Mechanical properties and microstructure of Major and Minor ampullate silks from an orb weaving spider
Abstract
A rather extensive review of various subjects related to this experimental study has been given in efforts to garner necessary understanding from the disrelation of two capcious fields, namely spider silk biology and high-rate mechanical testing. Thus, a review of tensile Kolsky bar testing is performed, being followed by analysis of previous high-performance fiber testing. Subsequent review of environmental conditions effecting spider silk mechanical properties is performed and current understanding of silk microstructure is addressed. Assessment of fracture morphology is given, with the review concluding on discussion of previous studies which inconclusively ascertained the rate effect on mechanical properties of spider dragline silk. Following, both quasi-static and high-rate tensile properties have been determined for Major and Minor Ampullate single silk fibers derived from the orb weaving spider Nephila Clavipes. Low rate tests have been performed using a DMA Q800 at 0.001 while high rate analysis has been accomplished at 1700/s utilizing a previously established miniature Kolsky bar apparatus. Rate effects exhibited by both respective silk types are addressed and direct comparison of the tensile response between the two fibers is made. Mechanical properties of these organic silks are contrasted to currently employed ballistic fibers and a performance prediction of biomemetic silk capabilities is addressed. Analysis of the MA and MI fiber microstructure is explored by a number of techniques in efforts to determine the presence of a fibrillar core-skin architecture. Examination of fiber fracture mechanisms are probed via scanning electron microscope, revealing a globular rupture surface topography. Furthermore, MA silk is subjected to a focused ion beam in efforts to remove the outer skin housing, resulting in subsurface topography investigation. Finally, MA silk is set, infiltrated, and cut in a fashion so as to image the inner structure via Transmission Electron Microscopy, yielding a definite skin-core morphology.
Degree
M.S.M.S.E.
Advisors
Chen, Purdue University.
Subject Area
Mechanics|Entomology|Materials science
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