Thermal expansion behavior of hollow glass particle/vinyl ester composites

Ceramic particle-reinforced composites have better dimensional stability than the matrix polymer at high temperatures. In hollow-particle filled composites (syntactic foams), the coefficient of thermal expansion (CTE) can be controlled by two parameters simultaneously: wall thickness and volume fraction of particles, which are explored in this study. The CTE was experimentally measured to be up to 60.4 % lower than the matrix material with the addition of glass microballoons for the twelve compositions of syntactic foams characterized using a thermomechanical analyzer. The CTE values have a stronger dependence on particle volume fraction than the wall thickness within the range of parameters explored. The experimental trends are analyzed by using Turner's and Kerner's models modified for syntactic foams. The results from the modified Turner's model show close correlation with the experimental values with a maximum difference of +/- 15 %. Parametric studies show that syntactic foams of a wide range of densities can be tailored to obtain the same CTE value. The experimental and theoretical results are helpful in developing syntactic foams with desired properties for thermal applications.