Improvement of the mechanical property profile of NF composites by hybridization with basalt fibers
In the recent times, increasing awareness in the field of sustainability and environment protection has led to new material and technology developments in order to reduce the consumption of mineral resources. Natural fibers such as hemp, flax and kenaf applied as reinforcement in composites are one of such interesting materials that in addition to environmental friendliness show excellent technical and economical properties. The main advantage of natural fibers is their outstanding lightweight construction potential due to their low density. Additional benefits related to natural fibers are their low abrasion resistance, high toughness, enhanced energy recovery, excellent crash and damping behavior and biodegradability.
Despite their convincing technical and ecological properties, the use of natural fiber composites is mainly restricted to the semi-structural applications, since they do not achieve the same level of mechanical properties as synthetic fiber reinforced composites. Some attempts have been done to improve the properties of such composites by hybridizing bast fibers with glass or carbon fibers. Although the mechanical properties can actually be improved, the content of renewable raw materials is thereby sacrificed.
The current research work presents an attempt to improve the mechanical properties of standard natural fiber reinforced composites by hybridizing bast fibers with basalt fibers, natural mineral fibers produced from basaltic rocks. Basalt fibers not only show a very good property profile being 100 % natural. They can also be recycled since in the manufacturing process no additional components or additives are added to the melted basalt rock. Furthermore, basalt fibers are inert and have been classified as non-toxic and non-carcinogenic. As high performance reinforcements, basalt fibers have opened new doors for the use of natural fibers in technical applications since they have an excellent potential to extend the property profile of bast fiber reinforced composites without changing their renewable content.
Within this work, several composites based on polypropylene and acrylate thermoset resin, reinforced with bast fibers, were prepared as reference. In the next step 50 wt.-% of the bast fibers were replaced by basalt fibers. The compression-molded samples were tested and compared for their flexural, tensile, and impact energy properties. The results showed that the addition of basalt fibers not only significantly improved the strength and stiffness of the hybrid materials, but also simultaneously increased the energy absorption between 50 % and 75 %, depending on the composite.