Optimizing the joint strength of ultrasonically welded thermoplastics

Liu, Shih‐Jung; Lin, Wen-Fei; Chang, Bo-Chien; Wu, G.M.; Hung, Shiu-Wan

doi:10.1002/(sici)1098-2329(199922)18:2<125::aid-adv3>3.0.co;2-a

Cited by 37 publications

(15 citation statements)

References 13 publications

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“…Typically, EDs are shaped like triangular, semi-circular or rectangular protrusions. [7][8][9][10][11][12][13] However, a simpler shape, so-called 'flat energy directors' , made of a neat polymer CONTACT Genevieve palardy g.palardy@tudelft.nl…”

Section: Introductionmentioning

confidence: 99%

On the effect of flat energy directors thickness on heat generation during ultrasonic welding of thermoplastic composites

Palardy

Villegas

2016

Composite Interfaces

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This paper presents a detailed experimental assessment of the effect of the thickness of flat energy directors (ED) on heat generation at the interface during ultrasonic welding. Power and displacement data showed clear differences caused by the change of thickness, related to heat concentration at the weld line during the process. The extent of the heat-affected zone was assessed by welding specimens without consolidation at different stages of the process. It was confirmed through optical microscopy that heat is generated at the interface and transferred to the bulk adherends earlier in the process for thinner ED. The analysis of their fracture surface under optimum welding conditions revealed signs of matrix degradation, leading to less consistent quality, likely due to faster heat generation rate in both the ED and the substrates, and incidentally, higher temperatures surrounding the energy director.

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Section: Introductionmentioning

confidence: 99%

On the effect of flat energy directors thickness on heat generation during ultrasonic welding of thermoplastic composites

Palardy

Villegas

2016

Composite Interfaces

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“…Semi-crystalline polymers such as HDPE, PP, PE, and polyester are generally difficult to weld ultrasonically due to the greater energy required to melt crystals and initiate intermolecular diffusion, and they are particularly difficult in the far-field configuration, due to damping. Liu et al ultrasonically welded amorphous polystyrene (PS) and semicrystalline PP [80]. They found that weld time and amplitude of vibration were significant parameters affecting weld strength.…”

Section: Friction Weldingmentioning

confidence: 99%

Welding methods for joining thermoplastic polymers for the hermetic enclosure of medical devices

Amanat¹,

James²,

McKenzie³

2010

Medical Engineering & Physics

171

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“…They modeled the viscoelastic heating of the ED assuming adiabatic heating and used elastic analysis to estimate the strain amplitude within parts. Liu et al 10 carried out optimizing studies of the joint strength of ultrasonically welded joints using statistical methods. The results of their study indicate that the weld time and the amplitude of vibration were the principal factors affecting the strength of the joint.…”

Section: Literature Reviewmentioning

confidence: 99%

Study of Different Joints for Ultrasonic Welding of Semicrystalline Polymers

Rani¹,

Prakasan²,

Rudramoorthy³

2009

Experimental Techniques

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U ltrasonic welding (USW) uses vibratory energy at high frequencies that are beyond the range of human hearing to produce low amplitude (20-30 mm) mechanical vibrations. The vibrations generate heat at the interface of the parts being welded, resulting in melting of the thermoplastic materials and weld formation after cooling. Figure 1 shows the schematic of the USW process.There are two basic types of joints practiced by the industry for USW of thermoplastics, the energy director (ED) joint and the shear joint. An ED is a mold in protrusion located at the joint interface that is used to concentrate the ultrasonic energy at the interface. Industry uses a triangular-shaped ED for simplicity of production. The other type of joint mostly used by the industry is the ''shear joint,'' which is an interference type of joint. Figure 2 shows the two types of joints practiced by the industry.The ultrasonic bond is usually accomplished in two ways, by contact sealing, also called near-field welding (distance from horn is less than 6 mm), and remote sealing, also called farfield welding (distance from the horn is greater than 6 mm), or a combination of both. Figure 3 shows the near-and far-field configurations. Practically all thermoplastics can be contact sealed and components having rigid shapes can be remote sealed. Amorphous thermoplastics like acrylonitrile butadiene styrene (ABS), polycarbonate, acrylic, polystyrene, and polysulfone are rigid and easily welded ultrasonically. As they do not greatly dampen the ultrasonic waves, they can be welded both in the near-field and in the far-field regions. Semicrystalline thermoplastics, on the other hand, are soft and are characterized by regions of ordered molecular structure, which acts like springs in the solid state and absorbs a large part of the ultrasonic vibrations instead of transmitting them to the joint interface. They include high-density polyethylene (HDPE), acetal, nylon, polyester, polyethylene, polypropylene, and polyphenylene sulphide. As they are difficult to weld, especially in the far-field region, attention has to be given to the design of the joint, length of the specimen, and fixturing of parts.A few standard joint designs practiced by the industry to weld semicrystalline polymer HDPE were studied in terms of the interface temperature, collapse, energy absorbed, and strength at fracture to arrive at the suitable joint configuration for welding semicrystalline polymers in the far-field region. The joints were grouped as ED joints and non-ED joints. Simulation of temperature distribution was carried out using ANSYS (ANSYS, Inc., Canonsburg, PA) for the different joint designs and compared with the experimental results. LITERATURE REVIEWBenatar and Cheng 1 studied the USW of thermoplastics in the far-field configuration. They found that both amorphous and semicrystalline polymers had stronger ultrasonic welded joints when the joint interface was at a displacement antinode. Grewell 2 studied the far-field welding of polypropylene and was successful in weldi...

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Optimizing the joint strength of ultrasonically welded thermoplastics

Cited by 37 publications

References 13 publications

On the effect of flat energy directors thickness on heat generation during ultrasonic welding of thermoplastic composites

On the effect of flat energy directors thickness on heat generation during ultrasonic welding of thermoplastic composites

Welding methods for joining thermoplastic polymers for the hermetic enclosure of medical devices

Study of Different Joints for Ultrasonic Welding of Semicrystalline Polymers

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