Doctor of Philosophy (PhD)


Engineering Science (Interdepartmental Program)

Document Type



Syntactic foams are light weight particulate composites that use hollow particles (microballoons) as reinforcement in a polymer resin matrix. High strength microballoons provide closed cell porosity which helps in reducing weight of the material. Due to their wide range of possible applications such as in aerospace and marine structures, it is desirable to modify the physical and mechanical properties of syntactic foams as per the requirements of an application. Various filler materials can be used to modify the foam microstructure to attain these desired properties. Compression tests have revealed that high density syntactic foams demonstrate poor damage tolerance and low fracture strain, when compared with low density syntactic foams, which exhibit higher damage tolerance and fracture strains. The present study deals with increasing the fracture strain and damage tolerance properties of high density syntactic foams. An approach of modifying the matrix resin with the incorporation of filler particles as a third phase is adopted, resulting in hybrid syntactic foam. Two types of high performance hybrid foam composites are developed using waste tire rubber particles and low cost nanoclay particle respectively. Such highly damage tolerant hybrid foams will be useful as sandwich core material in automobile, aerospace, and marine structures. An analytical study is performed in order to observe the behavior of microballoons in syntactic foams upon loading. All hybrid foams are characterized for compressive strength and flexural strength properties. Rubber hybrid foams are further characterized for hygrothermal properties. Mechanical properties of hybrid foams are compared with those of plain syntactic foams. Changes in properties are correlated with the change in structural composition due to incorporation of rubber and nanoclay particles respectively. High magnification Scanning Electron Microscopy (SEM) is used to study microstructure of all the specimens. Change in properties of rubber type hybrid foams due to change in the size of rubber particles is studied. The dispersion and intercalation of nanoclay particles in nanoclay hybrid foams is studied using Transmission Electron Microscopy and X-ray photoelectron spectroscopy. Deformation behavior of hybrid foams and pure syntactic foams are compared and correlated to the presence of different types of particles in them.



Document Availability at the Time of Submission

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Committee Chair

H. Dwayne Jerro