Fabrication of Fiber Reinforced Plastics by Ultrasonic Welding

Abstract

Ultrasonic fabrication of fiber reinforced plastics made from thermoplastic polymer films and carbon or glass fibers enables cycle times of a few seconds and requires investment costs of only some 10,000 €. Besides this, the raw materials can be stored at room temperature. A fiber content of 33 vol % and a tensile strength of approximately 1.2 GPa have been achieved by ultrasonic welding of nine layers of foils from polyamide, each 100 µm in thickness, and eight layers of carbon fibers, each 100 µm in thickness, in between. Besides unidirectional carbon fiber reinforced polymer composite (CFRP) samples, multi-directional CFRP plates, 116 mm, 64 mm and 1.2 mm in length, width and thickness respectively, were fabricated by processing three layers of carbon fiber canvas, each 300 µm in thickness, and eight layers of polyamide foils, each 100 µm in thickness. Furthermore, both the discontinuous and the continuous ultrasonic fabrication processes are described and the results are presented in this paper. Large-scale production still needs to be demonstrated.

Integration of eddy current sensors into repair patches for fatigue reinforcement at rivet holes

“…To this end, a suitable production technique needs to be found that is able to join the ECS with the composite patch. Here, the method of ultrasonic welding is used, which was described in depth by Gomer et al [30,31] This method is advantageous as it has short cycle times and allows patch manufacturing from raw carbon fabric and polymer film. Compared to conventional base materials such as prepregs or epoxy resin, these materials are harmless to health and less demanding in terms of storage conditions [32,33] .…”

“…For the ultrasonic fabrication of CFRP, the carbon fibres are rolled off from a roving or a fabric roll, and the thermoplastic resin is given as a polymer film from polyamide 6 (PA6). Fibres and matrix are welded into a laminate by an ultrasonic welding machine in a single process, which can be broken down into five steps for easier description [31] . For the preparation of the process, fibres and matrix foil are stacked in layers (for the sake of simplicity one layer in Figure 4a).…”

“…Schematical illustration of the ultrasonic fabrication of CFRP: (a) down stroke of the horn of the ultrasonic welding machine on the stack of carbon fibres and polymer film; (b) compression of the stack; (c) melting of polymer by ultrasonic vibrations; (d) solidification of the polymer at predetermined holding force and time; (e) lift up of the horn [31] …”

“…This is followed by a piece of carbon fabric measuring 50 × 50 mm which is fixed by two further layers of PA6 film. Due to the additional interfaces, more friction is generated in a double layer of polymer film than in a single layer of twice the thickness [31] . Alternately, one layer of carbon fibre fabric and two layers of PA6 foil are applied.…”

“…Given the fact that for this proof‐of‐concept, a detailed calculation of the interaction between structure and RSP was neglected, there is optimisation potential for the dimensioning of the broad CFRP ring patch. Possible starting points are the use of unidirectional fibres and, as the ultrasonic processing of CFRP is relatively new, an enhancement of the fabrication process itself, for example, by increasing the fibre volume ration [31] . Furthermore, the repair performance of ultrasonically fabricated CFRP in comparison to CFRP from conventional production may be subject to further studies.…”