Auto Racing Composites
Roush Racing takes us viewers on a tour through their composites shop in a short clip from Roush TV.
Using mostly carbon fiber and kevlar reinforcements, Roush Racing fabricates many different components for the racing industry using epoxy resin systems. Ranging from the front noses for the NASCAR Car of Tomorrow car to drag racecar bodies and small ductwork, Roush Racing’s composites shop does all sorts of fabrication.
The race shop includes two different fabrication processes. Wet layup vacuum bagging is used for some parts, while others are made using prepreg material that goes into an autoclave.
The video tour is well done, and includes everything from the Eastman material cutter to the fabrication process, bagging process, and trim. We also get to see some of the finished parts after they are demolded and trimmed.
These parts are very expensive to manufacture, due to the high cost of materials and labor. Tooling and equipment costs for this type of process are somewhat reasonable, with the exception of the autoclave and the automated cutting table. Composites fabrication of this caliber is labor intensive, but can produce very unique parts that are lightweight and strong.
Use of FRP Composites in Bridges
FRP (Fiber Reinforced Composites) have been successfully used in the construction and repair of transportation bridges in the U.S. for several years. These projects have proven that the materials and work methods are can be successfully used.
FRP rebar can replace steel rebar and provide equal physical strength while eliminating the corrosion problems of having steel embedded in concrete.
Prefabricated bridge decks made of FRP in a factory can be quickly and easily installed in the field to save time and money during the bridge construction project. The large panels are shipped in and laid down, ready to use very quickly. Concrete cure and inspection times are reduced.
Concrete crack repairs can be made to bridges and concrete structures by wrapping them with composite materials to seal these cracks and hold the concrete together, protecting it from further damage.
This technology has been in development for many years, and proper materials, construction techniques, and design guidelines have been established to allow for many successful projects to be completed.
Economics play a considerable role, and this cost comparison constantly changes with the prices of materials on both sides. Composites have the advantage of typically requiring fewer road closures and construction time in the field.
Vacuum Bagging Video
Vacuum bagging is a process that requires unique materials and processes, but can be simple to operation in an ongoing basis.
There are many advantages to vacuum bag molding, a few of which include:
- Improved resin/glass ratio
- More consistency across the laminate and part -to -part as compared to open layup
- Containment of air emissions from the resins
As compared to hand layup and chop layup, there are a few disadvantages, including
- Higher consumable material cost
- Higher capital equipment cost
- Difficulty with superior surface finish
Some parts are more suitable for vacuum bag molding than others. It also depends upon which process it is being compared with.
Vacuum bag molding requires an extremely tight seal between the mold and the bag. Molds with multiple pieces or holes for inserts can be difficult to complete a seal.
Parts that are overly large and complex can present challenges with placing resin and reinforcement before the cure cycle starts. The bag must be completely sealed and under full vacuum before the curing cycle of the resin begins.
The basic premise of vacuum bag molding is that the air is removed from the bag, allowing the atmosphere (air on the outside of the bag) to push the bag onto the part on the mold, compressing the layers of resin and reinforcement. Many misinterpret the process as “sucking the extra resin out.” We are merely allowing the laminate to be compressed by the weight of the air above us in the atmosphere to consolidate it before cure. The excess resin is usually absorbed by extra layers of sacrificial material inside the bag.
IH Hood Video
Several other posts have documented the work I performed on my 1993 International Truck Hood. I also took some video and recently got it all put together and posted on Youtube. Hopefully you can learn a couple of things.
The SMC hood was ground in preparation of work, and then I used epoxy and fiberglass to complete the work and restore the structure and shape back to original for this truck hood.
IH Hood Repair– Passenger Corner
One of the repairs on my International Hood was for the passenger corner. This portion of the hood was damaged before I got it, and was COMPLETELY MISSING!
Time, effort, epoxy, and fiberglass, allowed me to successfully completed the repair. This SMC hood will be repaired as good as new!
Damaged area to be repaired
The hood was placed upside to allow for work access. The repair area had several cracks and breakage areas. The repair began with surface preparation.
Surface Preparation on the repair area
I used a grinding disc to remove material on the front and back side of the repair to scarf the repair into the large area. Good surface preparation gives us a clean area that can hold a bond and create a transition area. I also drilled some holes in the end of the cracks to stop their propagation.
The back side was prepared too
The back side was prepared for repair by grinding the surface to allow for good bonding by the epoxy resin and glass reinforcement.
Beginning to add material
I started to add epoxy and fiberglass back onto the fender. I had to gradually move back out to where the existing fender used to be. I worked both sides bit by bit and allowed it to start curing before adding more.
Getting the shape back
I actually went a bit beyond the shape I needed. This allowed me to get the surface planes in the right spot, and later return and trim back the proper hood edge.
Back side getting rebuilt
The back side of the repair also got transitioned into the hood and out to meet the front repair area.
Grinding the repair
After most of the rebuilding was complete, some grinding got it back into shape to allow an evaluation of the repair progress.
Grinding on the back
The back side was cleaned up as well, getting the appropriate part thickness back to where it was originally intended. A nice transitioned surface was created, and all sharp edges were removed.
Bodyfiller for cosmetics
I used some bodyfiller to smooth the repair and restore the cosmetics of the hood. I could also have used epoxy, and it would have bonded better. Polyester bodyfiller is less expensive, easier to apply, and easier to sand. I smoothed the surface and feathered it back into the surrounding area to allow for a consistant surface.
Application of Primer-Surfacer
Urethane Primer-Surfacer is applied to the whole area to allow for removing the sanding/grinding scratches and preparing the surface for paint application.
The repair is complete, and the hood looks back like it was original. This repair, and many others, can be detected with some investigation of the back side of the repair area. This will be a very durable repair and will last as long as the rest of the composite body panel.