Ionic installs bower components (bower packages) into the project's lib folder:

www/lib 

This behaviour is defined in the projects .bowerrc file, which looks like this:

{
  "directory": "www/lib"
}

The project .bowerrc file may be found at the same level as the www folder.

Note that if you install angular-chart this way, you don't need to install Chart.js separately; it is one of the dependencies that bower will install for you. Of course, you must include the script tag that references the Chart.js file as usual!

Finally, if you want to link angular-chart.css you must follow the same procedure.