Modeling the Stiffness of Coupled and Uncoupled Recycled Cotton Fibers Reinforced Polypropylene Composites

Abstract

The stiffness of a composite material is mainly affected by the nature of its phases and its contents, the dispersion of the reinforcement, as well as the morphology and mean orientation of such reinforcement. In this paper, recovered dyed cotton fibers from textile industry were used as reinforcement for a polypropylene matrix. The specific dye seems to decrease the hydrophilicity of the fibers and to increase its chemical compatibility with the matrix. The results showed a linear evolution of the Young's moduli of the composites against the reinforcement contents, although the slope of the regression line was found to be lower than that for other natural strand reinforced polypropylene composites. This was blamed on a growing difficulty to disperse the reinforcements when its content increased. The micromechanics analysis returned a value for the intrinsic Young's modulus of the cotton fibers that doubled previously published values. The use of two different micromechanics models allowed evaluating the impact of the morphology of the fibers on the Young's modulus of a composite.

Keywords: Young’s modulus; micromechanics; recycled cotton fibers; stiffness.

Figure 1

Workflow of the research, including the production of cotton flock byproducts, composite mixing and material testing.

Figure 2

Young’s modulus of the coupled and uncoupled CF-PP composites against reinforcement content.

Figure 3

Neat contribution of the reinforcements to the Young’s modulus of the polymers.

Figure 4

Correlation between the experimental Young’s moduli of the composites and the computed ones by using the Tsai and Pagano model in combination with Halpin and Tsai equations: (A) Unweighted correlation; (B) correlation line adding the condition of such line going through the origin.