Pultruded Profiles

Because of the relatively thinner diameters of its strands, carbon fiber weighs approximately half as much as fiberglass. However, this difference may not be that significant when comparing equivalent pieces of pultruded fiberglass and pultruded carbon fiber, since the resin adds a significant amount of bulk, generally outweighing the fibers themselves in both cases.
Carbon fiber also exhibits a greater fiber strength than fiberglass. Yet as with the weight difference, this strength difference is not necessarily a significant factor on its own.
For instance, carbon fiber has a fiber strength of 4127, while the type of fiberglass known as E Glass has a fiber strength of 3450 — roughly 16 percent less.
Yet the differences between the two materials come into focus when you consider these factors in tandem. The strength-to-weight ratio expresses how strong each material is relative to its weight.
E Glass has a strength-to-weight of 564, while carbon fiber has a strength-to-weight of 1013 — nearly twice as great.
This high strength relative to weight means that manufacturers need to use far less carbon fiber when pultruding a given product. As a result, pultruded carbon fiber products can often get away with significantly thinner cross-sections.
This is where the real weight reduction comes into play, since less resin will need to be used.

In addition to being stronger than fiberglass, carbon fiber is also stiffer. This extra rigidity can prove highly useful, allowing manufacturers to meet far more precise stiffness needs.
For instance, the silicon tracker modules inside of CERN's Large Hadron Collider required a degree of stiffness that only carbon fiber pultrusions could supply.
However, this increased rigidity does not necessarily mean that carbon fiber makes a better choice for all applications.
Fiberglass with its relatively supple nature is a far better choice for applications that entail high flex patterns. The small flex window of carbon fiber may preclude its use for such applications.
Just as with the relationship between weight and strength, the rigidity of a pultrusion material affects its long-term toughness.
Fiberglass is generally considered tougher than carbon fiber, since its more flexibility nature allows it to withstand stress and physical abuse more easily.
Carbon fiber, despite being stronger, usually has a lower breaking point, making it more susceptible to damage over time.

Compared to materials like steel and aluminum, fiberglass has a relatively small coefficient of thermal expansion — meaning it won't get significantly larger as the result of temperature changes.
That said, if exposed to extreme enough variations — or if tolerances are especially tight — then fiberglass pultrusion may not make a suitable choice.
Carbon fiber has a remarkable property in this regard: it actually has a negative coefficient of thermal expansion. As a result, carbon fiber expands as temperatures go down.
This tendency effectively counterbalances the fact that the resin matrix used to bind together the fibers has a positive coefficient, essentially leading to a near-neutral overall coefficient.

The advantage in terms of cost falls clearly to the side of fiberglass. Producing long carbon fibers is far more a time-consuming and difficult process, which naturally makes carbon fiber more expensive.
Likewise, the broader range of uses for fiberglass — including non-protrusion products — helps to ensure that its price-point remains far more competitive.
Ultimately, both fiberglass and pultruded carbon fiber exhibit unique properties, and neither one is a clear winner for all applications.
Instead, you must carefully consider the needs and parameters of a given product in order to select the material best suited for your needs.