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Visualization and quantification of stresses at the ends of short fibers embedded in epoxy resin

: May, Michael; Mohrmann, Holger; Nahme, Hartwig


Kida, K.:
3rd International Conference on Composite Material Polymer Science and Engineering, CMPSE 2019 : October 24th and 25th, 2019, Bangkok, Thailand
Durnten-Zurich: TTP, 2020 (Key engineering materials 858)
International Conference on Composite Material Polymer Science and Engineering (CMPSE) <3, 2019, Bangkok>
Fraunhofer EMI ()
carbon fibers; polymer-matrix composites; stress concentrations; optical microscopy; photoelasticity

The photoelastic effect was used to visualize and quantify stresses at the end of fibers embedded in birefringent epoxy resin. A method was proposed allowing not to only quantify the differences in main principal stress for a single loading state, but to allow monitoring the evolution of local stress throughout the micro-mechanical experiment. It was found that the ends of fibers foster the formation of shear stresses which influence the principal stress distribution. Typically, star-shaped principal stress distributions were found at the ends of fibers. Finite Element simulations of the tests were in good agreement with the experimental evidence.