Papers by Author: Zhi Yong Cai

Abstract: This research evaluated the planing performance of bamboo scrimber boards at three feed speeds and three cutting depths and used two methods to assess the finished surfaces. A macroscopic grade assessment was made according to ASTM D 1666-87 for visible planing defects. The other assessment was a microscopic scale roughness test measuring surface average roughness in terms of GB/T 12472. The visible results showed that the finished surface quality of bamboo resulted mainly in Grades and , with the main defect being torn grain. The two evaluations method showed consistent results in surface quality that the highest percentage of Grade was counted and the lowest roughness value occurred. Compared with the hardwood Sawtooth oak widely used in furniture industry in China, planning quality of bamboo scrimber board is better in terms of roughness.

Abstract: Microwave treatment is a newly developed technique to expel resin from pine wood by generating high internal steam pressure. To understand the mechanism of deresination process during the treatment, a mathematical model was developed and was used to predict its critical conditions. The model indicated that the critical pressure inside Masson pine wood was 1.17×10⁵ Pa and its corresponding critical temperature was 104 °C in order to expel the resin mixture from the interior to the surfaces. The experiment results showed that during microwave deresination large quantities of the resin overflowed to the wood surfaces when the temperature of the pine wood was controlled in the range 104-112°C. The result observed during the microwave treatment matched well with the critical temperature predicted from the simple mathematical model. The validated model could provide some understanding and improvement of microwave deresination process.

Abstract: Radiations from different electrical devices cause electromagnetic interference which will influence the performance realization of other electromagnetic device and cause the health concerns. The aluminum plates were then used to develop wood electromagnetic shielding composites by laminating with the plywood. Their static modulus of elasticity and electromagnetic shielding effectiveness of the composites with different thickness and position of aluminum plates were evaluated. The results showed that the strength of composites were improved by laminating the aluminum plates on the surface. The electromagnetic shielding performance of the composites were increased by the design of the multilayer and sandwich shielding structure. Again, It was also found that the composites made by laminating two aluminum plates (1mm, in the middle or on the surface) had a better shielding effectiveness (60 dB to 92 dB, 60 dB to 106 dB, Ranged from 1 GHz to 10 GHz) and met the requirement for a commercial electromagnetic shielding building product.

Abstract: In this study the effect of heat treatment on some physical properties of Douglas fir (Pseudotsuga menziesii) was investigated. Wood specimens were subjected to heat treatment at 160, 180, 200 and 220°C for 1, 2, 3 and 4h. The results show that heat treatment resulted in a darkened color, decreased moisture performance and increased dimensional stability of wood. Compared with untreated wood, equilibrium moisture content (EMC), water absorption (WA) and volume swelling (VS) for treated wood decrease up to 42.63%, 34.93% and 67.47%. The higher the treatment temperature and the longer the treatment time, the lower EMC, WA and VS. The VS of treated specimens has a more significant reduction than EMC and WA when the heat treatment temperature is above 180°C. The visual color changes were more distinct after heat treatment above 180°C. Temperature has a greater influence than time on these properties of specimens.