| There are abundant bamboo resources in China. Exploration and utilization of bamboo resources can help to alleviate the severe shortage of timber resources. The large variation of bamboo properties is determined by the structure characteristics of bamboo, but it is unfavorable for engineered bamboo products, which properties are uniform, and stable.Grading is a primary necessary procedure of utilization of bamboo. A scientific manufacture method should be designed for engineered bamboo products.The thesis started from the large variation of bamboo properties, then dimension bamboo strips after grading according to their densities, were processed into glued bamboo laminates with different densities and the mechanical properties of glued bamboo laminates were evaluated. The adhesion properties of epoxy resin(EP), phenol-resorcinol-formaldehyde adhesive(PRF) and phenol-formaldehyde adhesive(PF) were studied and the distribution of stress and strain on bonding interface were investigated by application of adhesive bonding stress model. The influence of temperature and water on the adhesion properties were also studied. The glued bamboo laminates from different density grades were used to design and manufacture the glued laminated bamboo and the bending properties of glued laminated bamboo were also investigated. The main conclusion of this thesis is listed following:(1) The density and bending properties of dimension bamboo strips varied wide and the correlation between density and bending properties were good, so density grading of dimension bamboo strips is necessary. There is significant mechanical properties difference between the glued bamboo laminates from different density grades, which is beneficial to the use efficiency of glued bamboo laminates.(2) The dry shear strength of PRF, PF and EP varied small, which is approximate to the shear strength of glued bamboo laminates. The wet shear strength of three adhesives were separately 4.64 MPa, 4.42 MPa and 3.7 MPa. After cover the transverse section with epoxyduring boiling, the wet shear strength of three adhesives were separately improved by 24.6%,22% and 44.9%.(3) The experiment research on bending with different spans showed that the average modulus of elasticity of EP155, EP277 and EP219 were separately 2921 MPa, 2231 MPa and3083 MPa, and the corresponding shear modulus were 359.37 MPa, 281 MPa and 454 MPa.The difference between EP155 and EP244 implied that the toughening agent CYH-277 improved the toughness of epoxy resin.(4) The stress and strain distribution of joint interface were studied by model calculation and digital image correlation analysis method. The load dispersed at all field in early state and all the distribution centralized near the bonding interface. This research validated the appliance and accuracy of the Volkersen’s model applying to the adhesion of glued bamboo laminates and this made a foundation for joint design of glued bamboo laminates.(5) The dynamic mechanical properties of bamboo and its bonded specimen were investigated by DMA method. With the temperature increase, the storage modulus(E?)decreased and Tanδ increased. Only a peak at 140℃ due to the glass transition of lignin was checked out among PF and PRF, but the glass transition appeared at 100℃. This implied that thermostabilization of PF and PRF was better than EP.(6) TGA analysis was applied to study the thermal stability of bamboo and its bonded specimen, and the kinetic pyrolysis parameters was calculated. The thermal degradation was slow until 200℃,and it accelerated after 200℃. A degradation peak appeared at 350℃. The degradation finished at 400 ℃ with the residue of 18%. The highest degradation speed of bamboo was faster than its bonded specimen and it suggested that the adhesion interface was good. The active energy of bamboo was 135.9 k J·mol-1~154.0 k J·mol-1(R2= 0.9628~0.9870),The active energy of EP and PRF was separately 147.25 k J·mol-1~188.18 k J·mol-1 and128.2298 k J·mol-1~151.0279 k J·mol-1.(7) The water transform was mainly along longitudinal direction, and the migration rate of water was larger in longitudinal direction than that in radial and tangential direction. The shrinkage coefficient in radial direction was smaller than that in tangential direction. The shearstrength of EP reduced with the water content state of glued bamboo laminates transformed from absolute dry to air dry, but it declined little when the water content state of glued bamboo laminates transformed from air dry to saturation. The shear strength of PRF decreased with the water content state of glued bamboo laminates transformed from absolute dry to saturation.These suggested that PRF was more vulnerable to the change of water content in glued bamboo laminates than EP.(8) Glued laminated bamboo of Type A and Type B was designed and manufactured according to the methods in glulam design. The MOR of Type A and Type B were respectively87.13 MPa and 82.16 MPa, the corresponding MOE were 13300 MPa and 16000 MPa. The typical failure in bending of glued laminated bamboo was the destroy of the laminate in tension.The mathematical calculation methods were compatible and the error of bending stiffness and strength were separately 7.6% and 23.0%. |
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