AbstractThe present work focuses on the applicability of the mandrel peel test to quantify the fracture toughness of woven fabric Carbon/PEEK composites. For this purpose, the mandrel peel test was compared to the standardized DCB test. Unstable crack propagation (stick-slip) was observed in both testing techniques. Nevertheless, each time unstable crack propagation occurs it is arrested by the mandrel. As a result more crack re-initiations were observed per unit crack length. This effect is expected to increase the statistical relevance of a single test and thereby increases the reliability of the test. As an additional advantage the mandrel peel test is very easy to perform compared to the DCB test. The crosshead speed and the peel arm width were varied in this study to obtain the influence of these variables on the test results. Fractographic investigations were performed to study the nature of the crack propagation for the two different testing techniques.