Learn about the backbone for any composite structure.
- Advanced Composite Materials are made up of fibrous materials embedded in a resin matrix. Now this is if we are talking about a solid laminate. The orientations of the fiber, and it's alternate directions, give the composite material its strength and stiffness. These strength and stiffness values can be as low as a piece of fiberglass, or as high as a piece of titanium. Because the strength design requirements are a function of the applied load direction, ply orientation, and ply sequence, these things have to be correct. Wrap Clock indicates the longitudinal fibers of a fabric.
The wrap is in the direction which is the highest strength for the fiber. Now, this direction is again going to follow your load path. So the fiber degree zero sets the longitudinal load path and all other fibers are based off of that first direction specified. All products and forms generally begin with a spooled unidirectional fiber or raw fibers packaged as continuous strands.
An individual fiber is called a filament. Most fibers are available as dry fiber that need to be impregnated, impreg, with a resin before use or pre-preg materials where the resin is already applied to the fiber. A roving is a single grouping of filaments or fiber ends. Such as a 20-end, or 60-end glass rovings. All filaments are in the same direction and they are not twisted. Unidirectional, pre-preg tapes have been the standard within the Aerospace industry for many years.
And the fiber is typically impregnated with thermosetting resins. Tape products have high strength in the fiber direction and virtually no strength across the fiber. Bidirectional offer more flexibility for lay up of complex shapes than straight, unidirectional tapes. For Aerospace structures, tightly woven fabrics are usually the choice to save weight, minimizing resin void and maintaining fiber orientation during the fabrication process. Knitted or stitched fabrics can offer many mechanical advantages as well.
Fiber placement can be straight or unidirectional without the over-under turns of woven fabrics. The fibers are held in place by stitching with fine yarns or threads, after pre-selected orientations of one or more layers of the dry pile.
- What is a composite?
- Where composites are used
- Composite materials
- Composite manufacturing methods
- Inspection methods
- Repairing composites