Tensile Strength of Maize Stalk and Husk single Cellulose Fiber

Maize stalk and husk fibers, as reinforcement, have recently attracted the attention of researchers because of their advantages over other established materials. They are environmentallyfriendly, fully biodegradable, abundantly available, non-toxic, non-abrasive, renewable, cheap, and have low density. Cellulose fiber extracted from maize stalk using retting process then its tensile strength and young modulus determined according to ASTM D3822. the fiber specimen were subjected to uniaxial tensile loading at a rate of 100mm/min. Form the recorded load – elongation result ,tensile stresses and young modulus were determined. The maize stalk and husk fiber image were captured by biological microscope. Cross sectional width was measured using TS view software. The results were 44μm and 73μm respectively. The measured ultimate tensile stress for maize stalk cellulose fiber treated by NaOH purity 98% for 30 minutes ranged from 625Mpa to 1478Mpa (average 1184.04Mpa), young modulus from 6728.99Mpa to 24107.94Mpa (average 16.27Gpa) and for maize husk fiber treated by NaOH the measured ultimate tensile stress ranged from 446.44Mpa to 1609.66Mpa (average 973.9Mpa), Young modulus from 3121.94Mpa to 13342..63Mpa (average 6.24Gpa). Keywordfiber, cellulose, retting, test, maize

of 1.5 g/cm 3 , average diameter of 145 µm with a range of 60-220 µm, average tensile strength and elastic modulus of 141 MPa and 6.3 GPa, respectively [11]. Moreover the maize stalk fibers were tested for tensile strength; fibers of uniform size were selected and tested in Hounsfield tensometer machine .The ultimate strength of the fibers was 152Mpa with average Young's modulus of 8582Mpa [12]. Axial tensile modulus, ultimate strength and failure strain of single fibers are determined for carbon and glass fibers. ASTM D3379-75 standard is followed and a number of fibers were tested for statistical analysis. The axial tensile moduli measured are 246.7Gpa and 93.3Gpa, respectively and strength are 3031.6Mpa and 2035.9Mpa respectively for carbon and glass fibers [14].For the tensile testing of natural fiber, the closest applicable standard used was ASTM D 3822-01 the 'Standard for Tensile Properties of Single Fibers'. This ASTM standard was typically used to quantify the mechanical properties of textile fibers and threads, which are often from a natural source, such as flax or cotton [15]. whereas the other three did not have any statistical difference. Ramie had the largest elongation at break and the lowest modulus. Elongation at break of kenaf was significantly smaller than that of the other fibers. [16].An improved Single Fiber Tensile Test (SFTT) for the natural fibers was depicted. Natural fibers have irregular shape, and are not uniform along the fiber length and also from one fiber to another. Applying the conventional method, which determine the fiber cross-section by measuring the fiber diameter using optical microscopy, will result in inaccurate properties of the natural fibers with large standard deviation (SD). In the proposed new SFTT method, an accurate cross-section area could be obtained from the Scanning Electron Microscope observation of a flat and clear fractured end surface of carefully selected tensile-tested fibers and calculated using imaging analysis. In many practical situations, the cross -sections of natural fibers are assumed to be circular and the projected width of the fiber is used to calculate a cross sectional area. Virk who suggested the use of a "fiber area correction factor" of 1.42 in the measurement of fiber modulus and strength to account for the overestimation of the fiber CSA by the diameter method. It is relatively easy to qualitatively understand this effect when considering the transverse observation of a non-circular cross section cylinder to obtain a "diameter" measurement. Indeed, in such a case the error in the estimation of the fiber CSA will increase with increasing aspect ratio of the major to minor axes of the fiber cross section, which will also result in higher values of "diameter" for fibers of equal CSA. Agricultural residue is becoming a major source of fibers in the development of composites. The abundant availability and accessibility of maize stalk fibers are the major reasons for an emerging new interest in sustainable technology.

Material and Method 2.1 Maize Stalk and Husk Fiber Extraction
Maize stalk fiber was selected based on abundance, accessibility, mechanical property, low cost. Maize stalk fiber was collected from a research plantation area at Ethiopia National Agricultural Research Institute Kulumsa branch. Water retting natural fiber extraction process used in this research work in order to gain fiber of grater uniformity and higher quality, Duration of retting process was 14 Days. Maize stalk Local Varity Harvested April, 12/2017 and Air dried for 15 days then cut in to internodes as shown on fig 1. Each node split into two pieces and immersed in to NaOH solution of 2.5g/10 L volume together with its husk as fig.2 show. After 14 days the lignin dissolved and cellulose fiber easily separated from the hemicellulose by hand then washed by water several times. The leafy outer shell/covering of an ear of maize is referred to as corn husk. Alkalization is a common pre-processing technique used on base natural fiber to remove hemicelluloses, fats and waxes that may reduce the interfacial strength when processed into composite form so the extracted cellulose fiber treated by 98%purity NaOH for 30min shown on fig.3 and fig .7.

Fiber tensile strength test
Single maize stalk cellulose fiber tensile strength test were conducted at research laboratory of Ethiopia Textile and Fashion Institute. Fiber tensile strength test of ten maize stalk single fiber and twenty maize ear husk single fiber conducted using fiber strength test machine as fig.5 shows with 10 N load cells, gauge length 25mm and speed 100mm/min was used for the tensile test of a single fiber with ASTM D3822 standard. As fig.4 shows breaking force result of ten different maize stalk cellulose fiber samples was considered. we determined average breaking force 2.49N and average elongation 2.21%.And also as fig.6 shows breaking force result of twenty different maize husk fiber samples were considered from the result we achieved average break force 5.75N and average elongation 4.2%.   The cross section of NaOH treated maize stalk fiber of 40 samples randomly at top, middle and bottom side image captured by biological microscope and its cross section measured by TSview software. As shown on fig.9 ,average diameter 44μm were taken and similarly 20 samples maize husk fiber measured and average diameter of the fiber 73μm were taken in order to determine the tensile strength of the fiber. This is in good agreement with very recent results from a study of jute fiber diameter by (Virk) who suggested the use of a" fiber area correction "factor of 1.42 in the measurement of fiber modulus and strength to account the over estimation of the fiber cross section area by the diameter method. For maize stalk single celluose fiber Cross section diameter range from 25μm to 60μm average 44 μm and for maize husk celluose fiber Cross section range from 48 μm to 90 μm average 73 μm and 1.42 cross sectional area correction factor was considered during calculation based on previous researcher as shown on fig. 10 and 11, respectively.

2.4.Tensile Strength result of maize stalk single fiber
As figure 12 shows, Breaking force result of ten different sample and cross section diameter of fiber 44μm were taken to determine the Tensile strength average 1184.04Mpa achieved. σ = F/A (eq.1) Where, σ = Tensile Strength F = Breaking force A=cross sectional area, 2.6. Young modulus result of single maize stalk fiber Young modulus determined from the relationship, σ = E ε (eq.2) ε = ϪL/L O (eq.3) Where, E = Young modulus σ = stress ε = strain ϪL = Change in length L O = Original length As figure 12 shows, Elongation result of ten different sample and gauge length of 25mm were taken to determine the strain. Young modulus = stress/strain, average 16268.5Mpa achieved.

Result and Discussion
From conducting the tensile testing of the maize stalk fibers, graphs that offer a typical representation of the properties for NaOH treated maize stalk cellulose fiber and maize husk fiber can be viewed in Fig. 12, 13 and 14. These fibers were tested at room temperature. Cellulose fiber extracted from maize stalk using retting process then its tensile strength and young modulus were determined according to ASTM D3822 the fiber specimen were subjected to uniaxial tensile loading at a rate of 1.6mm/sec. Average measured cross section diameter 44um for maize stalk fiber and 73um for maize cob husk fiber, cross sectional area correction factor 1.42 were used to determine its tensile strength and young modulus. From the recorded load -elongation result, tensile stresses modulus of elasticity were determined. The measured ultimate tensile stress for maize stalk cellulose fiber treated by NaOH purity 98% for 30 minutes ranged from 625Mpa to 1478Mpa (average 1184Mpa), young modulus from 6728.99Mpa to 24107.94Mpa (average 16.27Gpa) and for maize husk fiber treated by NaOH the measured ultimate tensile stress ranged from 446.44 Mpa to 1609.66Mpa (average 973.9Mpa), Young modulus from 3121.94Mpa to 13342.63Mpa (average 6.24Gpa). From the result, treated maize stalk cellulose fiber displays the largest average tensile stress and Young modulus then treated maize husk fiber.

Conclusion
Maize stalk and husk harvested and dried at room temperature. The stalk cut into its inter nodes then split in to two then submitted in to water solution contain 2.5g/10L then retted for 14 days at atmospheric temperature .Lignin dissolve in the solution and the cellulose fiber separated from hemicellulose using hand by pulling out. After cellulose fiber separated from the maize stalk and husk it was washed several times then dried. The extracted maize stalk and husk fiber treated by Chemical NaOH purity 98% for 30 minutes. Then tensile testing carried out based on ASTM D 3822 standard. From the result, it is possible to use as reinforcement for development geopolymer composite.