Automotive Application: Pickup Box
Fiberglass Composites have been used for ages in the automotive industry. There are advantages to doing this, including corrosion resistance, impact resistance, and weight savings. Toyota pickup trucks from the late 1980′s were made with steel sheetmetal beds that are very rust-prone in winter climates, especially those with salted roads. The response was to use a material that did not rust–fiberglass!
Toyota Pickup Box
This Toyota pickup box has fiberglass sides to eliminate the corrosion problem. The floor and front bulkhead are steel, as well as the missing tailgate. Using composite surely eliminated the rust problems associated with these vehicles, especially since it was used in the most apparent cosmetic areas that are most visible.
This pickup bed is not on a truck, because the frames of these trucks were also extremely rust-prone as well.
Fiberglass Fertilizer Box
Composites’ resistance to rust and harsh chemicals along with the ability to form complex one-piece shapes allows for its use as a fertilizer box on an old corn planter.
This piece was removed from the original International Harvester corn planter, but not because of any problems with the fiberglass! You can see the weathered appearance of the unit from the many years of weather exposure. Glass fibers cover the surface as the resin has eroded away.
The design of this piece included a top lid and a mounting/feed base. Made entirely of one piece, it has remained structurally sound and durable for its purpose. The harsh fertilizer chemicals and weather conditions have not affected this piece to the point of failure.
Removable Blazer Roof
One of the original composites applications in the automotive industry was removable roofs on Chevrolet/GMC K10 Blazers in the 68-72 years, which continued on the Blazers until about 1991. The one-piece composite roofs were durable and relatively lightweight, and way too complicated to be made of steel. Their resistance to rust has left us in the northern states with only the tops left to the Blazer.
This composite part has some mold and mildew on it, but is still mostly as structurally sound as the day it was manufactured. It still has the side windows installed and has clearly sunk down into the grass and dirt, but I am sure it could be lifted out and sanded and painted and re-installed on a vehicle. Good as new!
Composite electrical box
One of the composites applications that I found in a junkyard was a composite electrical box. It was discarded from a former use as an enclosure for electrical equipment in an industrial factory. Other than some minor discoloration and all of the holes from conduit, it is as good as the day it was new.
The advantages of using composites in this application include non-conductivity, protection from impact, and the ability to resist corrosion in tough environments. This is why it has outlived it’s factory setting.
Composites enclosure
An item like this where it has a good surface finish on both sides is going to be made in a set of matched-mold dies in a high-pressure and high-temperature press. It is likely to be manufactured with the Sheet Molding Compound (SMC) process, though Bulk Molding Compound (BMC) could also be at work.
Electrical panel enclosure
You can see on the front door all of the holes from its former installation. Holes on the side were used as well. It was customized for its application with all of the holes, and a new unit would arrive “blank,” without holes, as most applications are customized. The composite can be cut and drilled with metal working tools such as drill bits, holesaws, and saw blades.
Working with Bondo
Commonly referred to by the trade name of “Bondo,” polyester body filler is used by autobody shops to achieve cosmetic repairs on automobiles. It is relatively inexpensive, easy to work with, and achieves good results when used properly. It is basically polyester resin that is highly filled to create a thick paste which can be turned into a solid with the addtion of a hardener.
I have been using autobody filler since age 14, and am finally getting good at it! Just kidding. It is more art than science, and practice makes perfect. Basically, a surface needs to be properly prepared to achieve good adhesion. Then the filler is applied after being mixed with hardener, and allowed to cure afterwords. Some fillers can be sanded as soon as 20 minutes after application.
Basic setup and tools
The basic setup is a working board surface to mix the bondo and hardener. The mixed material is applied with a squeegee or putty knife to fill in low areas. They also aid in cleanup, along with some paint thinner to clean the tools.
Hardener added
Mixing the hardener starts the application window from where the material goes from liquid to solid. The hardener is a peroxide paste that directly affects cure time along with temperature. Too little hardener can also cause poor physical strength characteristics along with difficult sanding properties.
Uniformly mixed
The hardener must be uniformly mixed before it is applied. This prevents lots of problems down the road.
Applied to surface
The body filler can be applied with putty knives or squeegees to achieve the desired affect. This polyester bodyfiller will shrink during cure, so filling high is typical. The flip side is that all of the high spots must be sanded back down, which is wasting filler and time, so it is a fine line to walk.
Working with body filler can be frustrating for the beginner who must practice lots of patience. There are many important aspects that must be followed, just like all composites materials processes. Autobody filler requires proper surface preparation, mixing and metering of materials, and attention to details in order to avoid future problems.
A couple of other practices I recommend is to always wear a dust mask, keep the body filler dry, and only apply bondo over sanded bondo. Some like to just build layers without sanding the lows, and this can lead to adhesion problems.
Hood Repair– A big hole!
My IH SMC truck hood project involved repairing a large hole. This was one of my largest hurdles to the whole project. This is what I initially saw.
The Big Hole
The picture is showing the hood upside-down on a work table. The hole is the result of some sort of long-ago impact the shattered the composite material and did significant damage. My first reaction was to just repair it from the backside. This hope was lost when I quickly discovered that there was not any access to the backside of the repair. At least not without cutting some support structures out of the way. Which would mean that I would need to rebuild those after I repaired the hole. Not impossible, but it seemed like a lot of work.
I began this repair like any other, with the surface preparation. The hole got larger as I removed all of the damaged material and created a transition area.
Damage is removed and transition area prepared
The edge of the hole was a razor’s edge as I transitioned out to the existing finished surface. I also used some sandpaper to sand around the inside of the hole to allow epoxy to adhere to the inside surface when I put in my patch.
My strategy was to create a thin layer of composite using epoxy resin and 3oz Chopped Strand Mat. The layup was done on a piece of plastic and allowed to cure. Once cured, I cut it to be about 1/2 inch larger than the hole. Then I mixed up some thickened epoxy and applied it around the perimeter of my patch and placed it in the hole. I had already placed a sheet metal screw in my patch, and attached a wire to a support to hold the patch in place until cure.
Patch in the hole
In the picture you can see the patch, the wire, and the support. The tension on the wire held the patch in place until the patch was cured in place. Next I worked to add material from the front to fill in the low spot. This returned strength to the laminate and restored the surface profile back to where it should be. I again used 3oz Chopped Strand Mat and started with small diameters and worked out to larger ones until the surface at the correct level.
Most of the Glass and Resin have been applied
Now most of the surface has been filled in, and it can be ground to remove any high spots, air bubbles, and allow for adhesion of the next layer.
Grinding the surface
Now I can fill the low spots with thickened epoxy or bondo and sand the surface to match the surrounding areas and get a nice finish.
This is how a repair should be made. A nice transition in the existing laminate will keep the repair from cracking or breaking in the future. After the bodywork is complete nobody will know it was repaired.
Fiberglass Grating
A composite product that I have worked with in the past is fiberglass grating. Made of composite fiberglass and resin, this material is used as a flooring and walkway material in many applications, and especially for industrial corrosive environments. It may also be used for things like waterfront docks and car washes.
Fiberglass Grating
I photographed a piece in the standing position, but normally it is laid flat as a walking surface. This walking surface may be suspended over equipment or placed directly on floors where walking hazards are present. This material is non conductive and non magnetic, very durable and very stable.
The grating is available in several resin forms for varying degrees of cost and performance suitabilities. It can be cut with sawzalls and circular saws and should be held in place with bolts or brackets. Like most composites, it is very impact resistant compared to other materials. It does have its limits, however, and should be inspected on a regular basis for cracks and deterioration.
The fiberglass grating is available from several manufacturers in different colors, thicknesses, resin formats, colors, and structural properties. Like many other composites products, there are lots of variables to consider and lots of solutions available. The nature of composites allows for custom and specific solutions to meet the needs of the end user.
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