Once considered an exotic material exclusive to upper echelon aerospace applications, carbon fiber based composites are now commonplace in nearly every field of industry. From sports equipment to medical products, manufacturers are taking advantage of composites for their benefits in high strength to weight ratios, ability to conform to complex shapes, resilient fatigue characteristics, and for the energy savings inherent with the dynamics of reduced mass. Additionally, carbon fibers have little attenuating effect on x-ray radiation, lending itself well to many x-ray medical and non-destructive testing applications. Because composites can be molded into very complex shapes, 3D CAD/CAM has become the standard from which parts and tooling is designed and manufactured. Apex Designs has been designing and manufacturing a wide variety of carbon fiber components for automotive, medical, and defense applications for over a decade. Core strengths are component design, tooling design, and production manufacturing by compression molding techniques. In house manufacturing services include oven cure and compression molding with pre-preg materials, and wet layup techniques with room temperature cure epoxies.
Wet layup and vacuum bagging methods are an economical choice for relatively low volume parts. Because this method utilizes room temperature resin cure systems, lower cost tooling can be manufactured from virtually any kind of mold material. During wet layup construction, dry woven fabric plies are placed into the mold and impregnated with a liquid resin agent by hand using a combination of squeegees, brushes, and rollers. Each ply of carbon is carefully "wet out" and inspected for entrapped air before the next ply is placed. Once the ply schedule is completed, the part is placed in a bag and placed under vacuum pressure until the part has cured. Vacuum bagging forces the plies of carbon against the tool, eliminating trapped air pockets, and removing excess resin. Wet layup techniques are popular in the experimental aircraft and amateur racecar industries.
Pre-preg construction with autoclave, oven, or compression molding methods are reserved for parts and assemblies that require the highest strength to weight ratio achievable. Military aircraft, wind turbines, Formula 1 racecars, and laboratory centrifuge buckets (Download Carbon Fiber Centrifuge Buckets Brochure.pdf) are just a few examples of products that take advantage of pre-preg carbon fiber’s strength to weight ratio. In pre-preg construction, woven carbon fiber fabric is pre-impregnated with an epoxy resin system that requires elevated cure temperatures typically above 250 deg F. Because the amount of resin impregnated into the fabric is closely controlled to its optimum amount, pre-preg materials yield components that are lighter than parts manufactured using wet layup techniques. Additionally, because pre-preg does not cure at room temperatures, fabricators have considerable more "open time" to complete the lamination process, assuring that the fiber's orientation is meticulously aligned to optimize the strength of the part. Unlike wet layup techniques, pre-preg remains tacky during the lamination process, allowing each ply to stay firmly in place which assures proper fiber alignment and aids in the preparation for the curing cycle. Curing cycles are achieved with carefully controlled temperature cycles in ovens or autoclaves. Depending on the part size and resin properties, full cure can be achieved in as little as 1 – 2 hours. Tooling for pre preg parts can be manufactured from aluminum, hi temp carbon fiber, or tooling block. Apex Designs has developed a specialized hybrid silicone tooling procedure that aids in the construction of parts with deep drawn walls and little draft.