High-quality wood resource scarcity as well as population growth and demand of wood have encouraged the use of alternative sources of lignocellulosic materials. In this study, the possibility of producing particleboard from waste cotton stalks is evaluated. The effects of the independent variables included weight ratio of melamine-formaldehyde to urea-formaldehyde, shelling ratio and the percentage of cotton stalks to poplar in the core layer were analyzed in the form of response surface methodology based on second-order multiple linear regression model. The results showed that there was perfect agreement between the estimated values and observed data, as with an increase in the ratio of melamine-formaldehyde resin to urea-formaldehyde, shelling ration and amount of poplar in the core layer of panels, modulus of rupture, modulus of elasticity and internal bonding increase. The optimal point of use of investigated variables included 18.30% melamine-formaldehyde, 30.35% thickness of the surface layers and 10.70% of poplar in the core layer.

The goal of this research is to investigate some morphological (fibre length, fibre diameter, cell wall thickness, Runkel coefficient, flexibility coefficient, slenderness coefficient, rigidity coefficient, Luce's coefficient, solid coefficient), physical (dry wood density, volumetric shrinkage) and chemical (cellulose, hemicellulose, lignin, ash and acetone soluble extractives contents) composition of Konar (Ziziphus spina-christi) wood grown in Hormozgan province, Iran. For this purpose, three normal trees were selected randomly and a disk was cut from each one at breast height. Anatomical inspection revealed that the species was diffuse porous, with distinctive growth rings, simple preformation plate, with polygonal openings, and banded or diffuse-in aggregates parenchyma. The average values of wood dry density, fiber length, fiber diameter, cell wall thickness, Runkel coefficient, flexibility coefficient, felting coefficient, Luce’s coefficient, solid coefficient, rigidity coefficient were 0.926, 52.1, 77.85, 0.57, 163 ×103 μ3 and 0.48. Cellulose, hemicellulose, lignin, acetone soluble, extractives, ashcontents were43.34, 19.98, 33.9, 6.42 and 2.78%, resp.

Expanding the service life length of wooden made furniture, and consequently decreasing the demand for raw wood could help the economy of the world society and environmental safety. In this research, an experimental inquiry was conducted to determine the effects of curved members, the frame integrity, chair scheme, and rehabilitation of even the failed chairs on the behavior of chairs. The flexural properties of the curved specimens were firstly determined using the ASTM D143-94 test. Then, three layouts of chairs (A, B, and C) made from poplar wood were examined under the DIN EN-1729-1&2 standard. Finally, the failed chairs were rehabilitated using the sheets of glass fiber-reinforcing polymers (GFRP) and re-tested. The results showed that the rehabilitation of the curved samples causes rebounding of their mechanical properties. Besides, the rehabilitated samples are more flexible than primary ones. Furthermore, the results demonstrate that the capability of the proposed normalized modulus of rupture (NMOR) criterion, in contrast to the current modulus of rupture (MOR) one, for predicting the failure modes and regions of the wooden and composite structures. The experiments on the chairs showed that all rehabilitated patterns are more robust than primary schemes. That means, the discarded (or discarding) chairs (due to failure of joints, legs, or, in general, a part of the chairs) return to their service life, and massively reduce the demand for wood, which is strongly favored by environmental aspects. Moreover, rehabilitated layout B (RB), which has two continuous-main-curved members is at least 2.4 times stronger than other rehabilitated patterns, and rehabilitated layout C (RC) having three continuous-main-curved members is about 40% stronger than a rehabilitated custom chair (RA), that illustrates more integrity and strength. Besides that, the strength of RB is 2.22 and 2.04 times that of the corresponding primary chairs, depending on front-to-back and up-to-down loading, respectively. Finally, univariate analyses of variance and least significant difference (LSD) showed the high precision of the results. Consequently, the research provides a facility not only to save original material resources, but also to eliminate furniture waste going in the landfill.