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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a

b

c

Fig. 2. Compact specimen of composite laminates (a) and test with COD gauge (b) and axial extensometer (c).

For tests with DIC-system, specimens were prepared by making covering of black dots on white base (Fig. 3, a). The setup of equipment in test with DIC-system is shown on Fig. 3, b. DIC-system and test machine were synchronized by analog-digital converter (National Instruments USB 6251).

a

b

Fig. 3. Prepared compact specimen for test with DIC system (a) and test setup (b).

The constant displacement rate of moving grip equal to 1 mm/min was controlled by internal displacement sensor of the test system Instron 8801. In tests were collected data of load (kN) by internal load cell and crack opening displacement by COD gauge, extensometer and DIC-system. The tests were carried out in Center of experimental mechanics of Perm National Research Polytechnic University.

3. Test results

In the first part of work, the eccentric tension tests of compact specimens of glass-epoxy composite laminate with different measurement procedures of the crack opening displacement were provided. Loading curves in terms of axial load P (kN) and crack opening displacement u (mm) were obtained in tests and shown on Fig. 4 (a). Line 1 on Fig. 4 (a) corresponds to test with COD gauge, line 2 corresponds to test with axial extensometers and line 3 was plotted by DIC-system. It is important that after critical point, which corresponds to maximum load in test, the process of crack growth is stable. It is confirmed by realization the tests with unloading on the descending stage of loading curve. On Fig. 4 (b) the black line corresponds to the loading curve of tension test of compact specimen with two unloading on descending part of curve. Grey line on Fig. 4 (b) corresponds to initial loading curve of compact specimen without unloading.