Acoustic performance and damping behavior of cellulose-cement composites

This paper describes the influence of morphologically altered cellulose fibers on the acoustic and mechanical properties of cellulose-cement composites. Three fiber morphologies were considered (macro-nodules, discrete fibers, and petite nodules). The main parameters studied include the normal incident acoustic absorption coefficient (α), specific damping capacity (ψ), loss tangent (tanδ), storage modulus (E′), and loss modulus (E″ = E′ tan δ). The acoustic absorption coefficient was found to increase with an increase in fiber volume for all three fiber types investigated, though "macro-nodule" fibers were found to be the most effective. Stiffness-loss relationships are reported for these composites and the behavior of cellulose-cement composites with soft cellulose fiber inclusions was found to be similar to a Voigt (series) composite model. Low volumes of fibers had a minimal effect on the loss tangent; however the stiffness was considerably reduced. Predictive equations for loss modulus as a function of fiber volume at different moisture conditions were developed. These relations compare well with the experimental values as well as the idealized Voigt composite behavior. This suggests that there is an optimum fiber volume, which maximizes the loss modulus for saturated composites while the loss modulus is practically independent of fiber volume for dry composites.