Examination and modification of equivalent delamination factor for assessment of high speed drilling

Composite components suffer delamination at the entrance and exit of drilled holes. Many measures have been suggested by different researchers to assess such delamination damage. These include delamination factor, two-dimensional delamination factor, damage ratio, adjusted delamination factor, refined delamination factor, equivalent delamination factor, and minimum delamination factor. Among all these various assessment factors, the equivalent delamination factor looks simple and able to take into account the different features of delamination. However, the method of calculation of the equivalent delamination factor may not provide accurate values for delamination resulting from high speed drilling. The aim of this paper is to evaluate the equivalent delamination factor in high speed drilling of a composite laminate using a twist drill and develop a new approach to determine equivalent delamination factor which can be used for both conventional and high speed drilling conditions. This new method is applied to calculate the equivalent delamination factor in trials of drilling composite specimens at different speeds and feed rates and is found suitable.