Influence of fiber curvation on the carbon durability during high-speed loading | Mekhanika | kompozitsionnykh | materialov i konstruktsii
> Volume 25 > №3 / 2019 / Pages: 423-433

Influence of fiber curvation on the carbon durability during high-speed loading

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The indirect laying of reinforcing fibers in polymer composite materials can be both a consequence of technological defects and a targeted constructive solution aimed at optimizing the local characteristics of the material. Fiber curvatures can occur as technological defects in the case of lay-out errors, uneven impregnation and improper polymerization conditions, uneven shrinkage, etc. This paper presents the results of an experimental determination of the tensile strength and ultimate strains during compression of unidirectional carbon fiber specimens with straight-line (ordinary) and wave-like laying of fibers under high-speed loading. Dynamic tests were carried out according to the Kola method using a split Hopkinson rod on a high-speed system “StrainMaster High-Speed 3D DIC”. Static tests were performed on an Instron universal testing machine. The wave-like laying of fibers was created purposefully to study the effect of fiber curvature on the mechanical properties of the composite. For each type of fiber laying, a test of cylindrical samples cut in the directions of the axes of orthotropy of the material was performed. Three samples were tested for each type and each direction. For comparison, the strength of the samples under quasi-static loading was determined. As a result of the tests, a decrease in the compressive strength of the composite, in the presence of fiber curvature by 5-32%, and an increase in the high-speed strength characteristics, in comparison with quasi-static, by 30-60% were found. An increase in the ultimate strains of a composite with curved fibers under quasi-static loading has been established. The change in the nature of the destruction of the samples in the presence of fiber curvature under static and high-speed loading is investigated.