Measurement Methods for Fiber Volume Fraction of Fiber-Reinforced Polymer Composites

Fiber-reinforced composites are extensively utilized in mass-critical structures spanning aerospace, automotive, civil, etc., owing to their exceptional specific strength and stiffness. Fiber volume fraction (FVF) is a critical parameter for evaluating the performance of the composites. As a consequence, different measurement methods have been developed in recent decades, including resin removal method, thickness measurement method, microscopic method, etc. This paper reviews both traditional destructive (acid digestion, combustion, image analysis, etc.) and newly developed non-destructive techniques (X-ray CT, thermography, ultrasonic, XRD, eddy current, etc.), with a focus on their applicability to specific materials, measurement accuracy, operational complexity and cost. Moreover, key challenges and future directions are discussed, emphasizing the need for non-destructive testing, cost and energy efficiency, intelligent measurement and sustainability.