Vibration absorption performance of membrane-type metamaterial on a thin plate

This work aims to investigate the vibration absorption performance of membrane-type metamaterial on a thin plate. Simulation work was conducted on membrane-type metamaterial using membrane resonators with various configurations of decorated masses. The bandgap property of membrane-type metamaterial with multiple masses was investigated. It was found that a slight adjustment of location for the decorated masses could result in a 45 Hz change of the membrane-type metamaterial bandgap location. Through the simulation work, the vibration transmissibility of a thin plate attached with membrane resonators was studied and it was showed that this membrane-type resonator could effectively suppress the vibration of a thin plate

Prediction of bandgaps in membrane-type metamaterial attached to a thin plate

This work proposes an analytical method to analyse the bandgap location and width of membrane-type metamaterial when it is attached to a thin plate structure. This method enables the bandgap prediction of such a structure by adjusting the tensile stress of the membrane directly. The accuracy of the model is verified by constructing a finite structure model for numerical simulation and comparing the results. It shows that the results given by the analytical model are primarily consistent with the simulation. The effect of membrane tensile stress and attached mass on the bandgap location and width is also investigated. It is found that the width of bandgap can be increased by increasing the membrane tensile stress and using a heavier mass attached to the membrane

Rheological, Surface Tension and Conductivity Insights on the Electrospinnability of Poly(lactic-co-glycolic acid)-hyaluronic Acid Solutions and Their Correlations with the Nanofiber Morphological Characteristics

In this study, solutions were prepared with fixed concentrations of hyaluronic acid (HA) but varied concentrations of poly (lactic-co-glycolic acid) (PLGA) to emphasize the effects of PLGA concentration and HA addition on solution properties and to further evaluate their electrospinning performance. The dependence of specific viscosity on PLGA concentration was studied to determine the concentration regimes and evaluate the critical concentration (Ce) for successful fiber generation. The Ce of PLGA solutions is 12.07% compared to 10.09% for PLGA-HA solutions. Blending with HA results in a lower concentration dependence and better consistency to the theoretical scaling mechanisms due to the additional topological constrains, which thus result in more chain entanglements. Solutions in semi-dilute entangled regimes show the crossover of complex moduli, verifying the stable and reliable entanglement network. Higher concentrations and HA addition both led to lower crossover frequencies and, thus, a longer relaxation time. The effects of a higher PLGA concentration and HA addition on the surface tension were not evident. However, the HA addition significantly improved the solution conductivity up to three times in the pure PLGA solutions due to its polyelectrolyte nature. Defect-free and uniform nanofibers were generated from 35% to 40% of the PLGA-HA solutions, yet fibers with bead-on-string structures were produced from all studied pure PLGA solutions. Such solution characteristics and parametric correlations can provide predictive insights on tailoring the morphological characteristics of nanofibers for specific applications

A conceptional approach of resin-transfer-molding to rosin-sourced epoxy matrix green composites†

In this concept-proof study, a preform-based RTM (Resin Transfer Molding) process is presented that is characterized by first pre-loading the solid curing agent onto the preform, and then injecting the liquid nonreactive resin with an intrinsically low viscosity into the mold to infiltrate and wet the pre-loaded preform. The separation of resin and hardener helped to process inherently high viscosity resins in a convenient way. Rosin-sourced, anhydrite-cured epoxies that would normally be regarded as unsuited to liquid composite molding, were thus processed. Rheological tests revealed that by separating the anhydrite curing agent from a formulated RTM resin system, the remaining epoxy liquid had its flowtime extended. C-scan and glass transition temperature tests showed that the preform pre-loaded with anhydrite was fully infiltrated and wetted by the liquid epoxy, and the two components were diffused and dissolved with each other, and finally, well reacted and cured. Composite laminates made via this approach exhibited roughly comparable quality and mechanical properties with prepreg controls via autoclave or compression molding, respectively. These findings were verified for both carbon and ramie fiber composites

Hybrid composites of silica glass fibre/nano-hydroxyapatite/polylactic acid for medical application

Fibre reinforced composites (FRC) have shown great potential for the application of internal bone fixation due to mechanical properties that are similar to those of human cortical bones. Ternary composites of silica glass fibres, nano-hydroxyapatite (n-HA) and polylactic acid (PLA) were prepared by compression moulding and their mechanical properties were characterized in this study. With the volumetric content of glass fibre remained constantly at 30% and the volume fraction of n-HA increased from 0% to 5%, the flexural strengths of composites decreased from 625.68 MPa to 206.55 MPa, whereas a gradual increment of flexural modulus from 11.01 to 14.08 GPa were observed at the same time. Within a 28-day degradation period, the flexural strengths decreased by 30%, while no obvious trend of modulus variation was found. The flexural properties of all composites prepared in this study were all found to be close to the reported flexural properties. On the other hand, as more n-HA were incorporated, the water absorption percentages increased, whereas negligible mass loss were recorded. SEM images revealed that the impregnation of fibre mats was poor as loose fibres were observed, which shall be solved in future research to further improve the mechanical properties as well as endurance against degradation. © 2017 International Committee on Composite Materials. All rights reserved

L-DOPA coating improved phosphate glass fibre strength and fibre/matrix interface

publishedVersio

Additive-manufactured gyroid scaffolds of magnesium oxide, phosphate glass fiber and polylactic acid composite for bone tissue engineering

Composites of biodegradable phosphate glass fiber and polylactic acid (PGF/PLA) show potential for bone tissue engineering scaffolds, due to their ability to release Ca, P, and Mg during degradation, thus promoting the bone repair. Nevertheless, glass degradation tends to acidify the surrounding aqueous environment, which may adversely affect the viability and bone-forming activities of osteoblasts. In this work, MgO was investigated as a neutralizing agent. Porous network-phase gyroid scaffolds were additive-manufactured using four different materials: PLA, MgO/PLA, PGF/PLA, and (MgO + PGF)/PLA. The addition of PGF enhanced compressive properties of scaffolds, and the resultant scaffolds were comparably strong and stiff with human trabecular bone. While the degradation of PGF/PLA composite induced considerable acidity in degradation media and intensified the degradation of PGF in return, the degradation media of (MgO + PGF)/PLA maintained a neutral pH close to a physiological environment. The experiment results indicated the possible mechanism of MgO as the neutralizing agent: the local acidity was buffered as the MgO reacted with the acidic degradation products thereby inhibiting the degradation of PGF from being intensified in an acidic environment. The (MgO + PGF)/PLA composite scaffold appears to be a candidate for bone tissue engineering

Prediction of bandgaps in membrane-type metamaterial attached to a thin plate

This work proposes an analytical method to analyse the bandgap location and width of membrane-type metamaterial when it is attached to a thin plate structure. This method enables the bandgap prediction of such a structure by adjusting the tensile stress of the membrane directly. The accuracy of the model is verified by constructing a finite structure model for numerical simulation and comparing the results. It shows that the results given by the analytical model are primarily consistent with the simulation. The effect of membrane tensile stress and attached mass on the bandgap location and width is also investigated. It is found that the width of bandgap can be increased by increasing the membrane tensile stress and using a heavier mass attached to the membrane

Vibration absorption performance of membrane-type metamaterial on a thin plate

This work aims to investigate the vibration absorption performance of membrane-type metamaterial on a thin plate. Simulation work was conducted on membrane-type metamaterial using membrane resonators with various configurations of decorated masses. The bandgap property of membrane-type metamaterial with multiple masses was investigated. It was found that a slight adjustment of location for the decorated masses could result in a 45 Hz change of the membrane-type metamaterial bandgap location. Through the simulation work, the vibration transmissibility of a thin plate attached with membrane resonators was studied and it was showed that this membrane-type resonator could effectively suppress the vibration of a thin plate

The Role of GIS in The Management of Primary Health Care Services

The application of Geographic Information Systems with health has been relatively slow to develop in Australia. The aim of this paper is to show the role that a GIS can play in the management of Divisions of General Practice (GP). We are proposing to use GIS to allow data in General Practice to be analysed visually through desktop mapping as a way of developing a Practice profile. Most of the research projects in this area in western countries are at this stage of development. The favourable conditions in Victoria, Australia (due to the amount of complete digital data bases) allow us to be more ambitious. Thus the aim of the project presented through this paper is not only to reach a visual representation of the spatial health data but to explore the potential of GIS in the following issues:· the combination of health data with other data such as the location and characteristics of private services related with health,· spatial and thematic queries,· sophisticated spatial analyses related with the optimal distribution and location of the practitioners,· simulations regarding the actual and future demand, and · optimal routing Two Divisions of General Practice, one in rural Victoria and one in the metropolitan area of Melbourne, are being used in a pilot study. The data and results presented in this paper are related to these settings