Compressive stress-strain properties of natural materials treated with aqueous NaOH

Abstract

Abstract Physical and cushioning properties of wood samples treated with various concentrations of NaOH aqueous solutions have been investigated based on compressive stress-strain curves. The shapes of curves changed essentially at NaOH concentrations above 10% as a threshold concentration. The stress-strain curves were analyzed based on the assumption that a rule of mixtures is applicable in the case of a very small range of displacement. The form factor n was also calculated. The values of n of the wood samples treated with NaOH whose concentration was higher than 10% were different from those of the wood samples treated with NaOH whose concentration was less than 10%. The shape changes, longitudinal contraction and twisting of the wood samples are related to NaOH concentration. The energy-absorption efficiency parameter E and ideality parameter I were calculated based on stress-strain curves according to the literature. Also, these parameters change above the threshold concentration of 10%. It was concluded that the cushioning properties of wood treated with alkali concentrations higher than 10% are improved. Due to the shape change of wood samples, the efficiency of energy-absorption properties is higher.