Long-term water aging effects on the durability of alkali-treated bamboo fiber reinforced composite

This paper investigates the degradation mechanisms and mechanical properties of alkali-modified bamboo fiber composites under long-term water aging (up to 120 days) at 25 degrees C. The main findings show that alkali-treatment reduces the equilibrium moisture content of composites to 12.01 +/- 0.04% after a treatment duration of 48 h. At dry conditions, the tensile strength and modulus of composites reach their maximum values of 290 +/- 11.2 MPa and 11.5 +/- 0.61 GPa for a soaking time of 4 h, then, gradually drop to smaller values, respectively. Beyond 120 aging-days, the tensile strength of 4, 24 and 48 h-modified fiber composites considerably decreases by 66.32 +/- 0.33%, 60.99 +/- 0.26% and 81.68 +/- 0.41%, respectively. Similarly, their Young's modulus falls by 39.72 +/- 0.25%, 49.04 +/- 0.19% and 41.71 +/- 0.37%, respectively. As confirmed by SEM, this significant drop is attributed to the severe microstructural damage of fibers and matrix which is a result of the prominent differential swelling between the internal cell wall layers. However, the findings attractively reveal a slight decline of about 18.15 +/- 0.34% and 15.79 +/- 0.33% in the tensile strength of raw and 0.5-h-modified fiber composites after 120 aging-days, respectively. Likewise, their Young's modulus decreases by 18.55 +/- 0.4% and 14.47 +/- 0.28%, respectively. This good aging resistance of the raw and 0.5-h-modified fiber composites suggests that the matrix plasticization, physical expansion of fibers as well as hydrolysis reaction are the main aging mechanisms.

Automated summary

This research investigates the degradation mechanisms and mechanical properties of alkali-modified bamboo fiber composites under long-term water aging. The study found that alkali-treatment reduces the moisture content of composites and the reduction is greater with longer treatment duration. The tensile strength and modulus of composites reach their maximum values under dry conditions, and then gradually decrease. Beyond 120 aging-days, the tensile strength and modulus of modified fiber composites significantly decrease. On the other hand, the raw and 0.5-h-modified fiber composites show good aging resistance.