PSI - Issue 25

Victor Rizov / Procedia Structural Integrity 25 (2020) 88–100 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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9

obtained for the two three-layered beam configurations is plotted against the non-dimensional time by using the rheological model reported in Fig. 1a (it should be noted that the time along the abscissa in Fig. 5 is presented in non-dimensional form by using the formula 1 1 /  t tE N  ).

1 2 / p p E E ratio (curve 1 – at

/ p E E 3

0.5 1

 p

Fig. 8. The strain energy release rate in non-dimensional form plotted against

, curve 2 –

/ p E E 3

/ p E E 3

1.0 1

2.0 1

 p

 p

at

and curve 3 - at

).

It is assumed that 0.5 3 1    . The curves in Fig. 5 indicate that the strain energy release rate in the beam configuration in which the delamination crack is located between layers 2 and 3 is higher than that in the beam with a delamination crack between layers 1 and 2. / 2 1  E E 0.5 , / 3 1  E E 0.7 , / 0.6 2 1    and /

0.5 2 1  E E , curve 2

Fig. 9. The strain energy release rate in non-dimensional form plotted against the non-dimensional time (curve 1 – at /

/ 1.0 2 1  E E and curve 3 – at

/ 2.0 2 1  E E ).

– at

One can observe also in Fig. 5 that the strain energy release rate increases with the time. The strain energy release rate at 0  t is caused by the instantaneous elastic strain that is modelled by the spring in the viscoelastic model shown in Fig. 1a.