Підвищення ефективності процесу свердління вуглепластиків та склопластиків лезовими алмазними свердлами

Dissertation for the degree of a candidate of technical sciences (doctor of philosophy)
in specialty 05.03.01 "Processes of mechanical processing, machine tools and tools" –
V. Bakul Institute for Superhard Materials NAS of Ukraine, Kyiv, 2019.
The actual scientific and technical goal of improving the efficiency of drilling holes in
CFRP and GFRP parts has been solved by increasing of tool life through using of diamond
drill bits and the decreasing of defect treatment by introducing a special drill bit design, the
cutting part of which has additional cutting edges and provides cutting on reverse of the
drilling.
A complex defect criterion (Q) is propoused. It makes possible to determinate the
defect of drilled hole at different areas of avoid and stratification, which may have a local
character or evenly spread around the hole edge. This is possible due to the first used model
of Kolding for predicting the stability of the drill during the processing of parts from carbon
fiber. It was established that the drilling of carbon fibers and fiberglass with diamond
drillings makes it possible to achieve 8 times the higher stability of the tool compared to
carbide drills, and the wear of diamond drills occurs evenly on the back and front surfaces,
and the carbide drills are much more intense on the rear surface leading to increase the
contact area of back and the treated surfaces, and as a result to increase the defect of the
openings. It was shown that reducing the defect of the aperture processing, namely, cutting
off the voidness and damaged layer of the hole surface, as well as extending the wear range,
which provides defective apertures at Q = 20 % – 25 %,, is due to the cutting processes in
the reverse of the drill, using developed diamond drill with a special design with auxiliary
cutting edges at an angle j1 = 0 °. It was established that the processing by diamond drillings
minimizes the thermodestruction of the hole from 0.50 mm to 0.03 mm in comparison with
the carbide drills and is accompanied by a reduction of the treatment temperature by
1.4 times in the processing of carbon sheet ((T = 41 – 49 °С) and 3 times in the processing
of fiberglass (T = 86 – 90 °С). It has been experimentally established that the phenomena of
contact interaction between the voidness of the drilled hole and the rotating drill characterize
the value of the uncut fibers. The obtained empirical relationships between the signal of
acoustic emission and the size of the voidness of the aperture allow to estimate the area of
the formed uncut fibers during the process of drilling of carbon fiber and fiberglass. A
diamond drill has been developed for efficient processing of holes in fibrous polymer
composite materials, which is equipped with two symmetrically-located diamond-carbide
plates. Developed practical recommendations for the use of developed diamond drills for
the efficient processing of parts from carbon fiber and fiberglass. The pilot-production
verification of the results of the dissertation work in the State Enterprise "Antonov" was
carried out, namely the application of the developed diamond drill for processing of
fiberglass and carbon fiber plastics allowed to increase the tool's stability in 3-5 times, to
obtain 2 times lower damages to the surface of the hole and to avoid thermal degradation of
the material being processed. in comparison with standard drill bits.