Digital image correlation analysis of laminated bamboo under transverse compression

The use of laminated bamboo in structural applications is increasing, but the failure mechanisms of the material need further investigation. This study investigated the failure of laminated bamboo under compressive loading using digital image correlation (DIC). Notably, the unique speckled appearance of a bamboo transverse section, resulting from the spatial distribution of vascular fibre bundles in the parenchyma matrix, was directly used for DIC; no sample preparation was necessary. A 45 degree shear face originated from the joint between several strips and led to the ultimate failure of the samples. However, when the strain exceeded 30% the analysis broke down due to sections of the specimen shearing of the sample. Our methodology demonstrates the potential of directly imaging laminated bamboo during mechanical testing to reveal complex full-fi eld in-plane strain distribution, and the development and on-set of failure in the material

Quantitative Ultrasound and B-mode Image Texture Features Correlate with Collagen and Myelin Content in Human Ulnar Nerve Fascicles

We investigate the usefulness of quantitative ultrasound (QUS) and B-mode texture features for characterization of ulnar nerve fascicles. Ultrasound data were acquired from cadaveric specimens using a nominal 30 MHz probe. Next, the nerves were extracted to prepare histology sections. 85 fascicles were matched between the B-mode images and the histology sections. For each fascicle image, we selected an intra-fascicular region of interest. We used histology sections to determine features related to the concentration of collagen and myelin, and ultrasound data to calculate backscatter coefficient (-24.89 dB $\pm$ 8.31), attenuation coefficient (0.92 db/cm-MHz $\pm$ 0.04), Nakagami parameter (1.01 $\pm$ 0.18) and entropy (6.92 $\pm$ 0.83), as well as B-mode texture features obtained via the gray level co-occurrence matrix algorithm. Significant Spearman's rank correlations between the combined collagen and myelin concentrations were obtained for the backscatter coefficient (R=-0.68), entropy (R=-0.51), and for several texture features. Our study demonstrates that QUS may potentially provide information on structural components of nerve fascicles

Why do we observe significant differences between measured and ‘back-calculated’ properties of natural fibres?

The drive towards sustainability, even in materials technologies, has fuelled an increasing interest in bio-based composites. Cellulosic fibres, such as flax and jute, are being considered as alternatives to technical synthetic fibres, such as glass, as reinforcements in fibre reinforced polymer composites for a wide range of applications. A critical bottleneck in the advancement of plant fibre composites (PFRPs) is our current inability to predict PFRP properties from data on fibre properties. This is highly desirable in the cost- and time-effective development and design of optimised PFRP materials with reliable behaviour. This study, alongside limited other studies in literature, have found that the experimentally determined (through single fibre tests) fibre properties are significantly different from the predicted (‘back-calculated’ using the popular rule-of-mixtures) fibre properties for plant fibres. In this note, we explore potential sources of the observed discrepancy and identify the more likely origins relating to both measurement and errors in predictions based on the rule-of-mixtures. The explored content in this discussion facilitates the design of a future investigation to (1) identify the sensitivity of the discrepancy between measured and predicted fibre properties to the various potential origins, (2) form a unified hypothesis on the observed phenomenon, and (3) determine whether the rule-of-mixtures model (in specific cases) can be improved and may be able to predict properties precisely.This is the final version of the article. It first appeared from Springer via http://dx.doi.org/10.1007/s10570-016-0926-

The strength of plants: theory and experimental methods to measure the mechanical properties of stems

From the stems of agricultural crops to the structural trunks of trees, studying the mechanical behaviour of plant stems is critical for both commerce and science. Plant scientists are also increasingly relying on mechanical test data for plant phenotyping. Yet there are neither standardized methods nor systematic reviews of current methods for the testing of herbaceous stems. We discuss the architecture of plant stems and highlight important micro- and macrostructural parameters that need to be controlled and accounted for when designing test methodologies, or that need to be understood in order to explain observed mechanical behaviour. Then, we critically evaluate various methods to test structural properties of stems, including flexural bending (two-, three-, and four-point bending) and axial loading (tensile, compressive, and buckling) tests. Recommendations are made on best practices. This review is relevant to fundamental studies exploring plant biomechanics, mechanical phenotyping of plants, and the determinants of mechanical properties in cell walls, as well as to application-focused studies, such as in agro-breeding and forest management projects, aiming to understand deformation processes of stem structures. The methods explored here can also be extended to other elongated, rod-shaped organs (e.g. petioles, midribs, and even roots).This work is part of a project funded by the Leverhulme Trust (Project title: ‘Natural material innovation’). The project forms a collaboration with the Department of Applied Mathematics and Theoretical Physics, Department of Biochemistry, Department of Chemistry, and Department of Plant Sciences at the University of Cambridge

Optimising ply orientation in structural laminated bamboo

Currently, only two forms of laminated bamboo are commercially available as structural materials: unidirectional beams and boards, and cross-laminated boards. As a natural quasi-unidirectional composite, the lamination of bamboo into plies with specific orientations would allow the design and manufacture of a family of multi-axial composite laminates with unique properties. In this study, we test the tensile mechanical properties of single- and two-ply laminated bamboo at various off-axis loading angles and laminate configurations. The data is then compared to micro-mechanical models for predicting modulus and strength of composite laminates. On the basis of our analyses, we believe there is significant scope to extend the current range of laminated bamboo products to include angle-ply laminates. Moreover, we demonstrate that composite laminate theory is applicable to this natural composite and may be used for design of products and structures

Thermal conductivity of engineered bamboo composites

Here we characterise the thermal properties of engineered bamboo panels produced in Canada, China, and Colombia. Specimens are processed from either Moso or Guadua bamboo into multi-layered panels for use as cladding, flooring or walling. We utilise the transient plane source method to measure their thermal properties and confirm a linear relationship between density and thermal conductivity. Furthermore, we predict the thermal conductivity of a three-phase composite material, as these engineered bamboo products can be described, using micromechanical analysis. This provides important insights on density-thermal conductivity relations in bamboo, and for the first time, enables us to determine the fundamental thermal properties of the bamboo cell wall. Moreover, the density-conductivity relations in bamboo and engineered bamboo products are compared to wood and other engineered wood products. We find that bamboo composites present specific characteristics, for example lower conductivities – particularly at high density – than equivalent timber products. These characteristics are potentially of great interest for low-energy building design. This manuscript fills a gap in existing knowledge on the thermal transport properties of engineered bamboo products, which is critical for both material development and building design.DUS and MCDB thank Mr Robert Cornell (University of Cambridge) for training on thermal conductivity measurement. Special thanks go to Prof Greg Smith and Dr Kate Semple at the University of British Columbia (Department of Wood Science), working on processing of structural bamboo products. This research has been funded by the EPSRC (Grant EP/K023403/1), a Leverhulme Trust Programme Grant, and the Newton Trust.This is the final version of the article. It was first available from Springer via http://dx.doi.org/10.1007/s10853-015-9610-

Targeting c-Met Receptor Overcomes TRAIL-Resistance in Brain Tumors

Tumor necrosis factor related apoptosis-inducing ligand (TRAIL) induced apoptosis specifically in tumor cells. However, with approximately half of all known tumor lines being resistant to TRAIL, the identification of TRAIL sensitizers and their mechanism of action become critical to broadly use TRAIL as a therapeutic agent. In this study, we explored whether c-Met protein contributes to TRAIL sensitivity. We found a direct correlation between the c-Met expression level and TRAIL resistance. We show that the knock down c-Met protein, but not inhibition, sensitized brain tumor cells to TRAIL-mediated apoptosis by interrupting the interaction between c-Met and TRAIL cognate death receptor (DR) 5. This interruption greatly induces the formation of death-inducing signaling complex (DISC) and subsequent downstream apoptosis signaling. Using intracranially implanted brain tumor cells and stem cell (SC) lines engineered with different combinations of fluorescent and bioluminescent proteins, we show that SC expressing a potent and secretable TRAIL (S-TRAIL) have a significant anti-tumor effect in mice bearing c-Met knock down of TRAIL-resistant brain tumors. To our best knowledge, this is the first study that demonstrates c-Met contributes to TRAIL sensitivity of brain tumor cells and has implications for developing effective therapies for brain tumor patients

Spider silk inspired damping fibres drawn from a supramolecular hydrogel composite at room temperature - A step closer to sustainable fibre technology

We report the aqueous self-assembly of hierarchical supramolecular polymer-colloidal hydrogels consisting of functionalized polymer-grafted silica nanoparticles, a hydroxyethyl cellulose derivative and cucurbit[8]uril. The resulting material (98 wt% water) can be drawn into uniform (6 μm) ‘supramolecular fibres’ at room temperature. They exhibited better tensile strength and superior stiffness to natural fibres such as viscose, protein-based silks, and human and animal hair, while cyclic loading tests illustrated their remarkable damping capacity (60–70%). These supramolecular hydrogels represent a new class of hybrid supramolecular composites, opening a window into fibre technology through low-energy manufacturing from a broad range of sustainable materials.Leverhulm

Thermal relaxation of laminated bamboo for folded shells

Laminated bamboo is emerging as a novel material in design and construction. As a natural fibre composite, it has unique mechanical properties that allow for innovations that are not possible in other materials. Here, we discuss one new application of those properties: the development of a novel bending technique using high temperature, and we explore its implications for design. We have explored the fundamental properties of laminated bamboo and its thermal relaxation asit passes the glass transition temperatures of its constituent polymers.By mechanically thinning engineered bamboo material, score lines allow precise, controlled and localised heating that promotes limited but essential elasto-plastic behaviour. Concentrated heating above the glass transition temperature induces property evolution and structural morphology changes, which results in thermal relaxation with minimal recovery and full set upon cooling.This original technology is then deployed in the design and construction of a folded plate helical shell composed of thin laminated bamboo sheets.The presented work is supported by a Leverhulme Trust Programme Grant, and EPSRC Grant EP/K023403/1