Follow these steps to identify aluminum, foams, laminated steel and tailored blanks

We're hoping to make life a bit easier with the following quick guide. As always, you will still need to locate the manufacturer's repair guidelines, but oftentimes, just knowing what kind of repair you're looking at is actually half the battle.

Aluminum

Aluminum cannot be formed in what is known as deep draw molds as easily as steel. Softer aluminum alloys can be pushed into those deep molds successfully, but they don't have the mechanical and corrosion-resistance properties engineers need. Harder alloys tear and crack. In a very new technique, one vendor has produced an ingot of aluminum that has a softer alloy in the center and harder alloys on each side. These ingots are rolled into sheets that have a sandwich of hard and soft aluminum in one sheet. This allows deep draw tools to be used to produce inner door shells for the newest BMW 750i.

Since the doors represent 20 percent of the body-in-white, or the shell without any mechanical or trim, this is an important application. Doors have grown in thickness over the years as speakers, window motors and intrusion prevention components take up space. Developing a way to make very lightweight door shells was a design goal for the new model. For shops, full part replacement is the preferred repair process.

Modular components make vehicle repair much more manageable. One trend that has been growing is modular crush zones. In many moderate hits, only the first several inches of a front frame rail is damaged when properly designed with collapse deformations. By making this area of the frame easy to replace, repair costs can be managed better.

Some GM SUVs have had this for some time. The little cap that welds or bolts onto the front of the frame rail is hydroformed to a shape that is able to collapse into itself and absorb a lot of energy. BMW and Mercedes-Benz use bolt-on aluminum crust caps, making replacement much easier. Aluminum is lighter in weight and does not have to be formed with extensive deformations to produce very predictable crush performance.

CHALLENGE: One somewhat controversial engineering exercise is the use of aluminum and steel in the same vehicle. Where components are bolted on, this has new impact on the repair process. When the parts are welded, bonded or riveted on we need to know how to replace them. In the case of the BMW 5 series, the body is steel up to the firewall. From there forward it is aluminum. The factory process uses rivets and adhesive to attach the front structural components.

The factory recommendation is to replace the aluminum parts if they sustain much damage in an accident. A stud is spot welded to each rivet and pulled out with special equipment. Then the frame rails can be removed. New components are riveted on with adhesive. One quirk is that a hole must be drilled and a steel fastener screwed in to assure that the ground path is maintained. A technician must attend a class from BMW on the process, and the shop must purchase a special spot welder to work on this vehicle.

Foams

Foam has become a solution to many engineering challenges. Ford uses a structural foam to solve a weakness in some of its SUV floor systems. The foam must be heated to become thin enough to squeeze through the intermix nozzle. It hardens to a concrete-like material. Inserted into some of the hat sections, it provides local support and prevents buckling. The repair technician has to chisel out the old material and have a map of where to squirt the new stuff.

Much more widespread is the use of rigid or flexible foam to reduce what the industry calls NVH (noise, vibration, harshness). Other uses include protection placed in doors to absorb energy in the case of a collision. Some is replaced with two-part material and some comes as a molded part.

CHALLENGE: Whether structural, safety or just related to how quiet the vehicle is, we must pay attention to what kind of material is used and precisely where it is placed so we can restore the vehicle.

Laminated steel

Laminated steel is an interesting material that seems to be surrounded by quite a bit of confusion. A very thin sheet of plastic bonded between two sheets of steel results in a material that is easy to form and greatly reduces the bell-like quality a thin piece of steel can have. "Quiet Steel" is one trademarked name for laminated steel. Firewalls were an early application to keep engine and road noise out of the passenger compartment. Wheel wells and those little seat pockets and storage areas in minivans are made from laminated steel.

CHALLENGE: So how do we repair it? We can pound on it like "normal" steel, but if we need to replace a component, there are different options. Chrysler says to glue seat pockets back in with windshield urethane. GM has a document with general guidelines for repairing laminated steel. In part it reads:

• The use of heat to repair damage is not recommended for this type of steel.
• This type of steel should be replaced at the factory joints. Sectioning or partial replacement is not recommended.
• This classification of steel cannot be used as a backing reinforcement or a sleeve for a sectioning joint.
• The use of MIG Plug and Stitch Welding is not recommended for this type of steel.
• The use of MIG Brazing is not recommended for this type of steel.

It goes on to recommend adhesive bonding and rivets to replace factory spot welds, following specified procedures per vehicle.

Tailored blanks

A tailored blank is a stack of steel or aluminum that is laser-welded and then formed into one part. Tailored blanks were an early innovation. As high-strength steel became available, engineers looked for ways to use this expensive material effectively. By combining high-strength and ultra-high-strength steel in a stack, then stamping them in a single operation, they were able to make vehicle side members meet and exceed side impact regulations as they came into effect in Europe.

CHALLENGE: Tailored blanks are far more efficient to manufacture, but they cannot be repaired where there are multiple layers. Little tell-tells like a slight surface distortion left by the laser and the tiny change in thickness where additional layers start and stop are very hard to spot once the primer and paint is applied. When various types of steel are included in one component, like a B pillar or a frame rail, often the OEM option is to replace the entire part. We must increasingly consult OEM repair guides to know where to cut and weld replacement parts. The good news is that some designers are considering the repair situation and including markings to indicate cut lines on the original and replacement parts. Repair processes are available from most manufactures to guide replacement procedures.

Final word: Cooperation

As engineers seek solutions to design stronger, lighter and quieter vehicles and OEMs look for economical ways to manufacture them, both create repair challenges for shops. That doesn't mean they should stop looking for better ways to make better vehicles. They key is working closely with repairers to make sure we can do our job.