STUDIES OF HIGH STRENGTH POLYPROPYLENE: THE ORIGINS OF DYNAMIC RESPONSES
NORTH CAROLINA STATE UNIV AT RALEIGH
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The report outlines research undertaken to identify a set of microstructure elements present in strong organic fiber in which reside the primary means of response on the part of the material to dynamic load application. The elements involve two microfibrillar concepts, viz., a set of nearly parallel structures and a set of finer transition fibrils which bridge between the former under conditions of nearly axial alignment. Scanning electron micrographs of the structural features are reported. The transition fibril is reported in one experimental setting to exhibit evidences of a labile chemical structure under exposure to ultraviolet radiation in the presence of halogens room temperature. A second principal contribution involves the statistical theory of the strength of a parallel array of fiber. The model envisions individual filaments possessing strength properties distributed along the length in accordance with the conventional weakest-link hypothesis. A set of moment inequalities has been obtained which shows the mean bundle strength per element in the absence of interaction between the constituent elements to be progressively degraded as the bundle size increases.