Bonding

Bonding applications in the automotive industry - Henkel Adhesives.

HOW TO: BONDING

 

Bonding applications in the automotive industry have increased significantly during recent years. Learn everything you need to know about bonding, e.g. for side panel replacement or roof repair in special OEM laser-brazed roofs, and particularly bonding in vehicle body repairs, applying OEM-approved repair methods.

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Bonding in modern vehicle constructions

Lightweight constructions & torsional stiffness

Additional corrosion protection

Bonding: Additional Knowledge

Learn everything you need to know about the subject of Bonding.

Aside from the more common joining methods, modern vehicle constructions also make use of advanced adhesives. These offer a range of advantages, opening up new possibilities in the fields of vehicle design, construction and safety engineering.

1.1 Car body joining methods

 

1.2 Advantages of joining with adhesives

• No substrate damage
• Joining of dissimilar substrates (e.g. steel with aluminium)
• Unimpaired structural integrity
• Even load transmission
• Uniform stress distribution
• Noise and vibration reduction
• Additional sealing prevents water and moisture from penetrating between joined parts, thus eliminating a major cause of corrosion.

Benefits of structural bonding
• Torsional stiffness
• Shear strength
• Impact resistance

Structural adhesives are used on metal components such as top-hat profiles/arrester rails and reinforcing panels in order to achieve a high level of structural stiffness or improved crash performance in vehicle bodies (so-called “bodies in white”). Studies show that adhesive-bonded or hybrid joints exhibit higher durability and better stiffness retention than their spot-welded equivalents, thus contributing to long-term driving comfort. Bonded structures have a higher energy absorption and deformation capacity in crash situations than conventionally joined parts.

• Adhesives increase body stiffness and improve travel comfort
• Adhesives result in increased energy absorption and enhance safety

Benefits of flexible bonding
• Vibration reduction
• Compensation for dissimilar coefficients of expansion
• Noise absorption

In car body constructions, there are also applications where flexible joining methods are required. For adhesives to be effective in such applications, a certain gap width is required which they then fills to produce a flexible barrier/cushion offering resilience and force absorption.

Bonding applications in the automotive industry - Lightweight constructions and torsional stiffness.
Bonding applications in the automotive industry - For effective adhesive bonding, a certain gap width is required for

Two-component adhesives cure irrespective of the environmental conditions. They cure as a result of a chemical reaction between the two mixed components. One-component adhesives have different curing systems. In the repair market there is widespread uses of one-component adhesives that cure in response to moisture and temperature.

Two-component epoxy and polyurethane adhesives

Bonding applications in the automotive industry - 2-component versus 1-component adhesive technologies.

Two component adhesives cure irrespective of environmental conditions due to the chemical reaction that takes place between the two mixed components A and B. Accelerated curing brought about by increasing the object temperature is possible and frequently practised (e.g. through the use of heating pads, infrared heaters, ovens etc.). Heat curing can also increase the final strength of the adhesive. Always check the technical data sheet for product specific curing information.

One-component technology for polyurethanes and MS polymers

One-component adhesives cure at room temperature and with humidity. Skin formation: 3-4 mm in the first 24 hours at 23°C and 50% relative humidity.

Polyurethanes and MS polymers cure from the outside inwards.

One-component polyurethane and MS polymer adhesives have the same curing process.

The curing time depends on the layer thickness. An increase in temperature and moisture can reduce these times, whereas lower temperatures and low relative humidity have a retarding effect.

The higher the humidity and temperature the faster the cure.

Bonding applications in the automotive industry - One-component technology for polyurethanes and MS polymers.

Henkel car body adhesives
• Provide excellent corrosion protection and adhesion
• Offer process-adjusted application times
• Comply with the specifications of original car manufacturers
• Meet OEM/OES requirements regarding strength and crash performance
• Offer exceptional safety based on extensive research and OES experience

Corrosion protection
Two-component TEROSON EP 5055 adhesive has excellent corrosion protection properties.
Pictures show situation after several salt spray cycles.

Bonding applications in the automotive industry - Bonded area exhibits no corrosion with TEROSON EP 5055.

• Bonded area exhibits no corrosion

Practical example:
• Bonded roof with OEM-specified TEROSON EP 5055
• Excellent adhesion without primer
• Dismantled after 3 years in use

Result: no corrosion whatsoever

Bonding applications in the automotive industry - Practical example of TEROSON EP 5055: no corrosion!
Bonding applications in the automotive industry - The non-bonded joint is totally corroded.

By comparison:
• Non-bonded joint is totally corroded

DO:    Surface preparation
Mechanical preparation by deburring, sanding and straightening the components improves surface suitability. Grinding removes loose and deformed parts as well as obstructive layers and forms an even surface. Depending on the substrate, this may also improve adhesion.
The surfaces to be bonded must be cleaned of oil, grease, moisture and coarse dirt. TEROSON FL+ can be used for this pre-treatment.

DO:    Correct mixing of two-component adhesives
Only use cartridge guns that feature a piston rod. Prior to fitting the static mixer, extrude a small amount of the material so as to ensure that both components are being discharged simultaneously. Now, fit the static mixer. Discard the first approx. 10 cm of extruded adhesive so as to make sure that the adhesive actually being applied is properly mixed.

DON’T:    Move workpieces or place under stress during curing.
While the adhesive is curing, the bonded parts should not be moved or stressed and must stay in exact position. This will ensure that the curing process is uninterrupted so as to achieve maximum final strength and adhesion.

 

It is important to consider every aspect of a job when determining its real cost. Hence any calculation should take into account things such as:
• Material cost
• Time saved
• Energy saved
• Supplementary products required or used
• Tools