If gravitational waves experience gravity, that means that gravitons don't just interact with the energy-carrying particles of the Standard Model, but there is a graviton-graviton interaction as well. Two different gravitational waves, in Einstein's relativity, should interfere when they meet.

Can gravitons be dark matter?

But on larger scales, the internal motions of individual galaxies indicate the presence of more mass than we observe. Galaxies in clusters move around too quickly, while X-rays reveal an insufficient amount of normal matter. ... Gravitons are undefined as is dark matter. We know dark matter has gravity.

Why havent we seen gravitons?

Individual gravitons interact very feebly, and we are only held to the planet because the Earth emits so many of them. Because a single graviton is so weak, it is impossible for us to directly detect individual classical gravitons.