Evaluation of Laminar Defects in Fibre-Reinforced Beams

Lau Danny, Keng Shek (2004). Evaluation of Laminar Defects in Fibre-Reinforced Beams Honours Thesis, School of Engineering, The University of Queensland.

       
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Author Lau Danny, Keng Shek
Thesis Title Evaluation of Laminar Defects in Fibre-Reinforced Beams
School, Centre or Institute School of Engineering
Institution The University of Queensland
Publication date 2004
Thesis type Honours Thesis
Supervisor Martin Veidt
Total pages 87
Language eng
Subjects 0913 Mechanical Engineering
Formatted abstract
The structures of fiber-reinforced composite materials show that their mechanical property varies with different stacking sequences and have a variety of failure modes. One of the most common failures in composites materials is the growth of interlaminar cracks, also known as delamination.

Thus, the aim of this thesis is to investigate current methodologies used to investigate the integrity of the carbon fibre-reinforced composite beams with and without delamination. Vibration analysis is also introduced to determine its accuracy and capability in detecting laminar defects in beams.

Six test specimens (250 mm x 25 mm x 2 mm) with thirteen marked points were used for this thesis experiment. Half of them were undamaged beams and the other half were beams with created delamination around the center, and they were made with three different stacking sequences of 0° , ±45° and 90° configurations.

The ultrasonic pulser/receiver is chosen from the Non-Destructive Evaluation (NDE) technique for this thesis’ experimental assessment. The preliminary repeatability trials concluded that the ultrasonic technique is capable of detecting laminar defects in the specimens as well as determining the depth and length of the flaw.

The ultrasonic technique exploited here has proven to be effective in identifying damage regions in the beams, however this process is too time consuming. Therefore, further alternate experimental study was carried out base on vibration analysis. The laser vibrometer is used to give a better conclusion of the accuracy of using the ultrasonic
technique. Only one undamaged beam specimen was used and weights (brass) were later added for simulation of delamination in the beam. Two weights were used in the vibration analysis and the results had concluded that the laser vibrometer technique is capable of differentiating between an undamaged and a damaged beam in a short period of time. However the technique was unable to determine the depth and length of the simulated delamination, which the ultrasonic is capable of.
Keyword Fibre Reinforced Beam

Document type: Thesis
Collection: UQ Theses (non-RHD) - UQ staff and students only
 
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Created: Thu, 20 Nov 2014, 16:03:28 EST by Asma Asrar Qureshi on behalf of Scholarly Communication and Digitisation Service