engleski

Mechanical properties of flax fibers/epoxy composites for marine application

One of the critical concerns regarding the acceptance of flax fibers/polymer bio-composites for marine application, as an alternative to GFRP, are their mechanical properties. A good impregnation of fibers and adhesion between components are necessary for the load transfer from matrix to fibers. Epoxy based composites with flax fibers are prepared by means of vacuum infusion. The matrix and fibers materials are purchased by Sicomin, France and Bcomp, Switzerland, respectively. The epoxy resin of type InfuGreen 810 has 38% bio-based carbon. The ampliTex 5042 twill made of flax fibers has 500 g/m2. The fibers are industrially treated in order to improve the adhesion between the matrix and the fibers. Mechanical properties, tested in preliminary study, were not improved when fibers were further treated with solutions of 2 to 15% NaOH in distilled water. Composites with 4 to 10 layers of fibers were prepared and samples were cut with a water jet. The apparent interlaminar shear strength , tensile and flexural modulus E and strength  were tested by means of the universal testing machine Shimadzu with frame capacity up to 50 kN (Table 1). The results are compared with Rules for the classification of ships, Part 24 - Non-metallic materials, published by Croatian Register of Shipping (CRS). The Rules only include properties for GFRP, and they are given in Table 1. Any alternative material is not predicted in the rules. The composites have excellent tensile properties ; however flexural tests resulted in slightly lower values than given by the CRS. Three points bending tests were applied on both and f. The major difference in setup is that the distance between supports for is much smaller than that for f (l=5h vs. l=16h, where h is the average thickness). Composites with more than 7 layers of fibers have above 41 m.% of fibers, additionally there might be a problem with impregnation of fibers, when more layers are included. Their elongation at break is also higher, which might be a consequence of a lower cross-linking degree. Further investigation of composites with lower fibers fraction is needed.

bio-composites, flax fibers, epoxy, mechanical properties, marine application

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