PSI - Issue 61

T. Stoel et al. / Procedia Structural Integrity 61 (2024) 206–213

211

6

T. Stoel et al. / Structural Integrity Procedia 00 (2023) 000 – 000

ensure a fast increase of the respective process force as well as a nearly constant force during the process with neglectable oscillation: = −1 ± ∙ | set − R set | (2) The values for the displacement increments were determined empirically. The usage of too large values still leads to a non-negligible oscillation, whereas small values lead to a delay in force buildup. Finally, the described closed control loop was implemented as a VUAMP subroutine. For a reduction of computational time, a mass scaling factor of ms = 100 was used. It was ensured that the ratio of kinetic and total internal energy of the whole model remained below 1 % to inhibit any artificial inertia effects on the process model. 3. Results and discussion The developed CFRP near-net-shape blanking model was used to determine the blanking force for different values of fiber volume fraction, fiber orientation relative to the cutting line as well as blank holder force and counter force (see Figure 1). In the following, the development of the blanking force in dependence of the blanking path b until laminate failure realized by element deletion ( ft = 0.97) for different material and process parameters is analyzed. Figure 3a shows the development of the blanking force in dependence of the blanking path for different fiber orientations relative to the cutting line. It is shown that the blanking force at laminate failure is increasing if the fiber orientation on one of the two sides of the cutting line approaches a perpendicular orientation relative to the cutting line. Therefore, the highest blanking force can be seen for the fiber orientation of 1,2 = {0 ° , 90 ° }. Furthermore, it can be noted that the blanking path at laminate failure occurs earliest with a fiber orientation of 1,2 = {0 ° , 90 ° }.

b = 0.1 mm

(a)

(b)

f = 60 % b = 45 mm/s BH− / CP− f /

10 15 20 25 30 35 40 45 50 55 60 65 10 15 20 25 30 35 40 45 50 55 60 65 70 75

von Mises stress 800

1,2 = {22.5 ° , 67.5 ° } 1,2 = {45 ° , 45 ° } 1,2 = {0 ° , 90 ° }

/MPa

Blanking force B / kN

400

1,2 = {22.5 ° , 67.5 ° } 1,2 = {45 ° , 45 ° } 1,2 = {0 ° , 90 ° } ° ° ° °

fiber orientation

0

0 5

Blanking path b / mm

0.00 0.05 0.10 0.15 0.20 0.25 0.30

Figure 3: Development of the blanking force in dependence of the blanking path different fiber orientations (a) and distribution of the von Mises stress for different fiber orientations (b)

The development of the blanking forces in Figure 3a indicates a nonlinear relation between blanking force and fiber orientation. Hence, the utilized cutting line can be seen as a superposition of two single fiber orientations with a superior impact of the perpendicular fiber orientation. Figure 3b shows the von Mises stress in the laminate for