Simple model to predict the intrinsic flexural modulus of abaca strands from crystallinity and microfibril angle

Abstract This study presents a novel equation that obtains the intrinsic flexural modulus of a natural fiber from its microfibril angle (MFA) and its crystalline cellulose content, once having estimated both parameters from X‐ray diffraction (XRD). The percentage of crystalline cellulose was estimated as the content of cellulose times the crystallinity index. Moreover, the MFA of abaca strands was obtained through an equation relating MFA with the strain at break of the strands and by XRD azimuthal integration, obtaining similar results. Fully bio‐based composites, consisting of biopolyethylene reinforced with of abaca strands at 20 to 50 wt% contents, were tested to assess the impact of the natural fibers on the flexural modulus of the composites. The intrinsic flexural modulus was also evaluated by using three micromechanics models (Hirsh equation, Halpin and Tsai equation, and its modification by Nielsen). The values obtained from the application of the new equation, the micromechanics methods, and the literature showed satisfactory agreement. Highlights Evaluation of the flexural modulus of abaca strand reinforced bio‐polyethylene composites. Use of micromechanics models to obtain the intrinsic modulus of abaca strands. Formula that correlates the intrinsic flexural modulus of abaca to its crystalline cellulose content and microfibril angle.