The Research On Fundamental Properties And Toughening Modification Of Plectocomia Kerrana

Rattan is regarded as the important non-wood forestry products and has higher economicvalue. Nearly95%of rattan resources are imported from abroad. In recent years, due to theoriginal rattan export ban restrictions, shortage of raw materials has become the key issuesconstraining the development of Chinanese rattan industry. Meanwhile, the life of rattanproducts is shortened largely by brittle ruptures always caused by climate change and externalforces. How to prevent the rattan products from brittle ruptures, how to keep its highertoughness and how to enlarge its application extent has become an urgent problem to besolved.In the present work, the fundamental properties of Plectocomia kerrana Becc, a largediameter non-commercial rattan species, was thoroughly investigated, including (1)Investigating the anatomical structure, physical properties and chemical compositions;(2)Exploring the testing methods of fracture toughness based on linear elastic fracture mechanics;(3) Using methyl methacrylate (MMA) and glycidyl methacrylate (GMA) as modifier to treatthe original rattan by pressure impregnation method;(4) Comparing the fracture plane beforeand after modification by stereomicroscope and scanning electron microscope as well asexploring the possible fracture mechanisms;(5) Comprehensively evaluating the mechanicalproperties of modified products and discussing its applicability as raw materials for frameworkof rattan furniture;(6) Providing basic database for the research area of rattan mechanicalperformance and feasible plan for optimizing inferior rattan.The main conclusions are as follows:(1) Plectocomia kerrana Becc is a gradient material with large differences in the nature ofcore and cortex. Vascular bundles (Vbs) arrange tightly in cortex and sparsely in core, whichonly contain a phloem and a protoxylem vessel. The dimension of Vbs decrease from cortex tocore direction, while its distribution density increases along with the rattan altitude. The basic density of rattan is0.2746g/cm3. The microfibril angle is31.05°and the relative crystallinity is23.47%. The bending strength and bending modulus is31.05Mpa and1.04Gpa, while thecompressive strength and the compressive modulus is17.87Mpa and831Mpa, respectively.The holocellulose content ranges from66.51%~72.96%, while the lignin content ranges from16.73%~22.03%.(2) The crack prefabricated from core is determined by the stress intensity factor K, whilethe crack prefabricated from cortex is determined by energy release rate G. The value ofnominal fracture toughness is0.476MPa·m1/2and0.263MPa·m1/2, respectively.(3) The modification effect proves to be obvious when treated with MMA and GMA. Theoptimized modification process is A1B1C2D2, that is, impregnation concentration100%MMA,atmospheric pressure, curing temperature60℃, impregnation time4h. For the modifiedproducts, the bending modulus, the bending strength, the compressive modulus, compressivestrength and fracture toughness increases by127%,200%,146%,119%and231%,respectively.(4) When the rattan is bended, the crack in the rattan extends along with the crack planeprefabricated. Within the parenchymatic tissue, the crack extends transversely and changes itsdirection when the crack stretches into fiber sheath. The crack edge shows a ladder type. Afterimpregnating with modifier, the fracture route of rattan changes. The crack stretches along withthe direction of crack prefabricated. The crack edge displays a linear type. Moreover, thereexists a positive linear correlation between fracture toughness and Vbs distribution density.