Using Thermogravimetric Analysis to Determine Carbon Fiber Weight Percentage of Fiber-Reinforced Plastics

The fiber content φ of fiber-reinforced plastics (FRPs) is a dominant influence on the mechanical performance and is therefore an essential quality measure. There is a lack of cost-efficient but precise measurement methods to determine φ of randomly distributed long-carbon-fiber-reinforced materials. Macro thermogravimetric analysis (TGA) is widely used for glass-fiber-reinforced plastics (GFRPs) as it is less labor-intense than sulfuric acid digestion. However, this method is not standardized for carbon-fiber-reinforced plastics (CFRPs). In this study, several macro TGA measurements of raw materials and FRPs were performed to measure degradation in relation to temperature, time and atmosphere. Conditions were found and validated which degraded the polymer but not the carbon fiber. Using macro TGA, it is possible to measure φ of a CFRP with an absolute error of less than 0.5 wt% compared to the actual value measured by weighing the raw materials.