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.

Liquid Bulk Transport Tanks

Lincoln Composites has introduced their Titan™ Liquid Bulk Transport tank.  This unit is comprised of four composite tanks that meet the specifications of a universal shipping container, allowing for transport via ship, rail, or semi on existing infrastructure.

TITAN Gas Transport

The tanks are require three basic parts to complete the engineering challenge.  An inner liner made of High Density Polyethylene provides an impermeable layer to hold the gas.  Next, a filament-wound composite shell made with epoxy and carbon fiber contains the pressure of the gas.  A Polyurethane coating on the outside of the tank protects from moisture and abrasion.

The system is designed for Natural Gas, Hydrogen, Argon, Helium, Nitrogen, etc.  Existing transport via semi truck is accomplished with large steel-tanked semi trucks that are heavy and prone to corrosion.  The TITAN composite solution allows for multiple transport options (rail, ship, semi) as well as lower tank weight.  The gas stored versus the tank weight is a huge advantage over steel tanks.

Lincoln Composites claims that traditional steel tanks hold 4000 SCM less CNG than the TITAN™ and weigh 16,000 kg more than the TITAN™ composite tanks.

For more information, check out the Titan page at Lincoln Composites.

Weathered Filament Wound Pipe

I recently had the opportunity to examine some weathered composites in the form of fiberglass pipe.  There are some very important observations to be made from visual clues.  One of the difficulties with too much analysis is the unknown history with the original manufacturing process, materials, and intended application.  We also do not know much about the actual use and environmental exposure history.  These factors would be great to have, and could probably give us additional data regarding the degradation of materials.

Here is the picture showing the pipe in an outdoor setting where it has rested for at least twenty years.

weathered filament wound pipe

The exposed pattern is showing that the outer layer of resin has weathered away, leaving the white strands of fiberglass exposed.  It is pretty minimal loss, likely just a few thousandths of resin is missing.  The weathering has nicely exposed the crosshatch pattern of the filament winding process to see the angles and directions that were used.  An old pipe joint can also be seen at the top of the picture.

Many physical properties could be tested on this fiberglass today, but would be pretty useless without a baseline for comparison.  Armed with data as to the original strength, materials, and processing characteristics, it would be interesting to test the loss of properties such as impact resistance, shear strength, load fatigue, etc.  Many products undergo aging and weathering testing before final design approval, but do so in an accelerated fashion.

Intro to Filament Winding

Filament winding is an open molding process that is automated by using a rotating mandrel as the mold. This mandrel acts as a male mold which allows for the control surface to be on the inside, and the outside diameter size being dependent upon the laminate schedule.

The reinforcement to resin ratio can be very high with filament winding because of the automated nature of the process. Very high tensile strengths can be achieved depending upon the use of materials and their orientation.

Products that are manufactured include chemical storage tanks, pipes, stacks, pressure vessels, and rocket motors. Lightweight storage tanks have been a real area of growth as of late. The use of these high pressure vessels has been applied to air packs for firefighting as well as Liquid Natural Gas storage devices for alternative fuel vehicles.

The process works by feeding continuous strand roving through a resin bath and winding it onto a rotating mandrel. This feed mechanism traverses the length of the mandrel to create a predetermined geometric pattern. After sufficient layers have been applied, the laminate is allowed to cure on the mandrel before the molded part is stripped away to begin another.

Industrial Corrosion applications

A lot of FRP materials are used in the chemical and industrial sectors of the economy. The non-corrosive and non-conductive properties of the fiberglass materials have many advantages over steel and other materials.

Large tanks, pipes, and structures are fabricated both off-site and on-site of the final installation. The best quality comes from the controlled environment of the factory. However, the physical size may necessitate that structures are built in pieces for transport and installation. They onsite workers can join the pieces to become one. There are several joining methods, including adhesive, mechanical, and chemical bonding (fiberglass tabbing).

There are specialized resins used for these corrosion applications. These resins are the best at resisting chemical interaction, and are made to have high impact strengths to resist failure of the overall structure.

Fiberglass resin and glass is normally non conductive, both with heat and electricity. This can be adventageous for negating concerns for electrocution. The flipside is that static electricity can build up and discharge randomly in a search for a grounding path. Heat conduction is poor so it can act as an insulator and heat sink.

Many of the pipes and tanks are manufactured using a process called filament winding. This is a process where a round mandrel acts as a mold and rotates on its center axis. Reinforcement is wetted out with resin and fed onto the spinning mandrel in specific orientations for strength requirements. The part is allowed to cure and the mandrel is removed.

The matching of these materials to their specific application, use, and environment is extremely important. And it can be an area where composites can shine.