The Royal Society Publishing (London, UK) has published a paper, titled "Extreme strength observed in limpet teeth," which reports that the teeth of limpets use composite nanostructures that consist of high volume fractions of nanofibers combined with a protein phase matrix to produce an uncommonly strong material.
Authored by Asa H. Barber (University of Portsmouth, Portsmouth, UK), Dun Lu (Università di Trento, Trento, Italy) and Nicola Pugno (Università di Trento), and published Feb. 18, the paper says:
"The teeth of limpets exploit distinctive composite nanostructures consisting of high volume fractions of reinforcing goethite nanofibres within a softer protein phase to provide mechanical integrity when rasping over rock surfaces during feeding. The tensile strength of discrete volumes of limpet tooth material measured using in-situ atomic force microscopy was found to range from 3.0 to 6.5 GPa and was independent of sample size. These observations highlight an absolute material tensile strength that is the highest recorded for a biological material, outperforming the high strength of spider silk currently considered to be the strongest natural material, and approaching values comparable to those of the strongest man-made fibres. This considerable tensile strength of limpet teeth is attributed to a high mineral volume fraction of reinforcing goethite nanofibres with diameters below a defect-controlled critical size, suggesting that natural design in limpet teeth is optimized towards theoretical strength limits."
Limpet teeth are extremely small, measuring about 75 µm long, and thus were a challenge for researchers to extract, prepare and test to assess strength characteristics. According to the research, the strength of the limpet tooth is attributed primarily to geothite, an iron-bearing hydroxide mineral, which helps give the composite tooth strength properties on par with Toray (Tokyo, Japan) T1000 carbon fiber.
طبقه بندی: کامپوزیت،
برچسب ها: limpet teeth، composite، nanofibers، polymer،
The two flat roofs on either side of the central clock tower of the Southern Colonnade entrance at King’s Cross Station in London, UK, have been refurbished due to extensive sagging and leakage problems. The old bitumen-bonded felt roof that had been in place for many years was beyond repair and needed to be replaced. This refurbishment project was initiated by Network Rail, which set itself the objective of having a new flat roof installed that could be expected to last for at least 20 years.
Since even modern triple layer felt systems are typically only guaranteed for 10 years, Network Rail looked at alternative flat roofing systems to replace the bonded felt roofing. The system finally specified by Network Rail was Scott Bader’s (Wollaston, Northamptonshire, UK) CrysticROOF BBA Premier, a seamless, cold applied, liquid resin glass fiber-reinforced plastic (GRP) roofing system. The new Southern Colonnade flat roof at King’s Cross is guaranteed for 25 years by Scott Bader, since it was installed by a fully certified, approved CrysticROOF installer.
As part of the rigorous specification and product approval process, a representative from Network Rail’s Asset Maintaining Department visited Scott Bader’s UK plant in Northamptonshire, where the CrysticROOF unsaturated polyester resin and topcoat GRP raw materials were developed, and are manufactured to ISO 9001, ISO14001 and OHSAS 18001 standards and procedures. Samples of the CrysticROOF materials were also submitted to Network Rail and subjected to a variety of in-house technical tests before finally gaining approval for this project.
The CrysticROOF Premier system meets BS476 Part 3 for all roof structures and shapes including flat, valley and pitched roofs, walkways, roof-lights and balconies. When correctly applied, it is said to provide long-term ultraviolet (UV) light resistance and weathering performance, remaining watertight and maintenance-free for many years.
The CrysticROOF range of cold-applied GRP roofing products was developed specifically for new flat and pitched roof designs. It is a fully BBA approved flat roofing system, which now includes a fire resistant (FR) isophthalic topcoat as standard, helping installers and contractors avoid the risk of not meeting fire safety legislation and building regulations.
All CrysticROOF products are fully compatible with standard roofing materials commonly used for fabricating cold liquid system GRP flat and pitched roofs. CrysticROOF BBA Premier has also been accepted by the NHBC as an approved GRP roof waterproofing system to NHBC Standards 2011, Part 7 Roofs, section 7.1 for flat roofs and balconies and 7.2 for pitched roofs, provided the roof is installed, used and maintained in accordance with the BBA certification.
طبقه بندی: کامپوزیت،
برچسب ها: composite، london، rail station،
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