Spectral Distribution
Representing the distribution of relaxation times at a reference temperature provides a view of how a material dissipates stress over time. Using a shifted relaxation spectrum allows for the prediction of long term creep from short term experimental data. This distribution identifies the contribution of different molecular weight fractions to the overall stiffness of the polymer.
The approach is limited to materials that follow the time-temperature superposition principle.
Prediction Capability
Using this spectrum allows engineers to transform data between the time and frequency domains. It provides a more detailed picture than a single modulus value by showing the weight of every relaxation mode.
This Adjustment
This adjustment is made by applying shift factors to the raw data collected across a range of temperatures. The resulting spectrum shows the internal dynamics of the material as if it were tested at a single temperature for an infinite duration.
Relaxation Behavior
Mechanical response at very short times is dominated by the fast relaxation modes of the polymer backbone. At longer times, the movement of entire chains determines the behavior. Accurate spectra are necessary for the simulation of complex molding processes and the performance of structural parts under sustained stress.
