Strong and Tough Silk for Resilient Attachment Discs: The Mechanical Properties of Piriform Silk in the Spider Cupiennius salei (Keyserling, 1877)

Mirbaha

Schmuck

et al. 2022

Sci Rep

Self Cite

Silk fibres attract great interest in materials science for their biological and mechanical properties. Hitherto, the mechanical properties of the silk fibres have been explored mainly by tensile tests, which provide information on their strength, Young’s modulus, strain at break and toughness modulus. Several hypotheses have been based on these data, but the intrinsic and often overlooked variability of natural and artificial silk fibres makes it challenging to identify trends and correlations. In this work, we determined the mechanical properties of Bombyx mori cocoon and degummed silk, native spider silk, and artificial spider silk, and compared them with classical commercial carbon fibres using large sample sizes (from 10 to 100 fibres, in total 200 specimens per fibre type). The results confirm a substantial variability of the mechanical properties of silk fibres compared to commercial carbon fibres, as the relative standard deviation for strength and strain at break is 10–50%. Moreover, the variability does not decrease significantly when the number of tested fibres is increased, which was surprising considering the low variability frequently reported for silk fibres in the literature. Based on this, we prove that tensile testing of 10 fibres per type is representative of a silk fibre population. Finally, we show that the ideal shape of the stress–strain curve for spider silk, characterized by a pronounced exponential stiffening regime, occurs in only 25% of all tested spider silk fibres.

Section: Resultsmentioning

confidence: 99%

“…1 and then obtaining the parameter α . In this sense, we also used previously published data (in open access) for other species, and in particular from their stress–strain curves 3 , 25 , 26 .…”

Section: Methodsmentioning

confidence: 99%

Artificial and natural silk materials have high mechanical property variability regardless of sample size

Mirbaha

Schmuck

et al. 2022

Sci Rep

Self Cite

“…Finally, the ultimate strength was obtained by taking the final engineering stress prior to fracture. All silk threads were tested two weeks after their production to stabilize the concentration of residual stresses and thus to minimize their effects on the mechanical properties [48][49][50]. All samples were kept in controlled conditions (20-21 • C and 39-42% RH) during this period to create uniform testing conditions.…”

Section: Tensile Testsmentioning

confidence: 99%

Mechanical Properties and Weibull Scaling Laws of Unknown Spider Silks

Pugno

2020

Molecules

Self Cite

Spider silks present extraordinary mechanical properties, which have attracted the attention of material scientists in recent decades. In particular, the strength and the toughness of these protein-based materials outperform the ones of many man-made fibers. Unfortunately, despite the huge interest, there is an absence of statistical investigation on the mechanical properties of spider silks and their related size effects due to the length of the fibers. Moreover, several spider silks have never been mechanically tested. Accordingly, in this work, we measured the mechanical properties and computed the Weibull parameters for different spider silks, some of them unknown in the literature. We also measured the mechanical properties at different strain rates for the dragline of the species Cupiennius salei. For the same species, we measured the strength and Weibull parameters at different fiber lengths. In this way, we obtained the spider silk scaling laws directly and according to Weibull’s prediction. Both length and strain rates affect the mechanical properties of spider silk, as rationalized by Weibull’s statistics.

“…Moreover, the spiders of the family Theridiidae used aggregate silk to cover capture threads with glue [42]. The threads were fixed to the surfaces by means of attachment discs produced by the piriform silk (figure 3d,e) [43,44]. In all cases, the spiders under analysis built the webs with the capture threads near the bottom of the enclosure.…”

Section: Structure Of the Websmentioning

confidence: 99%

How spiders hunt heavy prey: the tangle web as a pulley and spider's lifting mechanics observed and quantified in the laboratory

Pugno

2021

J. R. Soc. Interface.

Self Cite

The spiders of Theridiidae's family display a peculiar behaviour when they hunt extremely large prey. They lift the quarry, making it unable to escape, by attaching pre-tensioned silk threads to it. In this work, we analysed for the first time in the laboratory the lifting hunting mechanism and, in order to quantify the phenomenon, we applied the lifting mechanics theory. The comparison between the experiments and the theory suggests that, during the process, spiders do not stretch the silk too much by keeping it in the linear elastic regime. We thus report here further evidence for the strong role of silk in spiders' evolution, especially how spiders can stretch and use it as an external tool to overcome their muscles’ limits and capture prey with large mass, e.g. 50 times the spider's mass.