What is the difference between perpendicular and transverse loads? I saw this on a forum for 3d printing, but I couldn't find any online explanations on what the difference between both measures of loading was.
3D Printed objects are made of layers, and are intrinsically weaker in one direction, as you can 'pull the layers apart'. In this case 'transverse' means 'in the vertical direction as built', and 'perpendicular' means 'in any of the horizontal directions as built'.
The graph in question is with reference to infill patterns - these are generated in the slicer and can either be 2D (eg hexagonal tubes, the cross section is the same from one layer to the next) or 3D (eg cubes on their corners). This non-uniformity of the 2D patterns is why the patterns fail in compression (what the graph shows) differently according to the orientation. Imagine crushing a toilet roll tube from the top vs from the side.