Characterisation of the void volume loss of dynamically loaded structured polyurethane composites using viscoelastic modelling

A calculation method has been derived to predict the void volume loss of dynamically loaded structured composites commonly used as press belts in paper manufacturing. The method is based on a viscoelastic model that uses two serial generalised three-parameter Maxwell models and allows for predicting the void volume loss as a function of the applied external load and load rate. Optical verification of the void volume losses revealed that the method accurately calculates these volume losses that appear in the structure due to viscoelastic compression. Applying it to different composite specimen types makes it possible to quantify the influence of matrix material formulation, geometrical structure, temperature and saturation conditions on the void volume loss of dynamically loaded composites. As a result, the matrix material formulation of the polyurethane matrix is identified as the key parameter influencing the void volume loss. • Novel method developed to predict void volume loss in structured PU composites. • Method validated against optical high-speed measurements with ±3% accuracy. • First quantification of viscoelastic load rate effects on void volume loss. • Demonstrated influence of temperature, saturation and groove geometry on losses.