Carbon Fiber vs Fiberglass:

 Though carbon fiber and fiberglass share some similar attributes and are used interchangeably in a handful of different industrial and everyday applications, the two materials are vastly different from one another.

For instance…
Strength:
Though either material is substantially stronger than steel, industrial carbon fiber is more than 20 percent stronger than the best fiberglass. Carbon fiber boasts a strength-to-weight ratio roughly twice that of fiberglass.

Stiffness:
Carbon fiber is significantly less flexible than fiberglass and is the preferred material for applications in which stiffness and rigidity are essential (mechanical components for example). Carbon fiber tensile modulus is 4 times that of fiberglass. For applications in which flexibility is required or rigidity isn’t imperative, fiberglass is often the preferred choice. 

Weight:
Compared to metals like steel and aluminum, both carbon fiber and fiberglass materials are remarkably light in the weight given their inherent strength. In environments and applications in which minimal weight is imperative (aerospace or car racing, for example) both materials are in high demand and used quite frequently. Typically, however, carbon fiber weighs about 15% less than fiberglass composites. 

Thermal Expansion:
Unlike most materials, carbon fiber has a negative coefficient of thermal expansion which means that the material in its purest form actually expands in cold temperatures. However, the matrix in carbon fiber carries a positive coefficient of thermal expansion and the two typically offset one another for an overall coefficient of thermal expansion close to neutral. This is a fancy way of saying that carbon fiber materials do not contract in cold temperatures while fiberglass products may. So if extreme heat or cold is a factor, and thermal expansion is a concern, carbon fiber may be the better way to go.
Corrosion Resistance
If your carbon fiber or fiberglass application will be exposed to harmful chemicals, acids, or abrasive environments, you’ll be happy to learn that either material is highly resistant to corrosion or chemical abrasions. 

Cost:
Generally, fiberglass components are viewed as more cost-effective as compared to their carbon fiber counterparts. This is due in large part to the fact that fiberglass is used in a wider range of applications and manufacturing costs are significantly lower. Carbon fiber manufacturing is a much more involved process and there are fewer established manufacturers in the industry.