Abstract:
Wood and wood-based composites are being used in either
new or more demanding applications. A means is needed to
successfully analyze new materials and to predict their long-term
performance. Two techniques, dynamic mechanical
analysis (DMA) and time-temperature superposition (TTS) offer
a means to accomplish this objective. The outcome of this
study is an analysis method that could be used to evaluate
the structural characteristics of wood, resin, and wood-based
composites as affected by temperature, frequency, and
humidity, and the possibility of using this information to
define changes in the production process or product.
Dynamic mechanical analysis characterizes a material's
properties in terms of the deformation response to periodic
forces. To accomplish this analysis, small samples of
material were subjected to sinusoidal loads in the center
point while the temperature was varied in a controlled
manner. The dynamic mechanical properties such as storage
modulus, loss modulus, and internal friction were determined,
in addition to the glass transition temperature, all as a
function of temperature, frequency and moisture content.
The applicability of dynamic mechanical analysis (DMA)
and time-temperature superposition (TTS) was investigated.
The time-temperature superposition principle provides a much
broader effective range of frequency by making measurements
of the dynamic properties at different temperatures and by
shifting the data to construct a master curve. Verification
studies confirmed the applicability of DMA/TTS.
Dynamic properties of wood and its components of
earlywood and latewood were measured. The data was used to
successfully predict the properties of wood. The properties
of particulate wood-based composites indicate that adhesives
play an important role in the temperature dependence of the
dynamic properties of wood-based composites. The
relationship between dynamic internal friction and static
internal bond strength was also investigated. The internal
friction measurement is suggested as a potential bonding
characterization of wood-based composites.
