No, that shouldn’t be obvious.
First of all, the reason a bundle of hair is stronger and stiffer than a rod of equivalent area and material, is not necessarily applicable at the scale of 3D printing layers (there should be an effect, but it gets much more prevalent in smaller scales).
Then second, your example with the CFRP Sandwich Panel is not really correct. A full thickness CFRP plate is going to be stiffer and stronger than a Sandwich panel. Will it be much heavier and much more expensive? Yes! Will it be stiffer and stronger? Yes, a little bit. Only specific properties (so, per kg or per dollar) are improved (and by significant amount).
Also the core has to withstand out of plane shear in addition to compression and the bending stiffness is highly dependent on this shear stiffness.
My assumption for OPs effect is, that the criss-cross pattern is stiffer than the interlaminar shear stiffness of the individual 3D printed layers (but thats just a guess, could also be a quality aspect). This is not true for CFRP Sandwiches. CFRP interlaminar shear stiffness is much higher than of the core material (at least in general).
Sorry, don’t want to come across as an ass :)
No, that shouldn’t be obvious. First of all, the reason a bundle of hair is stronger and stiffer than a rod of equivalent area and material, is not necessarily applicable at the scale of 3D printing layers (there should be an effect, but it gets much more prevalent in smaller scales). Then second, your example with the CFRP Sandwich Panel is not really correct. A full thickness CFRP plate is going to be stiffer and stronger than a Sandwich panel. Will it be much heavier and much more expensive? Yes! Will it be stiffer and stronger? Yes, a little bit. Only specific properties (so, per kg or per dollar) are improved (and by significant amount). Also the core has to withstand out of plane shear in addition to compression and the bending stiffness is highly dependent on this shear stiffness. My assumption for OPs effect is, that the criss-cross pattern is stiffer than the interlaminar shear stiffness of the individual 3D printed layers (but thats just a guess, could also be a quality aspect). This is not true for CFRP Sandwiches. CFRP interlaminar shear stiffness is much higher than of the core material (at least in general). Sorry, don’t want to come across as an ass :)