An alternative method to evaluate the micromechanics tensile strength properties of natural fiber strand reinforced polyolefin composites. The case of hemp strand-reinforced polypropylene

Abstract

Micromechanics models allow the prediction of a composite material's properties by adding their phases' contributions to such properties. The models can be used to obtain the intrinsic properties of the reinforcements because are difficult to obtain experimentally. This paper explores a simplified model to obtain the intrinsic strength of natural fibers. This model allows obtaining the value directly from the experimental strength of a composite and the matrix. Other models like the Kelly and Tyson equation have three unknowns, needing the use of mathematical methods to obtain a solution, and the obtained solution sometimes deviates from the expected values for natural fiber-reinforced composites. The proposed equation has been able to evaluate the intrinsic strength of hemp fibers as polypropylene composites at a mean value of 600 MPa. This value agrees with the literature. The proposed method simplifies the obtention of the intrinsic tensile strengths of natural fiber reinforcements and does not need morphologic properties of such reinforcements to obtain a solution, decreasing the costs in time and equipment in comparison to usual models like Kelly and Tyson's. furthermore, the obtained results are like those obtained with other micromechanics approaches and reveal the same information about the intrinsic tensile strength of the reinforcements and the strength of the interface

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