Continuous ultrasonic welding of thermoplastic composites: Enhancing the weld uniformity by changing the energy director

Jongbloed, B.C.P.; Teuwen, Julie J.E.; Palardy, Geneviève; Villegas, Irene Fernández; Benedictus, Rinze

doi:10.1177/0021998319890405

Cited by 38 publications

(26 citation statements)

References 16 publications

(39 reference statements)

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“…Triangular protrusions are typically employed in the plastics industry, but for continuous fiber-reinforced thermoplastics, thin films are also suitable and lead to high strength welds [ 14 , 15 , 16 , 17 , 18 ]. Many studies in the literature experimentally investigated the effect of process parameters (amplitude, force and control mode) and ED geometry on bond quality [ 10 , 14 , 15 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ] and heat generation [ 18 , 27 , 28 ]. For instance, it was reported that using the vertical displacement of the sonotrode could lead to consistent weld quality using power and displacement curves from the welder.…”

Section: Introductionmentioning

confidence: 99%

Disassembly Study of Ultrasonically Welded Thermoplastic Composite Joints via Resistance Heating

Frederick

Palardy

2021

Materials

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This manuscript explores the disassembly potential of ultrasonically welded thermoplastic composite joints for reuse or recycling through resistance heating via a nanocomposite film located at the welded interface. Nanocomposite films containing multi-walled carbon nanotubes (MWCNTs) were characterized for thermo-electrical behavior to assess self-heating. It was generally observed that maximum temperature increased with MWCNT and film thickness. To demonstrate potential for disassembly, glass fiber/polypropylene adherends were welded with nanocomposite films. Shear stress during disassembly was measured for three initial adherend’s surface temperatures. It was found that the required tensile load decreased by over 90% at the highest temperatures, effectively demonstrating the potential for disassembly via electrically conductive films. Fracture surfaces suggested that disassembly was facilitated through a combination of nanocomposite and matrix melting and weakened fiber–matrix interface. Limitations, such as slow heating rates and the loss of contact at the interface, imply that the method could be more suited for recycling, instead of repair and reuse, as the heat-affected zone extended through the adherends’ thickness at the overlap during heating.

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Section: Introductionmentioning

confidence: 99%

Disassembly Study of Ultrasonically Welded Thermoplastic Composite Joints via Resistance Heating

Frederick

Palardy

2021

Materials

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“…Heat generation is focused at the weld interface by means of an energy director (ED) placed in between the adherends [17,19]. This ED consists of either one or more resin protrusions moulded on the surface of one of the adherends [20][21][22] or a loose resin-rich layer such as a film (also referred to as flat ED) [19,23] or a woven mesh [14,24] made from the same polymer material as that in the adherends. Due to the lower compressive stiffness of the ED compared to that of the fibre reinforced adherends, the ED undergoes higher cyclic strains and it therefore generates more heat than the adherends [22,25].…”

Section: Introductionmentioning

confidence: 99%

“…Sequential application of this static process allows obtaining multi-spot welded joints that can match load carrying capabilities of mechanically fastened joints [26,27]. The continuous ultrasonic welding process (Figure 1b) is defined as follows: a relatively large area is welded by continuously translating the welder with respect to the adherends or vice versa while exerting the ultrasonic vibrations and welding pressure [14,24]. Since the sonotrode continuously moves away from the just welded area, an additional consolidation shoe (consolidator) needs to be placed behind the sonotrode to allow the weld to cool down under pressure [15].…”

Section: Introductionmentioning

confidence: 99%

A Study on Through-the-Thickness Heating in Continuous Ultrasonic Welding of Thermoplastic Composites

et al. 2021

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Continuous ultrasonic welding is a promising technique for joining thermoplastic composites structures together. The aim of this study was to gain further insight into what causes higher through-the-thickness heating in continuous ultrasonic welding of thermoplastic composites as compared to the static process. Thermocouples were used to measure temperature evolutions at the welding interface and within the adherends. To understand the mechanisms causing the observed temperature behaviours, the results were compared to temperature measurements from an equivalent static welding process and to the predictions from a simplified heat transfer model. Despite the significantly higher temperatures measured at the welding interface for the continuous process, viscoelastic bulk heat generation and not thermal conduction from the interface was identified as the main cause of higher through-the-thickness heating in the top adherend. Interestingly the top adherend seemed to absorb most of the vibrational energy in the continuous process as opposed to a more balanced energy share between the top and bottom adherend in the static process. Finally, the higher temperatures at the welding interface in continuous ultrasonic welding were attributed to pre-heating of the energy director due to the vibrations being transmitted downstream of the sonotrode, to reduced squeeze-flow of energy director due to the larger adherend size, and to heat flux originating downstream as the welding process continues.

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“…double cantilever beam test coupons, relatively complex experimental set-ups need to be built in which an end effector with heating and pressure application capabilities is automatically translated along the area to be welded [14–16]. Furthermore, the addition of this extra degree of freedom requires, on some occasions, a substantial redefinition of the basic aspects of the welding process itself [17,18].…”

Section: Introductionmentioning

confidence: 99%

The dangers of single-lap shear testing in understanding polymer composite welded joints

Villegas

Rans

2021

Phil. Trans. R. Soc. A.

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Single-lap shear (SLS) joints are straightforward to manufacture. This makes them especially attractive for testing polymer composite welded joints. Owing to local heating, which is characteristic of composite welding processes, the production of more geometrically intricate joints (such as double-lap or scarfed joints) or bigger joints (such as end-notched flexure or double cantilever beam) typically entails significant complexity in the design of the welding process. Testing of SLS joints is also uncomplicated and, even though, owing to mixed-mode loading and uneven stress distribution, it does not provide design values, it is widely acknowledged as a valuable tool for comparison. Even so, comparing different aspects of composite welded joints through their corresponding SLS strength values alone can be deceptive. This paper shows that comparison of different welding processes, adherend materials, process parameters or different types of joining techniques through SLS testing is only meaningful when strength values are combined with knowledge on other aspects of the joints such as joint mesostructure, failure modes and joint mechanics. This article is part of a discussion meeting issue ‘A cracking approach to inventing new tough materials: fracture stranger than friction’.

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Continuous ultrasonic welding of thermoplastic composites: Enhancing the weld uniformity by changing the energy director

Cited by 38 publications

References 16 publications

Disassembly Study of Ultrasonically Welded Thermoplastic Composite Joints via Resistance Heating

Disassembly Study of Ultrasonically Welded Thermoplastic Composite Joints via Resistance Heating

A Study on Through-the-Thickness Heating in Continuous Ultrasonic Welding of Thermoplastic Composites

The dangers of single-lap shear testing in understanding polymer composite welded joints

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