Hybridized polymer matrix composite

Under certain conditions of combined fire and impact, graphite fibers are released to the atmosphere by graphite fiber composites. The retention of graphite fibers in these situations is investigated. Hybrid combinations of graphite tape and cloth, glass cloth, and resin additives are studied with resin systems. Polyimide resins form the most resistant composites and resins based on simple novolac epoxies the least resistant of those tested. Great improvement in the containment of the fibers is obtained in using graphite/glass hybrids, and nearly complete prevention of individual fiber release is made possible by the use of resin additives

Light weight polymer matrix composite material

A graphite fiber reinforced polymer matrix is layed up, cured, and thermally aged at about 750 F in the presence of an inert gas. The heat treatment improves the structural integrity and alters the electrical conductivity of the materials. In the preferred embodiment PMR-15 polyimides and Celion-6000 graphite fibers are used

Thermal Expansion and Diffusion Coefficients of Carbon Nanotube-Polymer Composites

Classical molecular dynamics (MD) simulations employing Brenner potential for intra-nanotube interactions and Van der Waals forces for polymer-nanotube interfaces are used to invetigate the thermal expansion and diffusion characteristics of carbon nanotube-polyethylene composites. Additions of carbon nanotubes to polymer matrix are found to increase the glass transition temperature Tg, and thermal expansion and diffusion coefficients in the composite above Tg. These findings could have implications in CNT composite processing, coating and painting applications.Comment: 11 pages, 5 figures, recently submitted for publicatio

Double walled carbon nanotube/polymer composites via in-situ nitroxide mediated polymerisation of amphiphilic block copolymers

Because of their unique physical, chemical, and structural properties, carbon nanotubes (CNT) are playing an increasingly important role in the development of new engineering materials [1]. Across many different applications, CNT/polymer composites have been extensively studied [2] S.B. Sinnot and R. Andrews, Carbon nanotubes: synthesis, properties, and applications, Crit Rev Solid State Mater Sci 26 (2001), pp. 145–249.[2]. The key problem for CNT/polymer composite elaboration is the dispersion, compatibilization, and stabilization of the CNT in the polymer matrix. To solve this problem, a structure with di-block copolymers, one with a good affinity to CNT (monomer M1), the other being the matrix (monomer M2), is proposed in this study, as shown on the two steps mechanism of Fig. 1

The surface properties of carbon fibers and their adhesion to organic polymers

The state of knowledge of the surface properties of carbon fibers is reviewed, with emphasis on fiber/matrix adhesion in carbon fiber reinforced plastics. Subjects treated include carbon fiber structure and chemistry, techniques for the study of the fiber surface, polymer/fiber bond strength and its measurement, variations in polymer properties in the interphase, and the influence of fiber matrix adhesion on composite mechanical properties. Critical issues are summarized and search recommendations are made

Non destructive examination of composite structures using dielectric examination

Dielectric measurements are widely used in the laboratory to probe the dynamics of molecules, particularly the dynamics of polymer molecules. The dielectric technique exploits the fact that many molecules, although electrically neutral posses an asymmetric distribution of charges which can be approximated to an electric dipole. The (usually thermal) motion of the molecule can be detected by the interaction of this dipole with a time varying electric field. The great advantage of the technique is that no transducers or sensors are required; the direct application of an electric field produces a directly measurable electric response over a frequency range of MHz to GHz. This paper discusses the practical application of dielectric measurements to composite structures and the information that can be obtained on the state of the polymer in polymer composite matrix materials

Influence of matrix toughness and interfacial strength on the toughness of epoxy composites with ductile steel fabric reinforcement

In the last decades, several studies have been performed on polymers reinforced with steel cords or wires. However, the diameter of these steel reinforcements was still quite large (200 micron and more). Recently, stainless steel fibers were developed with a diameter down to 30 micron, which makes it possible to process steel fiber-reinforced composites in a similar way as carbon or glass fiber-reinforced composites. If a proper combination of the ductile steel fiber and a ductile polymer is chosen, a ductile composite should be achieved. This paper reports on the influence of the matrix toughness and the fiber/matrix adhesion strength on the ductility of the resulting steel fiber reinforced textile composite. Tensile tests have been combined with microscopic analysis to investigate the relation between the mechanical behavior and the observed damage morphology. It was found that distributed damage increases the toughness in a textile composite, because it softens the transversal structure that interlocks the ductile load-bearing yarns. This explains the counterintuitive observations regarding the influence of the matrix ductility and the fiber/matrix adhesion strength on the composite toughness. It was found that selecting a brittle epoxy matrix can lead to a ductile composite, because of the widely spread and dense cracking pattern that allows more strain to the ductile steel fibers. If the fiber-matrix adhesion is enhanced by introducing a silane coupling agent to the fiber surface, transversal cracks are prevented and the ductility of the composite drops drastically. These results for the textile composites are contrary to earlier findings on the UD and cross-ply counterparts

Crashworthiness modelling of hierarchical short glass fibres reinforced graphene polymer composites materials

This work aims to analyse the response under crashworthiness impact of an automotive crash box composite consisting on short glass fibres that are embedded within graphene reinforced polymer composite. Analytical as well as finite element techniques are employed to derive the overall composite response and mechanical characterisation for a macroscopic structural crashworthiness application. Graphene sheets are considered as platelets GPL embedded within an elasto plastic polymer matrix phase leading to a 2-phases graphene/polymer composite. The modelling of 3-phases short glass fibres/graphene polymer composite consists on a double-scale approach combining the 2-phases graphene polymer composite as matrix phase in which are embedded the glass fibres. The full structure crash box is simulated at each Gauss integration point by implementing the constitutive 3-phases composite using a user-defined materials subroutine