  In this paper, a fundamental understanding of the densification mechanics of
polymeric syntactic foams under compressive loading is established. These
syntactic foams are closed cell composite foams with thin-walled microballoons
dispersed in a matrix (resin) whose closed cell structure provides excellent
mechanical properties, like high strength and low density. There are several
parameters that can contribute towards their mechanical properties, including,
microballoon volume fraction, microballoon wall thickness, bonding between the
microballoons and the matrix, and the crushing strength of microballoons.
Conducting purely experimental testing by varying these parameters can be very
time sensitive and expensive. Also, identification of densification mechanics
is challenging using experiments only. Higher densification stress and energy
are favorable properties under foam compression or crushing. Hence, the
influence of key structural and material parameters associated with syntactic
foams that dictate the mechanics of densification is studied here by
implementing micromechanics based computational models and multiple linear
regression analysis. Specifically, specific densification stresses and energy,
which are densification stresses and energy normalized by weight, are evaluated
which are more relevant for a wide variety of weight saving applications.
Microballoon crushing strength and volume fraction are identified as the
parameters that have the higher influence on densification stress and energy,
and their specific counterparts, whereas the interfacial bonding has the least
impact. In addition, designing aspects of syntactic foams with specified
overall density are discussed by mapping microballoon volume fraction and wall
thickness.
