PSI - Issue 5

Tretyakov M.P. et al. / Procedia Structural Integrity 5 (2017) 233–238 Tretyakov M.P./ Structural Integrity Procedia 00 (2017) 000 – 000

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Fig. 4. Loading curve of CT specimens (a), obtained by using COD gauge (1), axial extensometer (2) and DIC-system (3); loading curves (b) obtained in tests under monotonic tension (grey line) and tension with unloading (black line).

After analyzing the experimental data, the decision to use axial extensometer in the future tests was made. It corresponds to high load on composite specimen by pins of COD gauge because that gauge meant for steel CT specimens. Tests with using of DIC-system give information about not only crack opening displacement near the edge of specimen but also full displacement and strain field on the surface of specimen with notch and crack. However, the special procedure of specimen preparing is necessary. This test procedure is important for future studying of strain and displacement fields near the crack tip and studying of crack path. For studying the influence of stiffness of the loading system on the crack growth processes in glass-epoxy composite laminates, in the second part of the work, the compact specimens with different total length were manufactured. On the Fig. 5 the specimens with total length of 60 mm (a), 90 mm (b) and 120 mm (c) are shown. The notch geometry was the same for all specimens.

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Fig. 5. Specimens with total length of 60 mm (a), 90 mm (b) and 120 mm (c) for studying of influence of the loading system stiffness on the crack growth processes.

Loading curves in terms of axial load P (kN) and crack opening displacement u (mm) were obtained in tests for various stiffness of the loading system as shown on Fig. 6 for stiffness 12.5 kN/mm ( I ), 7.8 kN/mm ( II ), 6.3 kN/mm ( III ) with offset of 0.2 mm.