PSI - Issue 22

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

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Fig. 1. Pouch cell in soft packaging.

Fig. 2. The illustration of specimen.

Fig. 3. The illustration of specimen installation. Fig. 4. In-situ tensile test system. 10 specimens were selected for test to obtain the load-displacement curves. The characteristics of the final fractures are different at different loading rate. In this study, only the cohesive failure of the heat-seal area was studied, shown as Figure 5(d), and results of other failure mode were removed from the cases to be analyzed, shown as Figure 5(a) 、 (b) 、 (c). Figure 6 shows the process of cohesive failure of heat-seal area. Figure 7 shows five groups of the load-displacement curves plotted by effective test data. There is a process of tensing the strip specimen before the sealing area starts deformation, and then the displacement increases with the increase of load. When the load increases to its critical value, the present adhesive area is not able to maintain its reliability. This critical value is the maximum load value in the load-displacement curve. After this critical point, the load drops with displacement continuing to increase. Eventually, the sealing adhesive structure completely fails. In the five groups of valid test results, the critical load values respectively are 45.37N, 45.93N, 45.56N, 45.49N, 44.97N and the average value is 45.46N, the corresponding displacements are 2.05mm, 2.16mm, 1.99mm, 2.38mm, 1.80mm and the average value is 2.08mm. Least squares fitting is used to fit the five sets of curves into a standard load-displacement curve, as shown in Figure 5. In the fitting relationship, the maximum load is 44.98N and the corresponding displacement is 2.01mm. The critical load average value of test results is greater than the value of the fitting curve with an error of 1.1%. And the corresponding displacement average value is greater than fitting value with an error of 3.4%.

Fig. 5. Different failure patterns: (a) fracture of film; (b) adhesive failure of CPP and AL; (c) fracture of the edge of heat-seal layer; (d) cohesive failure of heat-seal layer