Characterization of syntactic foams and their sandwich composites: modeling and experimental approaches
Hollow particle filled polymers known as syntactic foams are lightweight and highly damage tolerant. Syntactic foams are used as core materials in sandwich composites. The use of such materials in aeronautical and space structures make it necessary to understand their characteristics for various environmental and loading conditions. The first part of the present work takes modeling and finite element analysis approach to understand and predict the deformation behavior of syntactic foams. Contact analysis is performed on single particle models by the finite element analysis approach. In the second part extensive experiments are carried out to characterize syntactic foams for hygrothermal and compressive properties, and syntactic foam core sandwich composites for compressive and flexural properties. Flexural tests are carried out in three and four point bending and short beam shear configurations. Syntactic foams are tested in three different specimen sizes and orientations to characterize them as per the recommendations of various ASTM standards. Effect of specimen aspect ratio on the measured mechanical properties can be determined by such an approach. The effect of change in the internal radius of hollow particles, called cenospheres, on mechanical properties is studied for all these loading conditions. Five different types of cenospheres are selected for the study of the internal radius dependence of mechanical properties of syntactic foams and their sandwich composites. All selected types of cenospheres have the same outer radius, however, their internal radius is different. Hence, difference in mechanical properties of syntactic foams is caused due to a difference in only one parameter, the cenosphere internal radius. Such unique approach made it possible to identify the individual contribution of matrix resin and cenospheres in the mechanical properties of syntactic foams. Specimen deformation behavior and fracture features are correlated to deformation curves obtained during the testing.
flexural testing, syntactic foam, cenosphere, radius ratio, compression testing
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Engineering Science (Interdepartmental Program)