Damping of micro- and nanocellulose reinforced PA610 composites and influences of moisture absorption

Abstract

Composites consisting of bio-based polyamide 610 (PA610) reinforced with micro- and nano-cellulose were manufactured by melt compounding followed by injection molding. The resulting composites had fiber sizes ranging from nanoscale to 100 µm at 2.5 %, 5 % and 10 % fiber mass fractions. These composites were mechanically characterized by tensile tests followed by scanning electron microscopy to examine the tensile fracture surface. The primary focus of the work was the damping behavior of these nanocomposites, which was found to be substantial. Damping was characterized using the damping ratio extracted from the measured decay of mechanical vibrations. Cellulose nanocrystal-reinforced PA610 at 10 % mass fraction was found to produce a 210 % increase in damping ratio compared to control PA610. Larger fiber sizes and lower mass fractions resulted in smaller, but significant, increases in damping. Comparison to cellulose reinforced polypropylene composites showed that PA610/cellulose composites produced significantly greater relative damping. Additionally, since both cellulose and PA610 are hydrophilic materials, a study was made on the effects of moisture absorption on the damping. It was found that the pronounced effect of the filler on damping was diminished by absorbed moisture and did not return after removing moisture from the samples. The origin of the damping increase and the effects of moisture were discussed in the article.