Analysis of high volume fraction irregular particulate damping composites

Concentrated suspensions of inclusions occur in asphalt and dental composite resins. Concentrated suspensions are also of use in achieving a combination of high stiffness and loss (the product E tan delta), desirable in damping layer and structural damping applications. For realizable particulate microstructures, analytical solutions for monodisperse inclusion morphologies such as spherical, random fibrous and platelet, are valid only in the case of a dilute concentration of inclusions. Finite element analyses were conducted of hierarchical particulate composites with high volume fractions of particles of irregular shape. For particle volume concentration 40 percent or less, the results are close to the Hashin-Shtrikman lower formula in a stiffness versus concentration plot and in a stiffness loss map. For larger concentration, stiffness is higher and E tan delta is lower The irregular particle shape therefore enhances stiffness at a given concentration, and reduces damping layer performance.