PSI - Issue 27

Sakuri Sakuri et al. / Procedia Structural Integrity 27 (2020) 85–92 Sakuri et al. / Structural Integrity Procedia 00 (2020) 000 – 000

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Increased shear strength of the interface in the treatment causes two effects on the fiber, i.e., increasing the level of surface roughness in the fiber (which will increase the interlock between the fiber and the matrix on the composite), and increasing the exposure of hydroxyl groups on the surface of the fiber. Therefore, the reactive group will easily form bonds chemistry in the presence of other compounds (Li et al., 2007). 3.4. Flexural strength Flexural strength testing using Universal Testing Machine (UTM) SANS Products co. Ltd. with the series 4160 (Laboratory of Mechanical Engineering, Universitas Sebelas Maret, Surakarta, Indonesia) with ASTM 790-03 in 2003. The results of the flexural testing are shown in Fig. 5.

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1000 1500 2000 2500 3000 3500 4000 4500 5000

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AI 6

Flexural strength ( MPa ) UE AI 3

Modulus ( MPa )

AI 9

AI 12

AI 15

Flexural Modulus

Fig. 5. Flexural and modulus test results.

The flexural test was conducted to bend the composite under the force conditions at three points. Flexural modulus was used as an indication of the rigidity of material during bending. The results show that fiber with alkali treatment can increase the flexural strength of composites. Flexural strength before treatment was 68.22 MPa, and after the alkali treatment increased by 82.32 MPa for AI 3 and with the treatment of 6 h increased to 102.34 MPa. Meanwhile, the flexural strength with 9 h soaking treatment decreased by 83.98 MPa and slightly reduced for AI 12 and AI 15 treatment, respectively 82.02 MPa and 80.32 MPa. High flexural strength was also a result of adding microcrystalline cellulose to the composite. The most upper flexural strength for kenaf and unsaturated polyester fibers with an alkali treatment of 93.40 MPa. Puvanasvaran and Sued (2011) and Kabir (2013) argued that the highest flexural strength was 31% for alkali treatment. The modulus yield increases proportionally and is similar to the flexural strength graph, which is also following sisalana fiber testing with alkaline (Jacob et al., 2014). 4. Conclusions In current market trends, natural fibers support growth and are very promising in the automotive and construction world. Recommended with the support of microcrystalline reinforcement in natural fibers, which can significantly increase the flexural strength was very promising for future material development. CF test results with surface morphology show the loss of cementing and amorphous elements such as hemicellulose, lignin, and other impurities. The surface roughness of CF increases with alkaline treatment. Fiber surface roughness increases interface adhesion between the fiber and the matrix, which were shown by increasing the IFSS results up to 3.67 MPa. Thermogravimetric analysis (TGA) test results show that CF treatment has improved thermal stability compared to the untreated specimen. The highest thermal stability at AI treatment 6 to 492 °C. The results of testing the flexural strength and modulus of