Viscoelastic properties of composites of calcium alginate and hydroxyapatite

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Calcium alginate was reinforced with hydroxyapatite (HA) particles, whose dimensions were a few micrometres, with mass fraction, mf, values in the range 0–0.8. Cylindrical samples of these composite materials were subjected to cyclic compression in the frequency range f = 0.001–20 Hz; in these tests a sinusoidal load of amplitude 1 N was applied either side of a static compression of 2 N. Storage and loss moduli, E′ and E″, respectively, were found to be independent of particle size; however, E′ increased with frequency consistent with the materials undergoing a glass transition. Above frequencies of about 0.05 Hz, E′ > E″ for all materials. For each frequency, the dependence of the moduli on log10f could be represented by a third order polynomial; these equations can be used to calculate E′ and E′′ for a range of compositions. Approximate values ofm

are predicted by a Reuss model.

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