PSI - Issue 22

W. Zhang et al. / Procedia Structural Integrity 22 (2019) 251–258 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

257

7

A more specific expression is as equation (7):

     



G e 



1    f

, 0

0 ( )

c 

 

c

c c  





1

1       0 ( ) 0 ( ) f

0 , ,      t

,



f

0 C t 



(7)

0   

   



- G C t e  



1     f

c 

,

0 ( )

0 C t 



0

c

 

 

 

c

c

, , c c G V  are calculated values obtained from tests, which is convergent for the same batch of

parameters

6

1 mm s N   

1

=254.26

, N mm 

2.08 ,

0.4217 10 





.

G

mm C

specimens. In this paper,

c 





c

4. Model validation In Figure 13, the model predictions are compared to the testing data under different load levels and duration. Comparison are conducted after constant loading effect starting. The blue line shows the test data and the red line represent predictions of our proposed model. There exists some certain of error in the stress rising phase, and it is approximately the same when the stress reaches the maximum value. The decline phase after reaching the maximum is the failure phase of the cohesive area, which is not discussed. Six predictions of maximum strength has an average error of 1.22%. Overall, the two curves agree well, the modified model can give a satisfactory residual strength prediction result.

Fig. 13. Comparison of load-displacement curves with modified CZM and test results.

5. Conclusions and further work In this paper, a modified CZM considering degradation with constant load effect is proposed to evaluate the adhesive strength of sealing area, and calculation of the residual strength by load and time factors is obtained from ADTs. The modified model and the testing data are well matched. It is beneficial to solve the effect of applied load level on the real-time cohesive strength of the sealing area, which provides an important reference for evaluating the sealing life of the pouch cell. Then, the most service safety problems will be avoided in a large part. Based on current research, the following conclusions can be given: 1) An ADT is designed to simulate the separating process of the sealing area by using standard specimens on the in-situ tensile machine. The cohesive strength of the sealing area degrades under a small static tensile load and the sealing area fails gradually over a long period of time. A positive correlation is observed between the degradation rate and load. 2) A modified CZM considering degradation is proposed to describe the adhesive strength degradation curve and residual strength curve of the sealing area. The different strength degradation data are used for model validation. Good agreements can be seen between the testing data and model predictions.