Controlling the orientation and spatial distribution of
discontinuous fibers in composite materials enables product
properties to be tailored to anticipated use. Electric
fields are already (albeit rarely) used to affect alignment
in lignocellulosic (LC) fiber composites. The use of
magnetic fields has not, however, been suggested or
explored; this is apparently because LC fibers are
essentially non-magnetic. The approach may offer, however,
some considerable advantages, as long as ferromagnetism may
be imparted to the fibers.
In the present research several fiber modification
processes were considered and two, electroless nickel
plating and spray application of a coating containing nickel
in suspension, were investigated in more depth. The latter
was chosen to render highly engineered, elongated wood
particles responsive to magnetic fields. Individual treated
particles were suspended in viscous, newtonian silicone
fluids and their rotation under the influence of a
controlled magnetic field was video recorded.
The magnetic torque on the particle was, under the
above conditions, directly proportional to the fluid
viscosity, to the particle's angular velocity and to a
characteristic shape constant. The maximum of the specific
magnetic torque (magnetic torque divided by the shape
constant) was found to reflect the influence of field
strength and particle Ni-treatment on rotation. Results
were scaled to an arbitrarily chosen viscosity for
comparison.
The dependencies of the magnetic torque found in the
present research compare with those theoretically predicted
for ellipsoidal and cylindrical bodies. For field strengths
ranging from 0.07T to 0.15T (below magnetic saturation) the
magnetic torque increased almost linearly with increasing
field strength. Magnetic torque was also found to increase
nearly linearly with increasing bulk Ni-concentration (5g/kg
- 50g/kg).
Rotational motion was sometimes impeded at low field
strengths and this was attributed to a permanent magnetic
moment obtained by the particle. A coercive field strength
of 7600A/m supported this hypothesis. Judiciously switched
field polarity increased magnetic torque at small alignment
angles.
The present research indicates that orienting LC fibers
with magnetic fields is possible and promising. To study
dynamics of fiber motion in low viscosity fluids, such as
air, a different experimental method is necessary; however,
dependencies of the magnetic torque found in the present
study still hold true. / Graduation date: 1993
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36066 |
| Date | 09 November 1992 |
| Creators | Zauscher, Stefan |
| Contributors | Humphrey, Philip E. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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