Investigating the Effects of Forming Parameters on Molding Force and Springback in Deep Drawing Process of Thermoplastic Composite Laminates

Abstract

The automotive industry and research centers have intensified the search for innovative solutions in the field of material technologies and have recently accelerated their work on thermoplastic based composites in line with their requirements. Thermoform method is used for rapid forming of thermoplastics and composites. In this process, mold design and especially molding parameters are important for part quality. Thermoplastic composite sheets take the shape of their final form by spring back after they come out of the mold as in sheet metals. Therefore, springback is a parameter that should be taken into account in the manufacturing process and product design. In this study, preliminary research was carried out to design the forming process in thermoform mold. The experiments were done on Nakajima test setup and according to ISO 12004 standard. In the deep drawing of thermoplastic composite laminates, the effects of different holding pressure (0.4; 0.6; 0.8 MPa), punch speed (90, 120, 150 mm/min), specimen temperature (129, 159, 169 oC) and piece depth (20, 25, 30 mm) parameters on the molding force were examined and the spring back amount of deep drawn specimens was determined. As a result of the experiments, as the specimen temperature increased the molding force decreased. The molding force increased as the holding pressure increased. Increasing punch speed caused an increase in required molding force. As a result of the experiments, it was concluded that deep drawing can be made up to a depth of 25 mm.

Keywords

• Deep drawing
• Springback
• Molding force
• Forming
• Thermoplastic composite laminate

References

1. [1] Kim, D.W., Kim, Y.S., Jung, YC, Kim, S.Y., Song, J.M., Kim, M., and Kim, J., "Development of a continuous manufacturing process for self-reinforced composites using multi-step highly drawn polypropylene tapes". Polymer, 191: 122267, (2020).
2. [2] Lu, K., "The future of metals", Science, 328(5976): 319-320, (2010).
3. [3] Yan, L., Chouw, N., Jayaraman, K., "Flax Fibre and its composites – A review", Composites Part B: Engineering, 56: 296-317, (2014).
4. [4] Yao, S.-S., Jin, F.-L., Rhee, K.Y., Hui, D., Park, S.-J., "Recent Advances in carbon-fiber-reinforced thermoplastic composites: A review", Composites Part B: Engineering, 142: 241-250, (2018).
5. [5] Conte, R., Ambrogio, G., Pulice, D., Gagliardi, F., Filice, L., "Incremental sheet forming of a composite made of thermoplastic matrix and glass-fiber reinforcement", Procedia Engineering, 207: 819-824, (2017).
6. [6] Morrow, C., Dhar, M.S, Venkatesan, S., Kalyanasundaram, S., "Stretch forming studies on thermoplastic composite", Paper presented at the 6th Australiasian Congress on Applied Mechanics, Perth, Australia (2010).
7. [7] Vyas, S., Goli, E., Zhang, X., Geubelle, P.H., "Manufacturing of unidirectional glass-fiber-reinforced composites via frontal polymerization: A numerical study", Composites Science and Technology, 184: 107832, (2019).
8. [8] Bhattacharyya, D., Bowis, M., Jayaraman, K., "Thermoforming woodfibre–polypropylene composite sheets", Composites Science and Technology, 63 (3): 353-365, (2003).

9. [9] Alcock, B., Cabrera, N.O., Barkoula, N.M., Peijs, T.,"Direct forming of all-polypropylene composites products from fabrics made of co-extruded tapes". Applied Composite Materials, 16 (2): 117-134, (2009).
10. [10] Cabrera, N.O., Reynolds, C.T., Alcock, B., Peijs, T., 2008, “Non-isothermal stamp forming of continuous tape reinforced all-polypropylene composite sheet", Composites Part A: Applied Science and Manufacturing, 39 (9): 1455-1466, (2008).
11. [11] Lee, J.H., Vogel, J.H., Rhee, K.Y., "An Analysis of Stretch Forming of Thermoplastic Composites", Polymer Composites, 23 (3): 442-453, (2002).
12. [12] Labeas, G.N., Watiti, V.B., Katsiropoulos, C.V., 2008, "Thermomechanical Simulation of Infrared Heating Diaphragm Forming Process for Thermoplastic Parts", Journal of Thermoplastic Composite Materials, 21(4): 353-370, (2008).
13. [13] The British Standards Institution, Metallic materials. Sheet and strip. Determination of forming-limit curves. BS EN ISO 12004 (2020).
14. [14] Panich, S. Liewald, M., and Uthaisangsuk, V.,"Stress and strain based fracture forming limit curves for advanced high strength steel sheet", International Journal of Material Forming, 11, pp. 643-661, (2018).