Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

Small but strong: A review of the mechanical properties of carbon nanotube–polymer composites

There have been a number of review papers on layered silicate and carbon nanotube reinforced polymer nanocomposites, in which the fillers have high aspect ratios. Particulate–polymer nanocomposites containing fillers with small aspect ratios are also an important class of polymer composites. However, they have been apparently overlooked. Thus, in this paper, detailed discussions on the effects of particle size, particle/matrix interface adhesion and particle loading on the stiffness, strength and toughness of such particulate–polymer composites are reviewed. To develop high performance particulate composites, it is necessary to have some basic understanding of the stiffening, strengthening and toughening mechanisms of these composites. A critical evaluation of published experimental results in comparison with theoretical models is given.

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Effects of particle size, particle/matrix interface adhesion and particle loading on mechanical properties of particulate–polymer composites

Recently, there has been a rapid growth in research and innovation in the natural fibre composite (NFC) area. Interest is warranted due to the advantages of these materials compared to others, such as synthetic fibre composites, including low environmental impact and low cost and support their potential across a wide range of applications. Much effort has gone into increasing their mechanical performance to extend the capabilities and applications of this group of materials. This review aims to provide an overview of the factors that affect the mechanical performance of NFCs and details achievements made with them.

A review of recent developments in natural fibre composites and their mechanical performance

This review is designed to be a comprehensive source for polymer nanocomposite research, including fundamental structure/property relationships, manufacturing techniques, and applications of polymer nanocomposite materials. In addition to presenting the scientific framework for the advances in polymer nanocomposite research, this review focuses on the scientific principles and mechanisms in relation to the methods of processing and manufacturing with a discussion on commercial applications and health/safety concerns (a critical issue for production and scale-up). Hence, this review offers a comprehensive discussion on technology, modeling, characterization, processing, manufacturing, applications, and health/safety concerns for polymer nanocomposites.

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Review article: Polymer-matrix Nanocomposites, Processing, Manufacturing, and Application: An Overview

In recent years, there has been an increasing interest in seeking for potential civil engineering applications of recycled mixed plastic wastes to relieve the pressure on landfills. This paper presents the recent developments on new generation of composites made from mixed recycled plastics and glass fibre. Glass fibres are one of the most cost-effective reinforcements which can be compounded with recycled thermoplastics to obtain products with improved mechanical property. Some of the first uses for such composites are for the replacement for traditional wooden items like park benches and picnic tables. While these composites are appropriate for such small-scale products, using them in structural applications would consume much greater volume of waste plastics. With its inherent resistance to rot and insect attack, these composites can in fact be used as a replacement for chemically treated timber in various large scale outdoor applications such as railroad crossties and bridges. However, the behaviour of such composites under different environmental conditions such as elevated temperature and ultraviolet rays are crucial. This paper provides an overview of the on-going efforts to address the critical issues for the effective usage of recycled mixed plastics composites in civil engineering and construction.

Glass fibre and recycled mixed plastic wastes: recent developments and applications

Evaluation of the thoracic injury due to blunt impacts during the contact and collision sports activity is very
crucial for the development and validation of the chest protectors for the athletes and safety balls of the sports
such as cricket, baseball, lacrosse and the golf. In order to evaluate the thoracic injury due to solid sports ball
impacts, a series of nonlinear transient dynamic, finite element simulations were carried out by impacting the
FE model surrogate of the thorax 'MTHOTA' (Mechanical THOrax for Trauma Assessment) with a baseball (both soft-core and synthetic) and a cricket ball at impact speed of 10–45 m/s, with an increment of 5 m/s. Only for the impact speed for which measured VCmax was 1 m/s, further simulations were carried out by introducing the ball spin (1000 – 8000 rpm, with an increment of 1000 rpm). Soft-core baseball, synthetic baseball and cricket ball impacts have caused VCmax = 1.0 m/s (25% probability for AIS3+ injuries) at impact speeds of 30.7 m/s, 27.9 m/s and 23.2 m/s respectively. For the normal impacts, spin (about impact direction and two directions perpendicular to the impact direction) of the ball has got no impact on the blunt thoracic trauma. At usual pitching speeds, soft-core baseball didn't offer any safety and performance point of view, it was found to be as bad as synthetic baseball.

Evaluation of the blunt thoracic trauma caused by solid sports ball impacts

Acoustic Emission (AE) evaluation is one of the fast growing non-destructive techniques, owing to its ability to reveal in advance of any impending failure of a building structure This capability makes the so called passive ultrasonic technique a very good tool in structural health monitoring; especially for composite structures In metallic structures, AE technique is currently well established and able to provide accurate and consistent result However, in composites, the challenge for a reliable AE results is huge due to the orthotropic behaviour of the materials The present study investigates the energy attenuation of AE signals in thin composite plate and utilized the attenuation pattern into non-velocity based source location detection Standard Hsu-Nielsen source location testing was applied on a glass fibre epoxy resin laminate and a single channel AE system was used to acquire AE signals with the support from AEWin software for signal analysis A linear source location algorithm utilizing AE signals energy attenuation patterns was developed and tested for the composite specimen The results revealed that the source location algorithm provides reasonably accurate results of source location for glass fibre epoxy resin laminate

Non-velocity Based Analysis of Passive Ultrasonic Signal for Source Location Detection in Composite Plates: A Pilot Study

Advanced fibre composites which were primarily developed for defense and aerospace industries have made inroads into fast growing and high volume civil infrastructure industry nearly a decade ago There are traditional para-aramid synthetic fibres such as Kevlar which are significantly expensive for the use of civil infrastructure construction The recent development of less expensive, high modulus synthetic fibre has opened a new path for the development of cheaper, high performance, impact resistant composites which are affordable for civil infrastructure development This paper details a study of lower cost, high-energy absorbent continuous fiber laminates, and in particular, high modulus polypropylene (HMPP)fibers Innegra™ S is the commercial name used by
Innegrity for its HMPP fiber

Investigation of the impact properties of glass fibre / HMPP fibre hybrid composite materials for civil infrastructure constructions

Polycarbonate - carbon nanofibers, containing various concentrations of filler ranging from 0 % to 10 % wt. have been investigated by electron spin resonance. The as obtained electron spin resonance spectra are complex due to the overlap of several resonances originating from the conducting electrons delocalized over the metallic domains of nanotubes, from the free radicals generated within the polymeric matrix during the processing step, from insulating graphite particles, and from catalyst residues (observed as magnetic impurities). The effect of the filler on the resonance line shape is analyzed in detail. The shape of resonance spectrum demonstrates that the resonance line located near g=2.00 originates from conducting electrons delocalized over the metallic domains of nanotubes. Thos line was accurately fitted by a Lorentzian line shape.

Kin-tak Lau

Papers

Glass fibre and recycled mixed plastic wastes: recent developments and applications

Evaluation of the blunt thoracic trauma caused by solid sports ball impacts

Non-velocity Based Analysis of Passive Ultrasonic Signal for Source Location Detection in Composite Plates: A Pilot Study

Investigation of the impact properties of glass fibre / HMPP fibre hybrid composite materials for civil infrastructure constructions

Polycarbonate-Carbon Nanofibers Composites: An Electron Spin Resonance Study