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On the applicability of the mandrel peel test to characterize the fracture toughness of non-symmetric interfaces

Grafen, LN (2020) On the applicability of the mandrel peel test to characterize the fracture toughness of non-symmetric interfaces.

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Abstract:Delamination is one of the most detrimental damage modes in fiber reinforced composites. The resistance to delamination is characterized by the interlaminar fracture toughness, which is an important parameter used in the design of load-bearing composites structures. Most of the methods found in literature are designed to determine the delamination propagation of laminates where the crack propagates parallel between a symmetric or 0˚-0˚ interface. Since most structural composite products are multi-directional, these methods arguably leave little practical value. This research analyses the applicability of the mandrel peel test to measure the interlaminar fracture toughness of non-symmetric interfaces. For this purpose, carbon/PEEK specimen with a 0˚-θ˚ interface were manufactured and tested. The applicability of the mandrel peel setup to measure non-symmetric interfaces is quite favorable over for example the Double Cantilever Beam test, as the manufacturing of the specimen is relatively. Furthermore, the test procedure itself is rather simple and straightforward. It was found that the fracture toughness decreases with increasing fiber angle, but due to the high experimental scatter the significance of these findings are questionable. Furthermore, crack migration away from the intended interface and stick-slip behavior was encountered. The tendency of the crack to propagate away from the intended interface makes it difficult to relate the measured fracture toughness to the intended interlaminar fracture toughness. As such, this result means that the mandrel peel setup was not able to measure the delamination resistance of 0˚-θ˚ carbon/PEEK interfaces. The fracture behavior of carbon/PEEK material found in this study is similar to other studies and measurement methods, with crack propagation away from the intended interface is a common phenomenon. As the crack behavior is found the be similar among studies, it is recommended to test the method with a more brittle matrix material.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
Link to this item:http://purl.utwente.nl/essays/82700
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