Meeting Abstract

27.5  Saturday, Jan. 4 14:30  Multipurpose spider silks: the implications of web impact on vibration signalling MORTIMER, B.*; SIVIOUR, C. R.; HOLLAND, C.; VOLLRATH, F.; University of Oxford, UK; University of Oxford, UK; Sheffield University, UK; University of Oxford, UK beth.mortimer@zoo.ox.ac.uk

Spider silks are multipurpose materials optimised for both mechanical and signalling roles. A prime example is found in the orb web, where the silks have to first absorb prey impact and then transmit its location. To probe the response of silk to impact, we present work which quantifies the mechanical response of single fibres of spider silks across a range of deformation rates, from low-rate tensile testing through to high-rate ballistic impact. The rate-dependence of silk is a consequence of the inelastic (or viscous) material component, which governs the energy absorption during impact. This leads to irreversible changes in silk structure as a consequence of the high stresses involved. Hence, to explore the implications of impact damage on silk signalling, the transverse and longitudinal sound velocities in silk were measured across a range of stresses. We have shown that unlike transverse waves, longitudinal waves are consistent vibration signallers over a range of stresses. This is because longitudinal sound velocities are governed by the elastic material component. In conclusion, the combination of elastic and viscous components of silks enables dual signalling and mechanical functions. We interpret this within a wider framework of energy conservation (signalling) and dissipation roles (impact) and shall discuss the role of evolution in shaping the balance between these conflicting traits.