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.

/pdf/effects-of-particle-size-particle-matrix-interface-adhesion-yv055zq7xi.pdf

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.

/pdf/review-article-polymer-matrix-nanocomposites-processing-t5m2x7jm1h.pdf

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

Interfacial bonding behaviour of embedded SMA wire in smart composites. Micro-scale observation

Phase Transformation and Thermal Stability of Aged Ti-Ni-Hf High Temperature Shape Memory Alloys

Acoustic Emission (AE) is one of the popular non-destructive (NDT) techniques and its applications have increased subsequently for Structural Health Monitoring (SHM). During the past few decades, many successful research works have evidently shown remarkable capability of AE for early damage detection of composite materials. This paper investigated the application of single channel acoustic emission (AE) source location detection method, utilizing time-frequency analysis for thin composite plates. Besides, failure characterization using Modal Acoustic Emission (MAE) also presented. Modal analysis of AE signals or MAE can offers a better theoretical background for acoustic emission analysis; which is necessary to get more qualitative and quantitative result and therefore, increase the reliability of early failure characterization for thin composite plates. For this study, tensile tests were conducted on the glass fiber epoxy resin specimen with small notch; and four channels of acoustic emission system were used to acquire AE signals. The results revealed that in practical, single channel AE source location was difficult to be done. Also, the study has successfully showed that matrix cracks and fiber fracture produced AE signals which dominated by symmetric wave mode.

/pdf/modal-acoustic-emission-investigation-for-progressive-1z1fha2wlz.pdf

Modal Acoustic Emission investigation for progressive failure monitoring in thin composite plates under tensile test

Recently, the development of smart materials and structures (SMS), at the levels of micro and nanoscale, has grown rapidly due to the requirement of an increasing safety margin of all infrastructure, biomedical and engineering (automotive, aerospace and marine) elements The name 'smart' means that a structure (or a material) should be able to respond to environmental changes or external impacts to keep it in a safe condition, without substantially changing its original functionalities Embedding sensor and actuator technology is one of the most popular topics of all SMS disciplines, because these sensors and actuators are very small and do not influence the mechanical, thermal and geometrical properties of the host structures Ideally, these sensors and actuators are also connected to the central system (commonly called the 'brain') to analyze the condition and control the necessary reaction of the structures Recent research on SMS has been mainly focused on embedding tiny sensors and actuators into advanced composite materials The main reason is because advanced composites have been widely adopted for building large life-concerned structures, like airplanes (both Airbus A380 and Boeing 787) A large portion of their structures are made by carbon and glass fiber composites Most of the rotor blades of helicopters are also made of advanced composites in order to reduce their weight and keep sufficient strength to maintain their stiffness However, these structures are subject to many uncertain influences, such as excitation by unpredictable incoming wind with a frequency close to the natural frequency of the structures, for example, blade?vortex interaction As a result, abnormal vibration and noise may be induced that is severely harmful to the structures In this special issue, several types of smart materials and devices that are used for ensuring the safety of structures are introduced It includes: piezoelectric sensors and actuators, nanoconductive particles, shape memory alloys and magneto-rheological elastomers for advanced composite applications The editors would like to express their sincere appreciation and thanks to all the authors for their scientific contribution to this special issue on 'Smart Composite Materials' for Smart Materials and Structures We convey our gratitude to all the reviewers for their time and dedication We applaud IOP Publishing for their support and encouragement of this special issue and the staff for their special attention and timely response

http://iopscience.iop.org/article/10.1088/0964-1726/18/7/070201/pdf

Smart composite materials : selected papers from the international conference on multifunctional materials and structures (MFMS 08) (Hong Kong, 28-31 July 2008)

The production, consumption and waste generation rate of plastic has increased considerably ever since the first industrial scale production of synthetic polymers took place in the 1940s. In Australia, the plastic solid waste comprises 16% by weight of municipal solid waste and only about one-fourth of these plastic wastes are recycled. One of the best options to increase the recycling rate is to convert these plastic wastes into products suitable for housing and construction. However, a critical technical barrier for widespread use of plastic in structural engineering application is the influence of temperature on the material. This paper reports the effect of elevated temperature on the tensile properties of recycled mixed plastic waste. Recycled mixed plastic were prepared using an injection moulding process and tested using coupon specimens following the ISO 527 standard. The temperature was set at 23oC, 30oC, 40oC, 60oC, 80oC and 100oC. It was observed that when the temperature increases from 23oC to 100oC, the tensile strength and modulus reduced from 14.8 MPa and 906.2 MPa to 3.7 MPa and 179.4 MPa, respectively. This result emphasises to use thermal stabiliser and/or thermal coating to prevent the decrement of mechanical properties.

Kin-tak Lau

Papers

Interfacial bonding behaviour of embedded SMA wire in smart composites. Micro-scale observation

Phase Transformation and Thermal Stability of Aged Ti-Ni-Hf High Temperature Shape Memory Alloys

Modal Acoustic Emission investigation for progressive failure monitoring in thin composite plates under tensile test

Smart composite materials : selected papers from the international conference on multifunctional materials and structures (MFMS 08) (Hong Kong, 28-31 July 2008)

Effect of elevated temperature on the tensile properties of recycled mixed plastic waste