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

Generation of 3D representative volume elements for heterogeneous materials: a review

Synthesis and biomedical applications of aerogels: Possibilities and challenges

Silica aerogels are among the lightest weight solid materials and exhibit other unique properties, in particular an outstanding insulation performance. However, these nanostructured highly porous materials show inherent brittleness that makes their processing and handling difficult and constrains their use in common daily applications. One of the most convincing and effective strategies to reinforce the silica aerogel structure is the manufacturing of aerogel composites with embedded fibres, which significantly contributes to widening their applications. This review encompasses a complete survey on scientific achievements related to silica aerogel composites reinforced with all types of fibres (natural, man-made, organic, inorganic and nanofibres), describing their synthesis approaches and properties. The influence of the embedment of different fibres on the final properties of the composites is thoroughly reported, considering their amount in the matrix and/or their specific characteristics, namely morphology, orientation and optical features. The applications linked to the fibre-reinforced silica aerogel composites are briefly addressed as well, evincing developments in typical functions of aerogels, as thermal and/or acoustic insulators and adsorbents, and also in emerging uses, for example as sensors or technical and protective apparel.

Silica aerogel composites with embedded fibres: a review on their preparation, properties and applications

This paper reviews the application of molecular dynamics simulations on mechanical and tribological properties of polymer composites reinforced by carbon nanotubes and graphene sheet as reinforcements. A variety of simulation studies on modelling, calculation and analysis on enhanced elastic, tensile, fracture properties of carbon nanotubes and graphene sheet/polymer composites are introduced and reviewed. The capabilities of molecular dynamics simulations on exploring inherent mechanisms on improved tribological properties of carbon nanotubes and graphene sheet/polymer composites from atomic views are particularly discussed. Different methods of surface modifications of the two nano reinforcements on further enhancing the strength of polymer composites are summarized. Summary and recommendations for potential researches are also provided. This review is intended to provide a state-of-the-art and better understanding on applications of carbon nanotubes and graphene sheet for enhancing mechanical and tribological properties of polymer composites by molecular dynamics simulations, and inspire future efforts in this area.

A review on enhancement of mechanical and tribological properties of polymer composites reinforced by carbon nanotubes and graphene sheet: Molecular dynamics simulations

3D numerical simulation for the elastic properties of random fiber composites with a wide range of fiber aspect ratios

A criterion for the normal properties of graphene/polymer interface

Compression behaviors of carbon-bonded carbon fiber composites: Experimental and numerical investigations

Mechanical behaviors and molecular deformation mechanisms of polymers under high speed shock compression: A molecular dynamics simulation study

A new multi-scale model is proposed to investigate the relationship between the mechanical properties and microstructure of fiber-reinforced silica aerogel composites. The multi-scale model consists of the aerogel model in nanometers and the composite model in micrometers. The aerogel model is generated to represent the cluster structure of silica aerogels based on a modified diffusion-limited cluster aggregation (DLCA) algorithm, in which the size-dependent interactions between the primary particles are obtained from theoretical derivations. A continuum damage constitutive model is established to represent the behavior of the silica aerogel matrix in the composite by implementing the aerogel model with the discrete element method (DEM). After that, a modified embedded element technique (EET) is proposed to generate the finite element (FE) model of the silica aerogel composite with curve fibers. This multi-scale model is used to investigate the tensile behavior of fiber-reinforced silica aerogel composites, while a comparison with experimental results is presented. The numerical results show that the primary particle size has a significant effect on the Young׳s modulus and the tensile strength of the composites. Moreover, our present model is employed to explore the relationship between the mechanical properties of the composite and the fiber characteristics, including the fiber volume fraction, length and curvature. The predictions indicate that the characteristics of the reinforcing fibers are significant for the mechanical properties of silica aerogel composites. The present multi-scale model can be extended to study the mechanical properties of other aerogel composites.

Zeshuai Yuan

Papers

3D numerical simulation for the elastic properties of random fiber composites with a wide range of fiber aspect ratios

A criterion for the normal properties of graphene/polymer interface

Compression behaviors of carbon-bonded carbon fiber composites: Experimental and numerical investigations

Mechanical behaviors and molecular deformation mechanisms of polymers under high speed shock compression: A molecular dynamics simulation study

Multi-scale simulation of the tensile properties of fiber-reinforced silica aerogel composites