Fibers, Volume 7, Issue 11 (November 2019) – 5 articles

Dry fibers coming from garden waste, originating from Opuntia ficus indica, were introduced in amounts of either 8 or 16 wt % into a self-produced thermoplastic starch (TPS) based on potato starch and glycerol. Thermal (differential scanning calorimetry, DSC), mechanical (tensile tests), and morphological characterization with scanning electron microscopy (SEM) and performing energy-dispersive X-ray spectrometry (microanalysis) were carried out. The results indicated that the uneven distribution and variable geometry of fibers introduced led to a reduction of tensile stress and strain with respect to pure TPS. However, the positive effects of prolonged mixing and increased thickness were highlighted, which suggest the fabrication of the composite could be improved in the future by controlling the manufacturing procedure. Full article

Carbon fibers belong to the materials of high interest in medical application due to their good mechanical properties and because they are chemically inert at room temperature. Carbon nanofiber mats, which can be produced by electrospinning diverse precursor polymers, followed by thermal stabilization and carbonization, are under investigation as possible substrates for cell growth, especially for possible 3D cell growth applications in tissue engineering. However, such carbon nanofiber mats may be too brittle to serve as a reliable substrate. Here we report on a simple method of creating highly robust carbon nanofiber mats by using electrospun polyacrylonitrile/ZnO nanofiber mats as substrates. We show that the ZnO-blended polyacrylonitrile (PAN) nanofiber mats have significantly increased fiber diameters, resulting in enhanced mechanical properties and thus supporting tissue engineering applications. Full article

We report on a passively mode-locked oscillator based on an erbium-doped dual concentric core fiber combining high normal dispersion and large mode area. This large normal dispersion laser generates long pulses with 30 ps duration and 0.17 nm spectral width at 1530 nm wavelength. The source delivers an average power of 64 mW at a repetition rate of 16 MHz, corresponding to 4 nJ energy. This concept opens up new degrees of freedom in the design of mode-locked fiber lasers. Full article

The aim of the present paper is to assess the bearing performance evolution of pinned, glass-composite laminates due to environmental aging in salt-spray fog tests. Glass fibers/epoxy pinned laminates were exposed for up to 60 days in salt-spraying, foggy environmental conditions (according to ASTM B117 standard). In order to evaluate the relationship between mechanical failure mode and joint stability over increasing aging time, different single lap joints, measured by the changing hole diameter (D), laminate width (W) and hole free edge distance (E), were characterized at varying aging steps. Based on this approach, the property-structure relationship of glass-fibers/epoxy laminates was assessed under these critical environmental conditions. Furthermore, an experimental 2D failure map, clustering main failure modes in the plane E/D versus W/D ratios, was generated, and its cluster variation was analyzed at each degree of aging. Full article

The trend of research and adoption of natural plant-based fibre reinforced composites is increasing, with traditional synthetic fibres such as carbon and glass experiencing restrictions placed on their manufacture and use by legislative bodies due to their environmental impact through the entire product life cycle. Finding suitable alternatives to lightweight and high-performance synthetic composites will be of benefit to the automotive, marine and aerospace industries. This paper investigates the low-velocity impact (LVI) and flexural properties and damage characteristics of flax-carbon/epoxy hybrid composites to be used in structural lightweight applications. LVI, for example, is analogous to several real-life situations, such as damage during manufacture, feasibly due to human error such as the dropping of tools and mishandling of the finished product, debris strikes of aircraft flight, or even the collision of a vessel with another. Carbon fibre has been hybridised with flax fibres to achieve enhanced impact and flexural performance. The failure mechanisms of woven flax and flax-carbon epoxy hybrid composites have been further analysed using Scanning Electron Microscopy (SEM). It was observed from the experimental results that carbon fibre hybridisation has a significant effect on the impact and flexural properties and their damage modes. The results obtained from this study exhibited that the flexural strength and modulus of plain flax/epoxy composite increase significantly from 95.66 MPa to 425.87 MPa and 4.78 GPa to 17.90 GPa, respectively, with carbon fibre hybridisation. This significant improvement in flexural properties would provide designers with important information to make informed decisions during material selection for lightweight structural applications. Full article