Material Properties of Natural and Synthetic Fibers
Team Members: Morana Lundquist, Margaret Parks, and Piper Thompson
Role: Primary Investigation of Cotton Fibers and Co-Author
Fall 2023
This project primarily asked us to use a Scanning electron microscope (SEM) to investigate the material properties of a chosen material. My group and I investigated the material property differences between wool, cotton, and synthetic yarn using both a SEM and by conducting tensile testing.
Synthetic yarn (curve 1) has a steep, consistent slope, which equates to ‘stretching’. Experiences significant deformation (displacement) before failure. Fracture is an elongated slope curve down.
Synthetic
Dimpling on the surface and significant necking.
Cup and cone feature.
Made of synthetic polymer.
Overview
Tensile Testing
Using an Instron Universal Testing System to conduct tensile tests, we broke all three yarn types while recording their associated force and displacement (see right). We then removed broken fibers from the yard strand and looked at the broken end using the SEM (see below).
Wool yarn (curve 2) has a gradually increasing slope, meaning that the force required to break the wool increases as the displacement increases. Fracture is an elongated slope curve down. Does not displace (stretch) significantly before failure.
SEM Imaging
Wool
Slight necking in the fracture area.
Rought fracture surface.
Strands have many layers, each layer has a different composition.
Conclusions
Cotton yarn (curve 3) has a steeply increasing slope before swiftly and directly fracturing. Cotton has more stretch than wool yarn but much less than synthetic yarn.
Cotton
Experienced no necking.
Jagged and distinct pieces of cellulose at the break.
Fibers made of 97% cellulose, which is highly crystalline, orientated, and fibrillar.
The Force vs. Displacement curve, SEM images, and chemical structure suggest synthetic yarn experiences ductile failure, and cotton yarn experiences brittle failure.
In contrast the wool yarn has characteristics of both ductile and brittle failure. Necking and the force-displacement curve suggest ductile failure, while a rough surface factor and minimal stretching suggest brittle failure. This combination is likely due to the fact that wool fibers are made of many layers of different compositions, and each layer exhibits either brittle or ductile failure.