The '~' is important: composites are in general very difficult to predict, and under compression even more so. (To build some intuition: carbon fibre, is just

The '~' is important: composites are in general very difficult to predict, and under compression even more so. (To build some intuition: carbon fibre, is just that, i.e. a fabric. No-one expects to be able to push on the edges of a sheet of fabric get any real resistance at all. If you then embed that it a plastic, i.e. make a composite, the plastic is mainly what makes it hold its shape. It's only really made stronger in tension by the fibers in it, why would you expect the compression to be better?)