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Structural and mechanical characterization of extrudates
Abstract
This work is an investigation of the "foam structure" of puffed, carbohydrate-based extrudates. A range of extrudates, produced to vary widely in cell structure through formulation and selection of processing parameters, were evaluated using image analysis and Instron testing. Specifically, cell size distributions were measured and described by different mathematical functions. In addition, the deformation behavior of the extrudates, which was found to conform to classic "brittle" compression models, was characterized by Fourier and Fractal analysis. And finally, the effects of various treatments on--and relationships between--structure and strength--were determined. Results of this work were that the extrudates, despite formulation or processing history, had highly skewed cell area size distributions that were closely described by both the log Normal and Rosen-Rammler models. The deformation behavior of these materials was dependent on relative humidity, and the extremely jagged nature of low RH compression curves could be quantitatively described by both the Blanket Algorithm, which determines fractal dimension, and the Fast Fourier Transform. Relationships between cell structure and mechanical properties were observed in chemically homogeneous samples produced from the same formulation (but using various process parameters) in that extrudate strength was positively associated with density and negatively associated with mean cell size. Additives also influenced extrudate properties, but the direction and magnitude of these effects depended on the specific ingredient used.
Subject Area
Materials science|Engineering
Recommended Citation
Barrett, Ann Hollenbach, "Structural and mechanical characterization of extrudates" (1991). Doctoral Dissertations Available from Proquest. AAI9207361.
https://scholarworks.umass.edu/dissertations/AAI9207361