It’s been along time since I did calculations like this so this could be well off !

I think I would start with the shear modulus of PVC which is 12-115 N/mm2. Let’s take worst case 115N/mm2

Multiply this by the shear area which is 2x(150x4.5)+2x(100x4.5)

This assumes a rectangular cookie cutter style blade pressing down with a female tool with the a hole in it supporting the underside of the area to be cut

This should give the shearing force I think. Try it and see !

Ps I don’t think the blade width comes into play so long as it can apply the force without bending or damage.

Happy to be corrected on the above!