Panel Stiffness
Composites structures have requirements for stiffness to provide support and stability. Tests can be completed to identify the stiffness of a given area on a composites structure, i.e. how much it will bend for a given force.
The required stiffness of a section of a composites part depends upon the overall design and service expectations. Several factors, including the life expectancy of the object, the load rating of the composites surface, the inter-laminar bond strength, will help determine the threshold requirements. Testing is very important to determine the life expectancy of the part and whether it meets the requirements of its’ job.
Panel stiffness can be modified to meet these requirements using two basic methods. One way to increase the stiffness of an unsupported composites panel is to reduce the size of the panel through additional support structures. The other way is to increase the panel thickness across the same area. Choosing which method to use depends upon the engineering of the part and determining which method is acceptable with the surrounding part layout. If there is room to add supports, this is likely a quick and easy option. If there is room to increase the thickness, adding new or additional coring materials may be a simple solution.
Building a strong and stiff composites structure can be accomplished with the extremes of building a robust “skeleton” with small open areas and a thin skin, or having a basic, limited “skeleton” with a heavy duty cored laminate that supports itself.
A combination of the two usually works out best.
5 Axis Filament Winder
Filament winding is a process that can be used to create round fiberglass shapes with exceptional strength characteristics. Used for piping, tubing, and tanks, filament winding is normally an automated process that has computer-controlled equipment to place glass and resin around a mandrel- the piece that functions as the mold.
There are many variables that can be modified for filament winding, and these will affect the strength characteristics of the finished piece. The angle of the glass, number of passes (thickness), use of glass mat, and type of resin will affect the finished product strength characteristics.
I found a short video that demonstrates the equipment and the process.
As you can see, the glass is applied in a consistent manner across the part, allowing for uniform strength characteristics. As you can see, this is yet another process that the composites industry uses to create useful products with advantages over those of competitors.
Machining Composites CNC Video
Much like other materials can be machined, so can composites. Everything from basic fiberglass fabrications to advanced composites materials can be machined to add details and features.
This can be accomplished using hand-held tools guided by fixtures and measurements. Hand tools such as air routers, drills, and saws. A disadvantage is that the operator can commit errors and must be protected from safety hazards. These hazards include airborne dust, bending strain, lifting strain, and physical cuts.
For high volume or high precision applications, there are CNC routers that can be employed. These are fast, efficient, and safe. They may be expensive though.
Several manufacturers make CNC routers, and Thermwood is one as shown below.
This video shows several different applications and parts that can be routed with this large Computer Numerically Controlled machine.
Carbon Nanotubes
There has been lots of discussion in the last few years about the promise of nanotubes, especially those made from carbon. These microscopic particles can be used to create new properties and materials that will improve products in society.
This video discusses “Buckypaper” developed at Florida State University. University research is always intersting, but finding practical applications is sometimes difficult. This video does discuss a few real-world uses for this material.
Fiberglass vs. Aluminum
A great Youtube video where testing was used to compare aluminum and fiberglass composite panels. This really helps to show the superior characteristics of the fiberglass.
This video covers a quick resin infusion example, repair of the damaged laminate, and other useful information. Peel strength and impact testing is covered, and demonstrates the superiority of fiberglass laminates over aluminum.