Rocketry airframes are made from a number of different materials, the most common being cardboard tubes. Among cardboard tubes, the two predominant types are what is called kraft cardboard and phenolic.
Kraft cardboard tubes are usually a thin walled spiral-wound tube made from layers of paper glued together in a spiral pattern. Most tubes commercially available for model and high power rocketry also have a smooth glassine covering on them to make finishing easier. Kraft cardboard is the most wide spread due to the low cost, yet it is the type of tube most likely to experience damage on landing.
Phenolic tubing is basically kraft cardboard that is impregnated with phenolic resins, a tough, durable substance that waterproofs and strengthens the cardboard. Phenolic rockets have been known to land in ponds and lakes and still be flyable once retrieved due to the toughness of the phenolic resin. While having very high compression stength, standard phenolic tubes are very brittle and can shatter easily. Newer brands of phenolic tubing are being made that is flexible, allowing up to 50% compression without breaking.
More recently, there have been new phenolics such as the seamless linen phenolics that offer very high strength and no spiral lines to fill.
While used to a lesser degree, the best tubing available are varieties of composite tubes. The most wide spread composite tubes are G-10 fiberglass and has superior strength. Other composite tubes also available are variations of kevlar or carbon fiber, which offer the most strength per square inch. Composite tubes offer the highest strength but cost the most money.