PSI - Issue 61

212 T. Stoel et al. / Procedia Structural Integrity 61 (2024) 206–213 T. Stoel et al. / Structural Integrity Procedia 00 (2019) 000 – 000 7 different fiber orientations at b = 0.1 mm. It is to be noted that for 1,2 = {0 ° , 90 ° }, where the fibers lie perpendicular to the cutting line, increased von Mises stresses predominantly occur at the top of the laminate clamped by the blank holder and on the bottom side of the laminate clamped by the counter punch. For the parallel orientation of the fibers to the cutting line, von Mises stresses predominantly occur in the shear zone and do not stretch along the laminate surface. An equal distribution of von Mises stresses for both sides of the cutting line can be seen for 1,2 = {45 ° , 45 ° }. This suggests that the distribution of von Mises stresses is controlled by the fiber orientation. Figure 4a shows the development of the blanking force in dependence of the blanking path b for different fiber volume fractions and fiber orientations. It is shown that the maximum blanking force increases with an increase in fiber volume fraction, even though the influence is smaller for 1,2 = {0 ° , 90 ° }. The increase in blanking force needed to trigger element deletion at ft = 0.97 and thus for the laminate to fail can be explained by the overall higher strength of the laminate with f = 70 % (see Table 1).

(a)

(b)

b = 45 mm/s f = 60 %

b = 45 mm/s BH− / CP−

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

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

Blanking force B / kN

Blanking force B / kN

Blanking path b / mm f = 60 % f = 70 % 1,2 = {0 ° , 90 ° } 1,2 = {45 ° , 45 ° } 1,2

Blanking path b / mm BH− CP− BH+ CP+ 1,2 = {0 ° , 90 ° } 1,2 = {45 ° , 45 ° }

= {22.5 ° , 67.5 ° }

0 5

0 5

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40

0.00 0.05 0.10 0.15 0.20 0.25 0.30

Figure 4: Development of the blanking force in dependence of the blanking path for different fiber orientations, fiber volume fractions (a), and process forces (b)

For all three different fiber orientations, the blanking path at which the laminate fails is lower for a fiber volume fraction of 70 % than for a fiber volume fraction of 60 %, which resembles an increasingly brittle material behavior. The development of the blanking force in dependence of the blanking path for two levels of blank holder and counter force as well as two different fiber orientation is shown in Figure 4b. For both fiber orientations, an increase in blank holder and counter force results in a higher blanking force at laminate failure. This effect is significantly more pronounced with a fiber orientation of 1,2 = {45 ° , 45 ° } than with a fiber orientation of 1,2 = {0 ° , 90 ° }. In addition, a delay of laminate failure can be seen for a fiber orientation of 1,2 = {45 ° , 45 ° } due to higher blank holder and counter force. A possible explanation for the increase in blanking force is a higher induction of compressive stresses by means of blank holder and counter punch, and therefore a suppression of the fiber tension damage mode which determines element deletion. 4. Conclusion and outlook A numerical model for shearing of unidirectional carbon fiber reinforced plastic laminates by means of near-net shape blanking was developed and the effects of a variation of fiber volume fraction, fiber orientation and process forces on the blanking force at laminate failure were investigated. It was shown that the blanking force at laminate