Uniform TitleFlexural properties and characterization of geopolymer based sandwich composite structures at room and elevated temperatures
NameSimonovic, Milan (author), Pelegri, Assimina (chair), Tse, Stephen (internal member), Lin, Hao (internal member), Rutgers University, Graduate School-New Brunswick,
SubjectMechanical and Aerospace Engineering,
DescriptionThis thesis is an experimental study on structural changes and change of the mechanical properties of geopolymer-based sandwich structures. Specimens were prepared combining a potassium aluminosilicate geopolymer base, perlite filler and three different mass ratios of cenosphere material. Prepared specimens were left to age for four weeks at room temperature, before a reinforcing skin layer was added. The reinforcing layer was produced with one or two tows of ceramic or carbon fibers. Samples were divided into several groups and exposed to different temperatures: from room to one-hour exposure at 750° C. After temperature treatments, the samples were subjected to a three-point bending test and flexural properties were determined. SEM microscopy was used to examine the following features: contact properties between the geopolymer base and fillers, adhesion between the reinforcement fibers and core and micro structural changes in material caused by high temperature and loading conditions. It was determined that adhesion among the geopolymer material, fillers and fibers was very good. Cracks, which appeared after temperature treatment and flexural tests, usually progressed through lower-density areas (like undamaged perlite particles, voids or other imperfections) and higher-porosity areas of the geopolymer cenosphere mixture. The flexural strength of unreinforced samples was low (between 1-12 MPa). It was determined that thermally treated samples show a drastic decrease (60-65%) in residual flexural properties. After temperature treatment, significant sample deformation was observed. The SEM revealed that micro structural changes were significant, including increase in pore size, volume expansion, cracking and perlite and geopolymer material expansion. It was noticed that the maximum strength of sandwich structures falls with an increase of cenosphere mass ratio, but flexibility and material toughness increase. Tensile failure of the bottom reinforcing layer was the primary failing mechanism for the majority of tested samples. During thermal exposure, some samples experienced severe cracking and deformation, which caused premature (tensile) failures and other failure types (like core shear). It was concluded that the thermal stability of the tested material and structures was inadequate, that structural applications would not be recommended and that refractory applications would be limited.
Note[bibliography] Includes bibliographical references (p. 104-107).
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.