PSI - Issue 50

S.V. Panin et al. / Procedia Structural Integrity 50 (2023) 220–227 S.V. Panin et al. / Structural Integrity Procedia 00 (2023) 000 – 000

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films and the prepreg (Fig. 3, i). The sample fractured through the base material (Fig. 1, a; curve No. 59). According to the cross-section micrograph, the prepreg lost its integrity locally. 4. Conclusions In the shear tests, fracture of the lap welded joints through the base material was associated not only with high shear stresses, but also with double macrobending of the samples because of the increased rigidity of their central parts, possessing twice thickness values. Fracture of carbon fibers due to the prepreg melting was a negative factor. However, it could provide additional reinforcement of the material in the fusion zone upon the USW process, increasing shear strength. The porosity formation at the interface could be associated with melting of both ED films and the prepreg, in addition to the joined plates from the PEEK-based composite. The prepreg melting inevitably resulted in fracture of reinforcing fibers. According to the Taguchi optimization results, the most improved functional properties were provided by Mode No. 9 (Pcompress=3 atm, τUSW=1200 ms), which corresponded to the maximum both shear strength and elongation to break values. However, the prepreg was melted and fibers fractured in this case. Taking into account the structural investigation results, Mode No. 2 was the most rational (Pcompress=3 atm, τUSW=800 ms). At the same time, both ED films were melted and the high values provided, because the welded joints fractured through the base material but the prepreg retained its integrity. It is proposed to use changes in thicknesses of the lap welded joints as one of the key parameters for controlling the USW process. For the studied combinations, it should be completed as soon as they decrease by about 350 – 400 µm, which is 100 – 150 µm less than the total thickness of both ED films. Acknowledgements The study was supported by the Russian Science Foundation, grant No. 21-19-00741. References Yan, J.C., Wang, X.L., Li, R.Q., Xu, H.B, Yang, S.Q., 2007. The Effects of Energy Director Shape on Temperature Field during Ultrasonic Welding of Thermoplastic Composites. Key Engineering Materials 353 – 358, 2007 – 2010. https://doi.org/10.4028/www.scientific.net/KEM.353-358.2007. Harras, B., Cole, K. C., Vu-Khanh, T., 1996. Optimization of the Ultrasonic Welding of PEEK-Carbon Composites. Journal of Reinforced Plastics and Composites 15(2), 174 – 182. https://doi.org/10.1177/073168449601500203. Liu, S.J., Chang, I.T., Hung, S.W., 2001. Factors affecting the joint strength of ultrasonically welded polypropylene composites. Polymer Composites 22(1), 132 – 141. https://doi.org/10.1002/pc.10525. Ramarathnam, G., North, T.H., Woodhams, R.T., 1992. Ultrasonic welding using tie-layer materials. part II: Factors affecting the lap-shear strength of ultrasonic welds. Polymer Engineering and Science 32(9), 612 – 619. https://doi.org/10.1002/pen.760320907. Tateishi, N., North, T.H., Woodhams, R.T., 1992. Ultrasonic welding using tie-layer materials. part I: Analysis of process operation. Polymer Engineering and Science 32(9), 600 – 611. https://doi.org/10.1002/pen.760320906. Jongbloed, B.C.P., Teuwen, J.J.E., Palardy, G., Villegas, I.F., Benedictus, R., 2018. Improving weld uniformity in continuous ultrasonic welding of thermoplastic composites, Proceedings of the 18th European Conference on Composite Materials: 24-28th June 2018, Athens, Greece. pp. 1-9. http://resolver.tudelft.nl/uuid:22b7283a-71c1-4fdf-80db-1008ac98c076. Villegas, I.F., Rubio, P.V., 2015. On avoiding thermal degradation during welding of high-performance thermoplastic composites to thermoset composites. Composites Part A: Applied Science and Manufacturing 77, 172 – 180. https://doi.org/10.1016/j.compositesa.2015.07.002. Gallego- Juárez , J.A., Graff, K.F., 2015. Power Ultrasonics, J.A. Gallego- Juárez, K.F. Graff, 1st Edition. – Woodhead Publishing. – 1142 p. https://doi.org/10.1016/C2013-0-16435-5. Sackmann, J., Burlage, K., Gerhardy, C., Memering, B., Liao, S., Schomburg, W.K., 2015. Review on ultrasonic fabrication of polymer micro devices. Ultrasonics 56, 189 – 200. https://doi.org/10.1016/j.ultras.2014.08.007. Sánchez - Sánchez , X., Hernández -Avila, M., Elizalde, L.E., Martínez , O., Ferrer, I., Elías - Zuñiga , A., 2017. Micro injection molding processing of UHMWPE using ultrasonic vibration energy. Materials & Design 132, 1 – 12. https://doi.org/10.1016/j.matdes.2017.06.055. Sun, Y., Liu, X., Yang, X., 2018. A novel ultrasonic precise bonding with non-constant amplitude control for thermalplastic polymer MEMS // Ultrasonics 84, 404 – 410. https://doi.org/10.1016/j.ultras.2017.12.005. VICTREX PEEK injection molding processing guide [Electronic resource]. - 2018. Access mode: https://www.victrex.com/en/technical-guides / (date of the application: 20.01.2022).