MS Thesis Presentation by Timothy P. Wilde
Monday, November 15, 2004
(Dr. David McDowell, Chair)
"An Energy Based Model for the Compressive Behavior of Goose Down"
There are many products used in everyday life that are made from materials consisting of a loose network of natural or synthetic fibers. Some common examples of these materials are carpets, felts, wool and goose down. In many cases, the resilience of these materials under cyclic loading influences the product’s lifespan and value.
In most applications these products are exposed to repeated compressive loadings that eventually result in degradation and loss of performance. When tested in a piston-cylinder device, these materials usually exhibit some irreversible deformation and hysteresis; two behaviors that can be difficult to adequately capture in a model.
Goose down is one of the most desirable materials for these applications because
of its superior insulating capability and phenomenal lofting performance.
These characteristics make goose down the preferred fill material for luxury
comforters and pillows and, in turn, make it extremely valuable in the consumer
market. Despite the value of goose down in the consumer market, very little
work has been done to study its mechanical properties, understand the underlying
mechanisms, and develop an associated model. This thesis focuses on developing
a model for the compressive behavior of goose down. First, the morphology
of goose down is explored in order to gain insight into the key mechanisms
that influence its compressive response. Assumptions regarding the influence
of the down structure on performance are then incorporated into a strain-energy
function which can be implemented into a modified hyperelastic constitutive
framework to determine the principal stresses of the material while capturing
the hysteresis and irreversible deformation observed in piston-cylinder tests.