Ballistic impact to access the high-rate behaviour of individual silk fibres

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

doi:10.1016/j.jmps.2012.06.007

Cited by 35 publications

(33 citation statements)

References 46 publications

(38 reference statements)

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“…The longitudinal wavespeed for all materials tested was calculated from the two independent experimental techniques and shows close agreement to theory, thus validating our approach (Figure a). The ballistic impact high‐rate data show some small differences when compared to the vibrometry data and theory, explained by artefacts in the way in which longitudinal wavespeed is calculated: it is dependent on the gradient of the stress‐strain curve, so small errors in the ballistic impact high‐rate stress‐strain coordinates are converted to larger errors in the modulus and wavespeed . Additionally, error may be introduced from fluctuations in cross‐sectional area .…”

Section: Summary Of Findingsmentioning

confidence: 99%

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The Speed of Sound in Silk: Linking Material Performance to Biological Function

et al. 2014

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Section: Summary Of Findingsmentioning

confidence: 99%

“…Additionally, error may be introduced from fluctuations in cross‐sectional area . A comparison of the quasi‐static and ballistic impact high‐rate stress‐strain co‐ordinates modified from Drodge et al (2012) is given in the Supporting Figure S1 …”

Section: Summary Of Findingsmentioning

confidence: 99%

The Speed of Sound in Silk: Linking Material Performance to Biological Function

et al. 2014

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“…Our analysis of the transverse wave velocity measured using this technique, and its dependence on applied tension and material constitutive response, is described in a recent paper [13].…”

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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“…The elastic impact step assumption allows the additional stress and strain due to the impact of the projectile to be calculated, and a postimpact stress state to be plotted, forming a locus of postimpact states for the material [16]. Another analysis approach was devised by Smith, which allows a notionally "impact-rate" constitutive model to be derived from a series of impacts at different velocities [17].…”

Section: Transverse Impactmentioning

confidence: 99%

Dynamic behaviour of silks: Nature’s precision nanocomposites

Drodge

Mortimer

Siviour

et al. 2012

EPJ Web of Conferences

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Abstract. Silk is often cited as a material worth imitating, due to its high strength and toughness. In order to produce a synthetic analogue, or enhanced natural version, the microstructural basis of these properties must be understood. Current understanding is that silk deforms through the detachment of nano-scale crystallites, in the manner of a damaged composite. This picture forms the basis for constitutive models, but validation data is limited to low strain-rates. Here we present a programme of research in which high-rate behaviour is studied through ballistic impact experiments. These have been applied to the silk of the Bombyx mori moth, as harvested from cocoons, and to the major ampullate thread of the golden orb weaver spider Nephila edulis. Longitudinal wave-speeds, and air drag coefficients, have been calculated for selected cases. Differences between the response of various silks and a similar synthetic fibre, nylon, are discussed, and future plans are presented.

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Ballistic impact to access the high-rate behaviour of individual silk fibres

Cited by 35 publications

References 46 publications

The Speed of Sound in Silk: Linking Material Performance to Biological Function

The Speed of Sound in Silk: Linking Material Performance to Biological Function

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

Dynamic behaviour of silks: Nature’s precision nanocomposites

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