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Image processing methodology for assessment of drilling induced damage in CFRP
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Resumo(s)
Composite material components are produced in a near final shape. Machining operations
such as drilling are often indispensable, namely for joining of structures. This
process introduces damage along the periphery of the hole. Different methods to reduce
this induced damage were developed. However, difficulties arise when comparing them
since delamination is irregular in shape and in size. The delamination factor and the adjusted
delamination factor quantify the damage but none achieved full acceptance since
no international standards have been set. The aim of this work is to develop an image
processing methodology associated with digital radiography that is capable of assessing
the drilling induced damage in CFRP, being easily reproducible and allowing comparison
of different drilling approaches. The subtraction of pre and post drill radiographies
defined the target image to reach. In the image processing the threshold was found to be
the most influential variable causing significant changes to the delamination factors. A
new approach to the delamination factor is proposed in order to characterize the drilling
induced damage. This approach allows the minimization of the quantified damage for
the most irregular delamination shapes while equalling the current delamination factors
for regular (crown like) damages.
Descrição
Dissertação para obtenção do Grau de Mestre em
Engenharia Mecânica
Palavras-chave
Carbon fibre reinforced plastics Delamination NDT X-Radiography Image processing Threshold