Composite laminate

A composite laminate is a material made of layers of reinforcing fibers embedded in a polymer matrix, most often epoxy or polyester resin. The fibers are typically carbon (CFRP, carbon fiber reinforced polymer), glass (GFRP, commonly called fiberglass) or aramid (for example Kevlar). In engineering usage, laminates belong to the broader group of composite materials, also referred to as FRP (fiber-reinforced polymer, spelled fibre in British English).

The main advantage of laminates is their high strength-to-weight and stiffness-to-weight ratio. Along the fiber direction, carbon composites can be stronger than steel at a much lower weight. That is why they are widely used in aerospace, motorsport (Formula 1, racing bicycles), spaceflight and high-performance sporting goods.

Laminated parts are made by hand layup of plies in a mold, by resin infusion (vacuum infusion or RTM, resin transfer molding), by autoclave curing of prepregs for aerospace-grade quality, or from thermoplastic composites for fast series production. Each method offers a different trade-off between cost, mechanical properties and suitability for series production.

Design rules for laminates differ significantly from those for isotropic materials such as metals. A laminate's properties are anisotropic, meaning they depend on the orientation of the fibers relative to the load. The correct layup, that is the sequence and orientation of the plies (also called the laminate schedule or stacking sequence), is critical to the mechanical properties of the part.

Laminates are used where low weight combined with high stiffness is decisive: robot arms and drone frames, vehicle and aircraft parts, sports equipment, covers and fairings, blades and beams. Fiberglass is the cheaper choice for covers, tanks, boat hulls and parts that must withstand corrosion and weathering.

Another advantage is the ability to make large shaped parts in small batches with relatively inexpensive molds, and to orient the fibers deliberately along the main load paths.

A laminate cannot be designed like a metal part made of a different material (an approach sometimes called "black aluminum" design). Strength perpendicular to the fibers and between plies is much lower, so holes, load introduction points and joints are critical. Bolted joints need inserts or local reinforcement, and bonded joints need proper surface preparation.

The properties of the finished part depend heavily on the manufacturing process (resin content, voids, layup accuracy). Treat datasheet values as indicative only and plan for testing of load-bearing parts. Ask your supplier about the manufacturing method, fiber and resin type, layup and quality control. Also watch the UV resistance of the resin and galvanic corrosion of aluminum in contact with carbon fiber.