OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 3 2023 discovered with 4 % NaOH during 1 hour. Compared to other results, the results with an hourly soaking in 4 % alkali are noticeably better. It may be caused by an increase in cellulose content and the maximum possible adhesion between the fiber and matrix. Flexural strength and modulus variation are not very different for the other three situations. The increase in flexural strength and elastic modulus of layered samples without preliminary surface treatment is about 10.40 % and 32.24 %, respectively. Therefore, it may be said that surface treatment greatly enhances flexural qualities. It can be clearly seen that – the highest value of flexural strength for basket-weaved CM is 95 ± 1.17 MPa when treated with 4 % alkali solution for 1 hour, and its flexural modulus is 3.99 ± 0.23 GPa; – the second highest value of flexural strength for basket-weaved CM is 71.7 ± 0.60 MPa with treatment with 1 % alkali solution for 1 hour, and its flexural modulus is 3.2 ± 0.10 GPa; – the lowest value of flexural strength for basket-weaved CM is 70.6 ± 0.20 MPa upon treatment with 1 % alkali solution for 30 minutes, and its flexural modulus is 2.6 ± 0.11 GPa; – the second and last lowest flexural strength for basket-weaved CM is 70 ± 0.60 MPa when treated with 4 % alkali solution for 30 minutes, and its flexural modulus is 2.8 ± 0.18 GPa. Impact Test Impact test was carried out on a woven jute composite to investigate impact energy* and result is shown in Table 4. Ta b l e 4 Impact test of woven jute composite Number of layers Pattern & time with NaOH Concentration Impact energy, J/m 4 Basket (30 minutes, 1 %) 272 ± 23 Basket (1 hour, 1 %) 274 ± 24 Basket (30 minutes, 4 %) 278 ± 25 Basket (1 hour, 4 %) 280 ± 26 Number of layers Pattern & time with NaOH Concentration Impact energy, J/m 4 Basket 250 ± 26 The test results indicate the ability of the material to store energy when loaded. According to Table 4, the impact energy of the composite increased significantly after surface treatment by about 10 %. It is clearly seen that – the highest impact energy for basket-weaved CM is 280 ± 26 J/m when treated with 4 % alkali solution for 1 hour; – the second highest impact energy for basket-weaved CM is 278 ± 25 J/m with treatment with 1 % alkali solution for 1 hour; – the lowest impact energy for basket-weaved CM is 274 ± 24 J/m upon treatment with 1 % alkali solution for 30 minutes; – the second and last lowest impact energy for basket-weaved CM is 272 ± 23 J/m when treated with 4 % alkali solution for 30 minutes. * The ASTM impact energy is measured in J/m or ft-lb/in. Impact strength results from dividing the value for impact energy in (J or ft-lb) by the notch thickness (mm or inches) of the specimen, for an average of 5 test cycles. The ISO method is slightly different, deriving impact strength with units kJ/m2 from the impact energy in J by the area under the notch. This test is performed on 10 specimens and the results are averaged. –––––––––––––
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