Dynamic behaviour of silks: Nature’s precision nanocomposites

Drodge, Daniel; Mortimer, Beth; Siviour, Clive R.; Holland, Chris

doi:10.1051/epjconf/20122603007

Cited by 2 publications

(3 citation statements)

References 19 publications

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“…This method for testing soft materials at high rates of deformation, based on the quartz crystal methodology of Chen et al [5,14], improves upon previous work by using a different piezoelectric material. The method presented here uses lead zirconium titanate (PZT) 1 , which is over 100 times The two materials have equivalent strengths: 500 MPa in compression 2 .…”

Section: High Rate Compressionmentioning

confidence: 99%

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Stress gage system for measuring very soft materials under high rates of deformation

Kendall

Drodge

Froud

et al. 2014

Meas. Sci. Technol.

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Soft materials have seen continued growth in industrial importance, but are difficult to test at relevant, particularly at high, rates of deformation and relevant temperatures. This is mainly due to the low stresses supported by these materials, which mean that very sensitive force measurements are required. In this paper, a split-Hopkinson pressure bar method for testing very soft materials and elastomers at high rates of deformation is presented and applied. Experiments are conducted in compression on hydroxyl terminated polybutadiene, a very soft rubber, at strain rates of about 2000 s−1. Titanium alloy bars are used, and in addition to the usual strain gauges on the bars, forces at both ends of the specimen are measured using a piezoelectric material, lead zirconium titanate (PZT), which is much more sensitive than the quartz crystal gauges typically used in previous literature. The piezoelectric constant of PZT ranges between 290–630 × 10−12 C N−1, making it 100 times more sensitive than quartz crystal (2.3 × 10−12 C N−1). Results obtained from the experiments show that the gauges are able to measure the forces on both ends of the specimen with excellent signal to noise ratios.

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Section: High Rate Compressionmentioning

confidence: 99%

“…Soft materials continue to grow in their industrial importance, and a better understanding of their behavior under high rates of impact is essential for further use, as seen in novel biomedical applications such as synthetic tendons, or in the aerospace and defense industries in order to dampen impact [1,2].…”

Section: Introductionmentioning

confidence: 99%

Stress gage system for measuring very soft materials under high rates of deformation

Kendall

Drodge

Froud

et al. 2014

Meas. Sci. Technol.

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“…As with this phenomenon, the curvature can be shown to be a function of the distributed transverse load on the fibre, and the axial tension. We can use this model to calculate air drag from the curvature of the thread [12].…”

Section: Extended Abstractmentioning

confidence: 99%

Hierarchical Bionanomaterials Under the Hammer: High-Rate Response of Silks

Drodge

Mortimer

Siviour

et al. 2013

Mechanics of Biological Systems and Materials, Volume 4

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Silks are of significant interest to scientists and the public due to their high specific strength and unsurpassed toughness. The study of their properties and formulation of physically-based models is ongoing in the biomaterials community. Interesting models and simulation data are appearing in the literature but there is a paucity of experimental data at high strain-rate or high frequency. To remedy this, high strain-rate characterisation has been undertaken alongside conventional low-rate tests, under a range of conditions. The methods reported here represent large-strain, high-rate, i.e. transverse impact; and small-strain, high-rate, i.e. vibration. Both have relevance to the use of silk in nature by organisms (protection, predation and communication) and the application/imitation of silk by materials scientists. Here we report the methodology and results to date in our investigations on silkworm and orb weaver silks. Keywords Silk • Ballistics • Wave propagation • High-speed photography • Biomaterials Extended AbstractSilks are protein fibres produced by a range of arthropods, principally spiders and worms. Their properties have evolved to allow them to perform a range of biological functions, ranging from protective cocoons to structural web strands [1]. The requirement for prey capture in particular has led to superior toughness being a key property of the Major Ampullate (MA) silks of orb-weaving spiders, of which the Nephila family is most commonly studied. The strength of silks is often stated as superlative, but this owes more to their thin diameter than material properties [2]. Toughness is of greater interest, as energy dissipation is the key selection-driving outcome if prey is to be captured without destroying the web. Nephila fibres boast toughness of 214 MJ m À3 based on the work done to fracture [2], surpassing other silks and all other known materials [3]. Silks have been characterised extensively at low strain rates using tensile testing apparatus [4], and high strain-rate testing is a relatively new instrument in the field. Recent efforts have seen basic Kolsky bar tests used to return stress-strain data [5], and more sophisticated Brillouin scatter technique used to obtain high-frequency elastic properties [6]. Experimental investigations to date reveal some information about the physics behind the real-life energy dissipation processes in silks, as deployed in webs [7]. By invoking high-rate loading conditions we can observe the degree to which material properties and air drag contribute to the response of a single thread, from which more robust interpretations of web performance may be made in the future.Ballistic impact, first reported by Smith and colleagues [8][9][10], is illustrated in Fig. 10.1. The specimen is a long thread, held under tension T 0 by a suspended weight. As a projectile strikes it at velocity V, a transverse wave propagates, giving rise to the deflection seen in Fig. 10.2.Two aspects of this image are of interest: the position of the transverse wavefront, a...

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Dynamic behaviour of silks: Nature’s precision nanocomposites

Cited by 2 publications

References 19 publications

Stress gage system for measuring very soft materials under high rates of deformation

Stress gage system for measuring very soft materials under high rates of deformation

Hierarchical Bionanomaterials Under the Hammer: High-Rate Response of Silks

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