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The magnitudes of the color changes in heat-treated wood are closely related to the chemical composition of the wood, and changes in the chemical composition are the essential reasons for changes in the mechanical properties of heat-treated wood. The response relationships among the color parameters of heat-treated wood and the chemical composition were constructed to provide a scientific basis for regulating the mechanical properties with the color. The effects and linear correlations of the lightness indicators (L*) for poplar (Populus tomentosa Carr.) and spruce (Picea asperata Mast.) after heat treatment were related to the chemical compositions of the heat-treated woods by constructing relationships between the L* values. The relative content of cellulose in the heat-treated poplar downward trend and was significantly positively correlated with the L* value; however, the correlation with the L* value for the heat-treated spruce was insignificant. The L* value of the heat-treated wood was significantly positively correlated with the relative contents of hemicellulose, and was significantly negatively correlated with lignin. The L* value of the heat-treated wood had a superior response relationship with the crystallite sizes. Therefore, the constructed response relationship provides a theoretical basis for accurate and nondestructive testing of the mechanical properties of heat-treated wood by using the color parameters as rapid detection indicators. [ABSTRACT FROM AUTHOR]

The creep of bamboo scrimber is an important factor to be considered in engineering applications. Simply using the creep test method not only consumes a lot of time and money, but also cannot be extended to the full stress level. Therefore, in this paper, the short-term creep tests of bamboo scrimber under different stress levels (30% and 40%) and ambient temperatures (30°C–70°C) were carried out. The multicomponent Kelvin-Voigt model and generalized Maxwell shear relaxation model of bamboo scrimber were established. The Maxwell-3 shear relaxation model was used as the constitutive model of bamboo scrimber, and the creep finite-element model of bamboo scrimber under parallel-to-grain compression was established, which verified the creep constitutive model of bamboo scrimber. The results showed that the shear relaxation modulus exhibited a significant decrease during the unstable creep stage, reaching a maximum reduction of 62.0%. It showed nonlinear for the effect of ambient temperature on the compression creep of bamboo scrimber, and the creep rate near the glass transition temperature was significantly higher than that at other temperatures. The fitting coefficients, R -square of creep compliance models, were sorted as KV-4 and KV-5>KV-3>Burgers>KV-2. The fitting coefficients, R -square of the generalized Maxwell model of shear relaxation modulus, were sorted as Maxwell-4 and Maxwell-3>Maxwell-2>Maxwell-1. The simulated creep displacement error of the two specimens was 2.8% and 0.1%, respectively, which verified the accuracy of the numerical simulation method. The paper proposed creep behavior and a constitutive model for bamboo scrimber under parallel-to-grain compression, which holds significant theoretical implications for its widespread application. [ABSTRACT FROM AUTHOR]

The widespread utilization of bamboo in the field of building and construction has sparked growing interests in conducting research on fire performance of bamboo. This study investigated fire performance of bamboo treated with flame retardants that possess water-soluble and environmental friendly characteristics. The synergistic effect of APP and P-N-B complexed flame retardant on flame resistance were evaluated, while absorption capacity and moisture absorption rate were also evaluated in relation to impregnation duration and solution concentration. The results indicated that absorption capacity increased with impregnation duration and solution concentration. It was observed solution concentration had a significant impact on moisture absorption for both APP and P-N-B complexed series. The ideal impregnation duration and solution concentration were found to be 6 h and 30%, respectively. Both APP and P-N-B complexed series significantly improved the fire performance of bamboo, but the latter exhibited a superior effect due to its synergistic combination of P, N and B. The FPIs of APP and P-N-B complexed series increased by factors of 2.4 and 4.1 compared to the untreated one. Both facilitated the formation of stable char layers and exerted their influence in gaseous phase through release of non-combustible gas for fuel dilution and free radicals mitigation. [ABSTRACT FROM AUTHOR]