Search results for "Composite"

Giant lateral electrostriction in ferroelectric liquid-crystalline elastomers

2001

Mechanisms for converting electrical energy into mechanical energy are essential for the design of nanoscale transducers, sensors, actuators, motors, pumps, artificial muscles, and medical microrobots. Nanometre-scale actuation has to date been mainly achieved by using the (linear) piezoelectric effect in certain classes of crystals (for example, quartz), and 'smart' ceramics such as lead zirconate titanate. But the strains achievable in these materials are small--less than 0.1 per cent--so several alternative materials and approaches have been considered. These include grafted polyglutamates (which have a performance comparable to quartz), silicone elastomers (passive material--the constri…

2015

AbstractWhile understanding the properties of materials under stress is fundamentally important, designing experiments to probe the effects of large tensile stress is difficult. Here tensile stress is created in thin films of potassium (up to 4 atomic layers) by epitaxial growth on a rigid support, graphite. We find that this “simple” metal shows a long-range, periodic “herringbone” reconstruction, observed in 2- and 3- (but not 1- and 4-) layer films by low-temperature scanning tunneling microscopy (STM). Such a pattern has never been observed in a simple metal. Density functional theory (DFT)simulations indicate that the reconstruction consists of self-aligned stripes of enhanced atom den…

One-piece micropumps from liquid crystalline core-shell particles

2012

Responsive polymers are low-cost, light weight and flexible, and thus an attractive class of materials for the integration into micromechanical and lab-on-chip systems. Triggered by external stimuli, liquid crystalline elastomers are able to perform mechanical motion and can be utilized as microactuators. Here we present the fabrication of one-piece micropumps from liquid crystalline core-shell elastomer particles via a microfluidic double-emulsion process, the continuous nature of which enables a low-cost and rapid production. The liquid crystalline elastomer shell contains a liquid core, which is reversibly pumped into and out of the particle by actuation of the liquid crystalline shell i…

Multiple Surface Cracking and Debonding Failure for Thin Thermal Coatings

2019

Abstract A mechanical analysis of thin films of quasi-brittle materials used as thermal coatings for superalloy substrate is proposed. The study considers a bi-material element subjected to uniform tension formed by a thin layer of quasi-brittle material (typically a ceramic) bonded on an elastic substrate. The bounding between the coating film and the substrate is realized by a very thin primer which mechanically modeled as a zero thickness cohesive frictional interface. The analysis is developed by a non-linear finite element simulation in which, in order to consider damage size effects, a non-local isotropic damage model is adopted for the quasi-brittle coating. The results of the analys…

Multiscale microstructural characterization of particulate-reinforced composite with non-destructive X-ray micro- and nanotomography

2018

Abstract Methods based on X-ray tomography are developed to study the relevant statistical quantities describing the microstructural inhomogeneity of particulate reinforced composites. The developed methods are applied in estimating microstructural inhomogeneity parameters of composites containing metallic glass particles in metal matrix, extruded in varying pressure loads. This study indicates that the critical characteristics with regard to the effect of particle clustering are cluster size and shape, local volume fraction of particles in the cluster and the distance between clusters. The results demonstrate that the spatial distribution of reinforcement is very uneven and the amount of p…

Performance and convergence in municipal waste treatment in the European Union.

2019

This paper assesses performance and convergence in the treatment of municipal waste by the members of the European Union-27 (EU-27) during the period 1995-2016. First, a composite indicator of performance -including landfill, incineration, recycling, and composting and digestion as treatment operations- is computed with Data Envelopment Analysis and Multi-Criteria-Decision-Making techniques at country and year levels. Then, convergence is assessed using the techniques proposed by Phillips and Sul (2007, 2009) and, more recently, by Kong et al. (2017). The best performers are Central and Northern European countries such as Denmark, Austria and Germany, whereas the worst are some Eastern Euro…

RADIATION-CLEAVABLE MICROPARTICLE CHAPERONES FOR DURABILITY-CONTROLLED NANOCOMPOSITE BIOPLASTICS

2012

Polysaccharide micro/nanoparticles, incorporating stabilizers (natural antioxidants), prodegrading agents (such as enzymes or metal oxide nanoparticles) or other active ingredients, can be considered ideal chaperones to introduce various and heterogeneous substances into polysaccharide films in virtue of their structural affinity. The possibility of obtaining biodegradable and colloidally stable nanoparticles from xyloglucan has been here investigated. Xyloglucans are a major class of structural polysaccharides found in the primary cell walls of higher plants. They are particularly interesting raw materials for their excellent film forming properties, thermal stability and hydroxyl rich, hi…

CHARACTERIZATION AND PROCESSABILITY NOF POLYESTER BASED NANOCOMPOSITES

2008

PREPARATION AND CHARACTERIZATION OF CLAY NANOCOMPOSITES BASED ON COMPATIBILIZED POLYAMMIDE6/POLYETHYLENE BLENDS

2008

PAUT inspection of complex shaped composite materials through 6 DOFs robotic manipulators

2015

The requirement to increase inspection speeds for the non-destructive testing (NDT) of composite aerospace parts is common to many manufacturers. The prevalence of complex curved surfaces in the industry provides significant motivation for the use of six-axis robots for the deployment of NDT probes in these inspections. The IntACom project, developed by TWI Technology Centre (Wales) and supported by a number of major aerospace partners and the Welsh government, has produced a prototype robotic NDT system. The prototype system is capable of inspecting complex-geometry composite components with great time savings. Two six-axis robotic arms deploy end effectors carrying phased array ultrasonic…