Apple recommends a set series of troubleshooting steps for recovering a bricked, unresponsive iPad. If you are unable to get the device working again, it may need to be professionally repaired or replaced -- contact your local Apple Store or Apple Support directly for advice. If you have a backup of the iPad on iTunes or iCloud, all of your apps, content and settings are safe.
Restart and Reset
Switch off the iPad by holding the Sleep/Wake button and then dragging the red slider across the screen, and then switch it back on by holding the Sleep/Wake button again. If the iPad does not respond to this process, try a reset, which is a more fundamental reboot of the device. Press and hold the Sleep/Wake button for at least 10 seconds until the Apple logo appears. If neither option works, move on to recharging or restoring the iPad.
Check that a low battery is not the cause of the problem by charging the iPad using the supplied USB cable and a mains adapter or your computer. If you have an alternative cable or power source to hand, switch to these to rule out a faulty cable or USB port as a potential problem. If the battery level is particularly low it may take up to five minutes for the charging symbol to appear on screen; it may be a further 20 minutes before the iPad has enough power to be able to start up.
Restoring an iPad returns it to its factory settings and erases all data from the device. Once the process has finished, you'll have the option to copy your apps and settings back onto the iPad using your most recent backup (you may be prompted to create a backup at the start of the restore process). To restore your iPad, connect it to your computer and open iTunes. Ensure you have the most recent version of iTunes installed, then choose the "Restore" option from the "Summary" tab. Follow the prompts on screen to wipe and reset your iPad.
If you have problems restoring your iPad, disconnect all other USB devices from your computer, and try connecting the iPad itself to a different port. Uninstalling and reinstalling the latest version of iTunes may help, as can applying the most recent updates for your operating system and security software. If the iPad remains bricked and unresponsive, then it's likely that it has developed a permanent fault.