There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

American Society for Testing and Materials

Biocomposites reinforced with natural fibers: 2000–2010

Due to their abundance, high strength and stiffness, low weight and biodegradability, nano-scale cellulose fiber materials (e.g., microfibrillated cellulose and bacterial cellulose) serve as promising candidates for bio-nanocomposite production. Such new high-value materials are the subject of continuing research and are commercially interesting in terms of new products from the pulp and paper industry and the agricultural sector. Cellulose nanofibers can be extracted from various plant sources and, although the mechanical separation of plant fibers into smaller elementary constituents has typically required high energy input, chemical and/or enzymatic fiber pre-treatments have been developed to overcome this problem. A challenge associated with using nanocellulose in composites is the lack of compatibility with hydrophobic polymers and various chemical modification methods have been explored in order to address this hurdle. This review summarizes progress in nanocellulose preparation with a particular focus on microfibrillated cellulose and also discusses recent developments in bio-nanocomposite fabrication based on nanocellulose.

Microfibrillated cellulose and new nanocomposite materials: a review

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

In carbon fiber reinforced polymer composites the onset of damage occurs at the fiber/matrix interface, where stress concentrations are the highest due to the property mismatch of the two materials. This article reports results of a modelling study indicating that carbon nanotubes (CNTs) grown on fibers are effective in suppressing stress concentrations at the fiber/matrix interface. In the case of high density CNT forests, they can even fundamentally change a profile of the interfacial stress. The study is performed using a novel two-scale finite element model of a nano-engineered composite based on the embedded regions technique.

Can carbon nanotubes grown on fibers fundamentally change stress distribution in a composite

In this study we investigate the tensile behaviour of unidirectional and cross-ply composites reinforced with ductile stainless steel fibres and modified adhesion to the epoxy matrix. Results show that annealed stainless steel fibres have a potential in designing tough polymer composites for structural applications. The stiffness of the UD composites made from these fibres is 77GPa combined with the strain-to-failure between 15% and 18% depending on the level of adhesion. Silane treatments were used to modify the adhesion. By treating the stainless steel fibres with different silane coupling agents, an increase of 50% in the transverse 3-point-bending strength was realised. Increasing the adhesion by 50% leads to a higher tensile strength and strain-to-failure in both UD and cross-ply laminates and a higher in-situ strength of the 90° plies. It also delays formation of matrix cracks and hinders growth of debonding.

Tensile behaviour of stainless steel fibre/epoxy composites with modified adhesion

The industrial sectors that use non-renewable fibres have undertaken an eco-design initiative. Having the structure to meet this new industrial need, the CELC Technical Section collaborated with its European scientific committee CSE to produce the first scientific work on natural fibre composite solutions, “Flax and Hemp fibres: a natural solution for the composite industry”. The book is co-published with JEC Group, a leader in the composite sector, and will be unveiled at the JEC Composite Show & Conferences (27-29 March). This new technical publication is the result of several years of research by the CELC’s European Scientific Committee CSE, backed up by the organised production/distribution chain and increasingly productive R&D efforts. It promotes the choice of flax and hemp fibres within the framework of an effective eco-design initiative and calls attention to the importance of an open-innovation approach to meet the needs of the industry over the medium and long term.

Ignaas Verpoest

Papers

Can carbon nanotubes grown on fibers fundamentally change stress distribution in a composite

Tensile behaviour of stainless steel fibre/epoxy composites with modified adhesion

Flax and hemp fibres: a natural solution for the composite industry

Maximising the hybrid effect in unidirectional hybrid composites

Tensile behaviour of stainless steel fibre/epoxy composites with modified adhesion Part A Applied science and manufacturing