Delamination of C/PEKK I-Beam using virtual crack closure technique and cohesive zone method

Greeshma Ramakrishna, Purdue University


A damage study is conducted on a carbon epoxy/PEKK (poly-ether-ketone-ketone) thermoplastic composite I-Beam, with a pre crack of 100 mm modeled between the top flange and the filler (butt joint between filler and web). This project is in collaboration with Fokker Aerostructures, Netherlands and is part of the Thermoplastic Primary Aircraft Structure innovation program (TAPAS). The C/PEKK I-Beam is modeled after a section of the Gulfstream G650 aircraft's centre beam, which was previously a carbon fiber/epoxy hat-stiffened skin construction. The objective of the thesis is to identify if the crack propagates in the I-Beam within the load range that act on the current centre beam of the G650 aircraft. Two finite element methods are identified to study the crack propagation in the model, namely virtual crack closure technique (VCCT) and the cohesive zone model (CZM). These two methods are verified by reproducing experimental data for calculating fracture toughness (mode I and mode II) of PEKK thermoplastic produced by CYTEC Inc, using ABAQUS CAE. Next, the I-Beam is modeled under a four point bending load, and analysis is performed using both the methods to study the loads at which the model begins to delaminate. Both the approaches produce similar data, verifying the results obtained. The model does delaminate within the range of the loads applied on the centre beam.




Tomar, Purdue University.

Subject Area

Aerospace engineering|Mechanical engineering|Materials science

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