PSI - Issue 13

Saeed Mousa et al. / Procedia Structural Integrity 13 (2018) 686–693 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

689

4

4.2. Peeling simulation Virtual-Crack-Closing-Technique VCCT is used in this work to simulate the debonding between the aluminum and brass. VCCT is based on fracture mechanics concepts. Fracture mechanics based methods have been successfully used for modelling initiation and propagation of debonding in sandwich of Al1100-brass-Al1100. In a fracture mechanics approach, propagation of debonding is assumed to initiate when the total energy release rate, G = G I + G II , is equal to the fracture energy, G c , associated with the current mode mixity. Here, G I is the energy release rate in mode I (opening), G II is the energy release rate in mode II (shearing) and the mode mixity is given by the fraction G II /G I . The fracture energy is determined experimentally for various mode mixity. The interaction type between the Al1100-brass Al1100 interfaces is assumed to be "Node to surface contact", and the bonding property between the two surfaces is failure criteria type "VCCT". 4.3. Model Verification To verify the present simulation, the comparison between the results obtained from FE model and the experimental results (presented in Figure 1) is shown in Figure 3. It is worth to note that, the contact area between of Al1100-brass Al1100 sandwich composites are 60 mm × 20 mm with. The peeling force increases by increasing the vertical displacement at Z axis, U z , in linear stage before approaching the peak value at which the peeling failure initiated. After that a rapid load drop appeared and then "saw tooth" load phenomenon is found in the numerical results as shown in the Figure 3. It can be seen that, a good agreement between the present numerical and the experimental results up to the maximum load. Therefore, the present simulation can be accepted in such engineering applications to predict the peeling load.

Figure 3: The comparison between the numerical results and experimental result at the same contact area .

5. Numerical Results 5.1. Preliminary study

In this section, a preliminary study is made to show the deboning growth rate of Al1100-brass-Al1100 sandwich composites. Furthermore, the effects of contact area and aluminum plate thickness on the peeling behavior of Al1100 brass-Al1100 sandwich composites are examined. Figure 4 illustrates the progressive peeling failure of Al1100-brass Al1100 sandwich composite. The picture in each case has been taken at different displacements at Z axis ( U z ). It can be seen that virtual crack of peeling test increases by increasing the U Z . Figure 5 illustrates the effect of Al strips thickness ( t al ) of Al-brass-Al sandwich composite on its peeling behavior. Five values of Al strips thickness ( t al ) varied from 0.2 mm to 0.7 mm by step 0.1 mm are taken. It can be seen that the maximum peeling force increases by increasing the values of t al as shown in FIGURE 6 (a). FIGURE6.b shows the relation between normalized peeling stress ( σ Peel / σ Peel, t0 ), initial value of t al = t o = 0.2 and Al thickness ratio ( t al ratio), t al /t o . Where peeling stress ( σ Peel ) equals P Peel divided by the tangent area (W x t al ). There is no effect of t al on σ Peel up to t al ratio equals 2, while, beyond this value σ Peel increased by increasing t al .