Investigation on the Loss Factor of Polymers for Viscous Damping Walls Considering the Power-Law Effect

The loss factor is an important index for evaluating the damping capacity of non-Newtonian viscous polymers used in viscous damping walls (VDWs). The modulus ratio method (MRM) and the tangent of the loss angle (TLA) are commonly used to calculate this parameter. However, deviations may arise when using the MRM or TLA to evaluate the damping capacity of a polymer exhibiting the power-law effect. To resolve this problem, a simplified equation for the loss factor that considers the power-law effect (SELF-PL) was proposed based on its energy definition. Then, a series of dynamic sandwich-type shear (DSTS) tests was conducted to measure the loss factor of a polymer (Oppanol-polyisobutylene B12, abbreviated as PIB-B12) for VDWs. Based on the DSTS test data, the accuracy of the SELF-PL was verified, and the error of the MRM caused by the power-law effect was investigated. Finally, an error equation for the MRM was derived to quantify its applicable range. The strain rate amplitude is found to be the most influential factor affecting a power-law material. The loss factor of PIB-B12 decreases with increasing loading frequency, while it increases with increasing strain amplitude. The relative error of the MRM exhibits a roughly linear relationship with the power-law exponent.