Special Issue "Composite Materials"

Guest Editor
Prof. Dr. Ralf Riedel
Institut für Materialwissenschaft, Technische Universität Darmstadt, Petersenstr. 23, 64287 Darmstadt, Germany
Website: http://www.tu-darmstadt.de/fb/ms/fg/df/index.html
E-Mail:

Dear Colleagues,

Advanced composite materials are of particular interest in basic science as well as in applied research due to their high technological potential in the production of novel materials with tailor-made properties and with performance profiles far beyond those of the existing ones. The aim and scope of the research in this field is the development of materials with superior thermo mechanical, physical and chemical properties. The combination of different types of materials can lead to a great variety of composites, basically distinguished mainly by their constitution. Thus, the most prominent examples are denoted as polymer matrix composites (PMC), metal matrix composites (MMC) and ceramic matrix composites (CMC). In these cases, the composite comprises a matrix material in which one or more phases of another material are dispersed. The dispersed phase can be present in a variety of different morphologies such as fibers, whiskers, particles or platelets. Ideally, the resulting physical or chemical performance of the composite material is superior to that of the pure component phases. Depending on the size of the individual constituents, we distinguish between nano/nano-, nano/micro- and micro/micro-composites.

In this special issue, novel trends related to synthesis and processing suitable for the production of advanced composites as well as the property profile of their derived novel materials are highlighted and discussed.

Ralf Riedel
Guest Editor

Related Special Issues in other Journals

Composite Materials in Materials

Submission

All papers should be submitted to ijms@mdpi.org. To be published continuously until the deadline and papers will be listed together at the special issue website.

Submitted papers should not have been published previously, nor be under consideration for publication elsewhere. All papers are refereed through a peer-review process. A guide for authors is available on the Instructions for Authors page. The International Journal of Molecular Sciences is an international peer-reviewed monthly journal published by Molecular Diversity Preservation International.

Open Access publication fees are 800 CHF per paper. English correction fees and/or formatting fees (250 CHF) will be added in certain cases (1050 CHF per paper for those papers that require extensive additional formatting and/or English corrections).

• Synthesis
• Processing
• Structural and Functional Properties
• Theoretical Studies (Modeling and Simulation)
• Applications

Type of Paper: Article
Title: Composite Aerogels
Authors: T. Woignier ^1,2,* and J. Phalippou ²
Affiliations: ¹ UMR Eco&sols, IRD-PRAM, 97200, Le Lamentin, Martinique, France
² CNRS-Université Montpellier II, Place E. Bataillon, 34095 Montpellier Cedex 5, France
* Author to whom correspondence should be addressed; E-mail: thierry.woignier@univ-montp2.fr
Abstract: Aerogels have drawn increasing interest in different fields from their use in fundamental physics research to their application as specific materials. Silica aerogels are fascinating materials because of their peculiar physical properties, such as very low sound velocity [1], large specific surface area [2], low thermal conductivity [3], and fractal structure [4,5]. These peculiar features are essentially due to the very large pore volume, which can be easily tailored from 0% to 99.5%. Pore volume is controlled by the sol-gel synthesis conditions [6] and/or a sintering process [7]. The current applications of aerogels include their use as catalysts [8], insulators, [3] cosmic dust captors [9], glass precursors [7]. Another interest in these porous materials is as a host matrix for the synthesis of multi-phase materials, doped material glasses, or composites. The large pore volume is used as a sponge to incorporate chemical species in such a way as to form a two-phase material. This idea is of interest for technological application but also for theoretical research. Aerogels are ideal materials in the sense that the evolution of physical properties in relation to the structure can be experimentally studied over the whole range of porosity from 0 to 99%.
However, the counterpart of this huge porosity is poor mechanical properties, the mechanical strength, toughness and elastic modulus of silica aerogel 10^-3 lower than the data measured on dense silica , with the consequence that aerogels tend to crack when they are subjected to stresses. We propose the synthesis of a nano composite aerogels to improve the mechanical properties. silica particles (40nm) (aerosil silica soot) is added in the monomer solution, just before gelling and supercritical drying. We follow the evolution of the mechanical properties of the composite aerogels as a function of the silica particles content. The silica particles addition increases the mechanical properties, but also affects the aggregation process, the aerogel structure and the pore size distribution. Above « the percolation threshold » for concentration higher than 40%, it has been shown that the structure is made of two imbricate fractal networks, the polymeric silica and the particles silica networks. Ultra Small Angle X-ray Scattering show that besides the fractal network built up by the organosiloxane, the silica soot is forming another fractal structure at a higher scale. The fractal dimension characterizing the inorganic network could be interpreted as the signature of the linkage between the polymeric clusters. The mechanical properties rapidly increase with silica soot content strengthening the structure by a factor 5. The aerogel permeability is also improved and these nano composites aerogels have been used to synthesize new matrices for the containment of nuclear wastes [10].
References: 1. Gronauer M.; Fricke J. Acoustica 1986,59, 169.
2. Nicolaon, G.A.; Teichner, S.J. Bull. Soc. Chim. France 1968, 5, 1906
3. Fricke, J. J. Non-Cryst. Solids 1992, 147-148, 356.
4. Schaefer, D.W. ; Keefer, K.D. Phys. Rev. Lett. 1986, 56, 2199.
5. Woignier, T.; Phalippou, J.; Pelous, J.; Courtens, E. J. Non-Cryst. Solids 1990, 121, 198.
6. Brinker, C.J.; Scherer, G.W. Sol-Gel Science; Academic Press: San Diego, 1990.
7. Woignier, T.; Phalippou, J.; Prassas, M. J. Mater. Sci. 1990, 25, 3117.
8. Teichner, S.J.; Vicarini, G.A.; Gardes, G.E.E. Adv. Coll. Interface Sci. 1976, 5, 245.
9. Tsou, P. J. Non-Cryst. Solids 1995, 186, 415.
10. Reynes, J.; Woignier, T.; Phalippou, J. J. Non-Cryst. Solids 2001, 285, 353.

Type of Paper: Review
Title: Mechanical Properties of Polymer-layered Double Hydroxide (LDH) Nanocomposites
Authors: M. Ardanuy, V. Realinho and J.I. Velasco *
Affiliation: Centre Català del Plàstic. Universitat Politècnica de Catalunya, C/ Colom 114, E-08222 Terrassa, Spain
* Author to whom correspondence should be addressed; E-mail: jose.ignacio.velasco@upc.edu
Abstract: Layered double hydroxides (LDHs) are nowadays attracting considerable attention as lamellar nanometric reinforcement for polymer composites. Like clays, LDHs can be finely dispersed into polymer matrixes. This review presents a survey of the processing methods and mechanical properties of these materials. Different polymer-LDHs composites are reviewed, especially those prepared with thermoplastic polymers (PE, PP, PS, PMMA, etc). For these materials, some structure-mechanical properties relationships are identified and discussed, and compared with those of polymer-clay nanocomposites.

Type of Paper: Article
Title: The Effect of Water Absorption on the Physical, Flammability and Mechanical Properties of Polymer Eco-Nanocomposites
Authors: H.Alamri, A. Alhuthali and I.M. Low
Affiliation: Department of Imaging & Applied Physics, Curtin University of Technology, GPO Box U1987, Perth, WA 6845, Australia
Abstract: When compared to their synthetic counterparts, natural fibres represent an environmentally friendly alternative by virtue of several attractive attributes that include lower density, lower cost, non-toxicity, ease of processing, renewability and recyclability. In addition, the use of natural fibres in polymer matrix composites has the potential to produce materials with higher specific strength and specific modulus due of their low density. In this paper, epoxy and vinyl-ester resin matrix composites reinforced with recycled cellulose fibre (RCF) have been fabricated via different preparation processes. Nano-composites from both polymers reinforced with nano-fillers such as nano-clay platelets and halloysite nano-tubes (HNT) have been synthesized. The effect of water absorption on the physical, flammability, and mechanical properties of these eco-nanocomposites has been evaluated using differential thermal analysis, Vickers indentation, flammability, Charpy impact and three-point bend tests. The effect of nano-dispersion on the physical and mechanical properties before and after water absorption will be discussed.

Type of Paper: Review
Title: Quantum Chemistry, Physical Chemistry, Molecular Dynamics Simulation, DFT (Density Functional Theory), and Coarse-Graining Techniques Applied in Structural, Cellular Biology, Polymer Science and Implication for Scaleportation
Authors: V. S. Travkin and N. N. Bolotina
Affiliations: Hierarchical Scaled Physics and Technologies (HSPT), Los Angeles, CA, USA
Abstract: There is no substance of physical volumetric content in our known universe that is not a heterogeneous one. The thing is to determine at which scale it becomes as that, at the atomic, planetary, stellar, sub-particle, or other known scale?
The current trend is that almost all technical fields can be characterized by attention and claims to the physically multiscale description of problems.
Among many scientific techniques used nowadays we consider the following as scale depending:
1) Quantum Chemistry;
2) Physical Chemistry;
3) Molecular Dynamics Simulation;
4) Density Functional Theory (DFT);
5) Coarse-Graining Techniques.
Totally, these fields must provide for the ladder of spatial and temporal scales, physical models that could match one to another at the interface between the neighboring scale fields. There are many pictures that have been developed for the illustration.
Scaleportation was introduced some years ago as a definition for the means and procedures of the direct and strict "transformation" of data at one scale to the data of the neighboring Upper or Lower Scale. These interscale communications, scale transformations of data are mainly not by formulae, but most often using the scaled governing equations for the phenomena. In this review we take into consideration one scale features of the above mentioned theories and their potentials for scaleportation to the neighboring scales.