Abstract: For natural fibers reinforcing polymer composite (NFRPs), one of the topical issues is to ensure a reliable fiber-matrix interfacial bond. The subject of the experimental study was samples of microplastics from elementary fibers of the stalk of nettle (Urtica dioica L.) and an epoxy matrix. The aim of the study is to assess fiber-matrix interface of microplastic samples based on elementary nettle stem fiber and an epoxy binder. The experimental studies used the methods of micromechanical testing and optical microscopy. Elementary fibers up to 70 mm in length were isolated from the stalks of early spring nettle. To obtain microplastics, a binder based on ED-20 epoxy resin and HT-152B anhydride hardener was used. Samples of microplastics with single elementary fibers were prepared. Micromechanical tests for fragmentation of a single fiber have been carried out. The fibers were tensile tested on a tensile testing machine at a crosshead speed of 5 mm / min. The width of the cross-sections of the fibers is variable along the length and ranges from 5 to 30 microns, the size ratio (width-thickness) reaches 1:1.5. Fiber elongation during destruction of a microplastic sample is relatively small and reaches 135 μm, which corresponds to 8 to 10 times the cross-sectional dimension of the fiber along with its elongation. The minimum fragment length is 165 µm. The interfacial adhesion fiber-matrix strength can be estimated at 1.38 MPa. The nature of the fiber breaks testifies to the fragile mechanism of its destruction. It was confirmed that the fiber-matrix interface in the studied NFRPs samples is explained by the mechanism of mechanical blocking. The results of the experimental study can be used to create a NFRPs based on natural fibers and an epoxy matrix.
Index terms: microplastic, reinforcing filler, elementary fiber, nettle stalk, ED-20 epoxy resin, HT-152B anhydride hardener, fiber-matrix interface, micromechanical tests, optical microscopy, experimental research.


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