EWI's Plastics & Adhesives Capabilities

Adhesive Bonding | Plastics Welding Capabilities | Ultrasonic Soldering

Adhesive Bonding by George Ritter
Adhesives join materials, often dissimilar, that cannot be welded. Adhesives operate up to ~500ºF continuous with short spikes up to 700ºF. Structural adhesive bonding is common in automotive, aerospace, and marine applications. Small components are often bonded in electronics and medical products.

Adhesive bonding combined with welding methods produces a weldbonded structure. In weldbonding, the adhesive improves fatigue life and shear strength over welds alone. Included welds improve peel performance, a known shortcoming for adhesives.

To date, weldbonded structure programs have focused on steels or aluminum. EWI is uniquely positioned to develop weldbonded applications and has produced structures using resistance, laser, ultrasonic, and friction stir weldbonding methods. Recent bonding programs have developed structures based on aluminum, titanium, steels, and composites. Bonded hybrid combinations have included composites-metals, plastics-metal, film-film, and rubber-metal applications.

The four development stages for a bonded application are: surface treatment selection, adhesive selection, process development, and verification testing, often with required environmental exposures. EWI supports all those requirements and offers integrated engineering services in materials selection, joint design/FEA, NDE, and proof testing. Analytical equipment is available for infrared and thermo-mechanical studies, polymer SEM, and TEM.

EWI’s objective, multi-disciplinary approach to problem solving helps our members find the best joining method. Adhesive bonding is another way that EWI helps you to “get it together”.

Plastics Welding Capabilities by Marc St. John
Thermoplastic materials (polymers) are commonly used in many applications and its growth in usage and newly developed grades is continuously increasing. Although parts made of these materials can be very complex, in most cases they still require part assemblies to be joined, or welded together. EWI’s plastic welding labs are fully equipped with modern welding systems and include the following process capabilities:

• Thermal Processes: Hot Gas, Extrusion, Heated Tool, Resistive Implant
• Friction Processes: Spin, Vibration, Ultrasonic
• Electromagnetic Processes: Implant Induction, RF, Laser/IR

EWI’s plastic welding team has a collective 70 years of experience in thermoplastic materials and the technologies for assembling them. We have served customers from many industry sectors, including medical, automotive, consumer products, petro-chemical, and aerospace. Because EWI does not sell welding process equipment, we are able to provide our customers with an objective perspective that provides them with the best joining options for their applications. Aside from having the capability to evaluate all plastic welding processes, we also provide assistance with designing specific weld joints suited for the welding process being considered, on-site assessments of current welding processes, optimizing welding processes, failure analysis, destructive and non-destructive testing, training, and consulting.

From the design phase through integrating a welding process on the manufacturing floor, EWI will work as an extension of your own engineering team to help achieve your plastic joining objectives in a cost-effective and efficient manner.

Ultrasonic Soldering by Dan Hauser
EWI is developing new techniques for ultrasonic soldering and brazing of a wide range of materials. Ultrasound allows wetting of both metals and non-metals without the use of fluxing agents, and the associated flux-removal operations. While ultrasonic soldering is an established joining process, EWI is exploring new tools and alloys to expand the range of applications. EWI developed the patented tin-based lead-free “SonicSolder™” alloy and has demonstrated it for applications such as joining ceramic tiles to titanium sheet, stainless steel tubing, and electrical componenents.

More recently, other alloys have been explored for applications requiring higher strengths and service temperatures. In this project, EWI’s ultrasonic soldering capabilities were extended from a soldering temperature of about 250ºC to a brazing temperature of 700ºC. Ultrasonic horns were designed and then fabricated and tuned for operation at temperatures of 400ºC for ultrasonic soldering using Zn-5Al filler metal, 600ºC for brazing using Al-12Si filler metal and 700ºC for brazing using pure Al filler metal.

Depending on the alloy used, a range of compressive shear strengths can be achieved. For example, using Ti-6Al-4V base metal the SonicSolder™ alloy yielded 5.2 ksi shear strength and Al-12Si braze alloy yielded 14.6 ksi shear strength. However, microstructural characterizations of brazed joints showed intermetallic-compound formation at the filler metal-base metal interfaces. Some interfaces also indicated voids and oxide particles.

Recommended future efforts should be directed toward higher ultrasonic brazing temperatures, brazing dissimilar metals and metals to nonmetals, assessing methods to mitigate the effect of dissimilar coefficients of thermal expansion, and brazing tubular structures.