleason ◽  
William Wan
Keyword(s):  
Mechanical Properties ◽  
Blood Vessels ◽  
Laser Scanning ◽  
Biomechanical Testing ◽  
Small Diameter ◽  
Mechanical Stimuli ◽  
Two Photon ◽  
Constrained Mixture ◽  
Tissue Engineered Blood Vessels ◽  
Luminal Flow

There is a great unmet clinical need to develop small diameter tissue engineered blood vessels (TEBV) with low thrombogenicity and immune response and suitable mechanical properties. In this paper we describe experimental and computational frameworks to characterize the use of mechanical stimuli to improve the mechanical properties of TEBVs. We model the TEBV as a constrained mixture and track the production, degradation, mechanical state, and organization of each structural constituent. Specifically, we assume that individual load bearing constituents can co-exist within each neighborhood and, although they are constrained to deform together, each constituent within this neighborhood may have different natural (i.e., stress-free) configurations. Motivated by this theoretical framework, we have designed a bioreactor and biomechanical testing device for TEBVs. This device is designed to provide precise and independent control of mean and cyclic luminal flow rate, transmural pressure, and axial load over weeks and months in culture and perform intermittent biaxial biomechanical tests. This device also fits under a two-photon laser scanning microscope for 3-dimenstional imaging of the content and organization of cells and matrix constituents. These data directly support our theoretical model.

Sign in / Sign up

Export Citation Format

Share Document