In recent years there has been a substantial growth in the use of natural fiber reinforced composite in more advanced applications. However, high strength applications require high mechanical properties. Hybridization of natural fibers with synthetic fibers is an effective method of increasing the field of application and mechanical properties. The effects of hybridizing hemp (Cannabis sativa L.) fiber with recycled-carbon fiber were investigated in this study to determine the trends in mechanical properties resulting from varied weight fractions. Characterization of void content was accomplished using micro computed tomography (micro-CT). Through hybridizing hemp fiber and recycled carbon fiber in a polypropylene thermoplastic, a new class of high performance, low cost composites were demonstrated for injection molding applications. This study showcased a 10-15% increase in tensile strength after the reinforcement of recycled-carbon fiber with hemp fiber. A 30-35% increase was observed in the flexure strength after the reinforcement of recycled-carbon fiber with hemp fiber. Impact strength also had an increase of 35-40% for hemp fiber reinforced recycled-carbon fiber polypropylene composites.Sustainability 2019, 11, 3163 2 of 12 found that composites prepared by extrusion followed by injection molding exhibited high flexural strength and stiffness [6].Carbon fiber has already gained significant acceptance in automotive and aerospace industries. Carbon fiber is an expensive material and out of reach for many industries. Therefore, recycling carbon fibers and mixing them with thermoplastic offers an affordable alternative [7]. Reducing waste and reusing materials with high-embedded energy and recycled in an energy-efficient manner is environmentally and sociably desirable. Recycled-carbon fiber retains many of its inherent advanced properties, even though it has been reclaimed from waste. In addition, the price of recycled carbon fiber is at least half than that of virgin carbon fiber [8].Several researchers examined the flexure behavior of short recycled carbon fibers (rCF) which were mixed with flax fiber in the PLA matrix. Experimental data showed that the flexural properties increased with higher rCF content, with the maximum being a flexural modulus of approximately 14 GPa and flexural strength of 203 MPa [9].There are many different possible fiber combinations for high stiffness applications. Several researchers examined the hybrid effect for flax and rCF with thermoset resin [10]. There is lack of research for the impact of hybrid effect on thermoplastic composites which use rCF blended with natural fibers [10,11]. In this study, hemp fibers were hybridized with recycled carbon fiber keeping the polypropylene matrix constant. Polypropylene was used since it can save on material cost as well as can be used as regrind without compromising the performance of the resin [12]. The total environmental impact of polypropylene is less than traditional materials in life cycle analysis [12].As an initial investigation...

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Shear thickening fluids (STFs) have been shown to improve the effectiveness of fabrics used in soft body armor applications. They are used to increase the puncture and ballistic impact resistance of Kevlar® fabrics. However, the effect of using STFs with natural fabrics such as flax appears to have never been studied. Similarly, the hybridization of different fabric types impregnated with STF has also only undergone limited study. The rheology of STFs at varying concentrations of nanosilica dispersed in polyethylene glycol (PEG) was studied at different temperatures. It was found that the STFs behave as a non-Newtonian fluid in response to changes in shear rate. In this study the effectiveness on the puncture and ballistic impact resistance of impregnating flax fabric with STF at concentrations of 30%, 50%, and 70% w/w of nanosilica in PEG was investigated. The effect of hybridization of flax and Kevlar® fabrics impregnated with STF was also investigated. The puncture resistance of both flax fabrics treated with STFs and hybrids treated with STFs was found to increase significantly and can be controlled by STF concentration. The ballistic impact resistance was also found to increase in the hybrid samples when STF concentration was at least 50%. The flax treated with STFs showed either a decrease in specific energy absorption per layer for the lower STF concentration, or a very small increase at 70% STF concentration.

Kenaf ( Hibiscus cannabinus L.) fiber is being extensively used as a reinforcement material in composites due to its excellent mechanical properties. To use this fiber more efficiently, it is necessary to understand its mechanical properties at micro/nano meter scale. Despite the evidence of some past studies to determine the elastic modulus of kenaf fiber, most of them were performed on fiber bundles. Bundle-based method to find the elastic moduli has some obvious issues of foreign materials being present, incorrect gauge length, and sample diameter due to void spaces. These issues pose as obvious hurdles to determine the elastic modulus accurately. In this study, individual kenaf micro fiber was used to find elastic modulus in the radial direction. The radial elastic modulus of the fiber was characterized by atomic force microscopy-based nanoindentation. To determine the radial elastic modulus from the force versus sample deformation data, the extended Johnson–Kendall–Roberts model was used which considered adhesion force from the fiber surface. The radial elastic modulus of the kenaf fiber was found to be 2.3 GPa.