Subject: SEMINAR NOTIFICATION M. Hudspeth 3/21/12
From: "Stacey, Lisa A" <[email-masked]>
To: "[email-masked]'" <[email-masked]>
Date: Wed, 14 Mar 2012 12:13:52 -0400

Please see below…

MATERIALS SCIENCE AND ENGINEERING
SEMINAR

Mechanical Properties and Microstructure of Major and Minor Ampullate Silks from an Orb Weaving Spider

By

Matthew Hudspeth
Purdue MSE Final Exam
Prof. W. Chen

ABSTRACT

Spiders produce some of the most impressive natural fibers. In particular, orb weaving spiders can generate a variety of silk fibers possessing extremely diverse physical properties. Each of these differing fibers originates from variable liquid emulsions and from multifarious glands,  ducts,  and  spigots  in  order  to  create  intricate webs,  catch  flying prey,  protect offspring via cocoons, and most importantly, to provide a safety line (dragline)  during their daily travels.  The cost of producing this organic silk is quite high, and over 400 million years spiders have evolved in a fashion so as to efficiently tailor the needed physical properties while minimizing the interior caloric cost.  Of particular interest are the two structural silks, which are derived from the Major (MA) and Minor (MI) ampullate glands, and are used by the spider in order to effectively construct the framework for its nutrient gathering snare. These silks have been shown to possess striking mechanical properties, requiring roughly the same amount of energy to break as currently employed high-performance fibers such as Kevlar.  In light of this, MA and MI silks are of great interest in structural and ballistic applications, and it is imperative from a material characterization standpoint to understand the response of such a biopolymer when tested at increasing strain rates.  Very little effort has been directed at the sensitivity of spider silk to extension rate and published data have shown highly variable effects.
Therefore, in order to access the effect of extension rate, both quasi-static and high-rate tensile properties were determined for single MA and MI fibers derived from the orb weaving spider Nephila Clavipes.   Quasi-static tests have been performed at 10−3  s−1 while high rate analysis was done at 1700 s−1 utilizing a 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.  The fibers showed major increases in toughness at the high extension rate.   Mechanical properties of these organic silks are contrasted to currently employed ballistic fibers and examination of fiber fracture mechanisms are probed via scanning electron microscope, revealing a globular rupture surface topography for both rate extremums.

Date:   Wednesday, March 21, 2012

Time:        2:30 P.M.
Place:   ARMS 1028
PURDUE MSE

Lisa Stacey
Secretary/Development Assistant
Purdue University
School of Matierals Engineering
765/494-4100