APPLICATION AND POTENTIAL OF EMERGING NDE-METHODS FOR CARBON FIBER REINFORCED COMPOSITES

摘要

Carbon fibre laminates become increasingly important in aircraft and automotive industry due to their weight specific mechanical performance. New developments based on textile preform technologies offer a high potential for further improvements and cost savings. These textile materials need to be qualified by non-destructive evaluation methods. Potential defects may have their origin either in the production process or in circumstances occurring later on when the component is being used (ageing, impacts, etc.). This paper deals mainly with the first type and investigates which defects caused by imperfect fabrication are detectable and how they can be displayed. For this purpose five carbon reinforced composite plates based on non-crimp-fabrics with different thicknesses were produced. The plates contain many artificial defects which may occur also in real mass-production processes, e.g. inclusion of liquids like grease, glue, form release or cleaning agents but also inclusions of solid materials like adhesive tapes or foils or a small part of a cardboard cutter. The samples were tested with modern acoustic and thermographic methods recently developed at IKP. Acoustical methods like non-linear vibrometry and air-coupled ultrasound were used as well as lock in thermography with optical and ultrasound excitation. The results obtained with the different NDE-methods were compared with respect to their defect information and their benefits for defect detection and imaging.