Title: THE EFFECT OF RESIN VISCOSITY, FORMING RATE, AND MEAN FILAMENT LENGTH ON THE FORMABILITY OF STRETCH BROKEN CARBON FIBER PREPREG
Authors: Matthew C. Egloff, Dalton Nold, Cecily Ryan, Dilpreet Bajwa, Douglas Cairns, Roberta Amendola
Abstract: Stretch-broken carbon fiber is manufactured by breaking filaments at inherent natural flaws. The resulting shorter filaments are aligned with randomly distributed breaks. When an axial load is applied to prepreg material, the shorter filaments separate by sliding past each other in the uncured resin matrix. This separation allows for a pseudo-ductile response and substantially greater elongation than the 2 % typical of continuous filaments which is also achieved with a substantially lower loading. This allows the stretch-broken material to be formed into more complex geometries. Tests performed in a novel apparatus developed at Montana State University show that the load necessary to form stretch broken material in three dimensions is strongly dependent on the local state of stress due to the shape, the resin viscosity, the loading rate, and the mean filament length. It was found that the response of the material changes during the forming process as the states of stress and the effective cross-section changes continuously. An assessment of location-dependent fiber volume showed that inconsistent or excessive thinning in complex shapes can be predicted and controlled. A predictive mathematical model of these effects will be presented and discussed.
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Conference: SAMPE 2023
Publication Date: 2023/04/17
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