9. Dynamic Mechanical Properties

Studying the influence of temperature and loading frequency on the behavior of syntactic foams is important because of its diverse set of applications. Dynamic mechanical analysis (DMA) is a widely used technique for measuring viscoelastic properties of materials over a range of temperatures and loading frequencies. The storage modulus and loss modulus determined in a DMA experiment measure the capacity of a material to store and dissipate energy, respectively. In general, the storage modulus of syntactic foams decreases with increasing temperature. This response was consistent between plain and reinforced syntactic foams. Study of storage modulus of vinyl ester/glass hollow particle syntactic foams at three different temperatures concluded that the neat resin has higher storage modulus than the syntactic foams below glass transition temperature (T _g) but this trend is reversed above T _g. Also, the room temperature (30 °C) storage modulus of syntactic foams increases with the increase in the wall thickness of hollow particles. The addition of nanoclay increased the storage modulus of epoxy matrix syntactic foams. The effect was attributed to the toughening of matrix resin by nanoclay particles. However, increased stiffness of nanoclay reinforced syntactic foams resulted in decreased loss modulus. Cyanate ester matrix syntactic foam with 4 vol. % of nanoclay showed higher storage modulus than the plain syntactic foams, owing to the restricted movement of the polymer chains which can be attributed to the good interaction between the nanoclay and the matrix resin.