High Toughness And Super Elastic Property Of Epidermis Tissue With Its Macro & Micro-structure In Stems Of Foxtail Millet

With their high strength and toughness,stems of foxtail millets usually not easy be broken under the tensile load.Entangled with each other,the stem-twining often take place between foxtail millet and reelorgrainlifterof millet harvester.To study the super mechanical properties of stalks of foxtail millets,three varieties of foxtail millets,Jingu 21,Zhangza 10 and Qinhuang 2,were chose to test in different internodes.And tensile tests were performed in stalks,epidermis tissue and element fibers,respectively.With the test result,the macro & micro-mechanical properties such as elastic modulus,tensile strength,failure load and the cost work are compared in different internode location and three species.The main work and conclusion are as follows:1)Tensile tests on epidermis tissue of stemWith tensile tests on the epidermal tissues from different species(Jingu 21,Zhangza 10 and Qinhuang2),the elastic moduli at different internode position(top,middle and bottom)were measured,respectively.For Jingu 21,it’s found thatthe mean elastic modulus at the middle position(4 and 6 internode)is 5.32 GPa,which is more stiffer than the bottom part(1 and 2 internode)(~4.62GPa).And the elastic modulus at the top position(8 and 10 internode)(~4.57GPa)is smaller than the other two position.For Zhangza 10,the elastic modulus(~4.83GPa)is close to Jingu 21.Whilefor Qinhuang 2,it’smore flexible than Jingu 21 and Zhangza 10(~4.28GP).The tensile strength of epidermis from Jingu 21 is ranged from 70.82(top position)to 99.45MPa(bottom position).With an average value of 99.92 MPa,the tensile strength of Zhangza 10 ranges from83.47 MPa to 116.74 MPa,which is more stronger than Jingu 21.Among these 3 species,the Qinhuang 2 is the strongest one(104.59MPa).For the failureload,Jingu 21 is varied from 54.43 to 74.19N;and Zhangza 10 ranges from 45.97 to59.17N;Qinhuang 2 changes from 52.66 N to 108.05 N.All of them decreased with the height.The energy cost for Jingu 21,Zhangza 10 and Qinhuang 2 are 0.010 J,0.008 J and 0.016 J,respectively.All of them increased with the height.2)The difficulty of fiber separation can be solved by ultrasonic treatment.Focusing on the three factors(power,temperature andtime),through single factor test combinedwith the response surface method,the influence factors on the fiber of epidermis were as follows: power>temperature>time.The optimum process parameters for ultrasonic separation of fiber were obtained as: power 350 W,time 15min,temperature 40℃.3)Tensile testson fiber of epidermis tissue :For the elastic modulus,Jingu 21 is ranged from 3.67 to 17.66 GPa,the different internode position is flexible.Zhangza 10 is the strongest at the bottom position(~12.66GPa),the weaker at the middle position(~6.54GPa),and the smallest at the top position(~4.89GPa),which is smaller than Jingu 21.Qinhuang 2 is stronger in the bottom,the strongest in the middle and the smallest in the top.The elastic modulusis varied from 5.03 to 22.82 GPa,which is different from Jingu 21 and Zhangza 10.The tensile strength of Jingu 21 is 1172.49 MPa,and Zhangza 10 changes from 467.76 MPa to1521.3MPa,the bottom position is stronger and the top position is weaker.The tensile strength of Qinhuang2 is 1221.31 MPa at the bottom position,which is more stiffer than the middle(~732.39MPa),while the top is the smallest(~587.31MPa).For the failureload,The value of maximum and minimum of Jingu 21 are 220.23 m N(bottom position)and 51.34 m N(top position),Zhangza 10 is varied from 55.14~179.21 m N.The change of failureload of Qinhuang 2 is the same as Jingu 21 and Zhangza 10.