The muscle fibers can be more worked if you Flex the worked muscle between sets. By doing this you increase blood flow to the required muscle and therefore increase the pump.
Flexing the muscle also increases the separation and the muscle in time will increase size and look more ripped.
Increasing the intensity in the workout by not letting the muscle rest the whole time between sets and thus intensifying the workout.
I suggest flexing for 5-10 seconds after each set and then after the final set I suggest you flex for between 30 seconds and 1 minute. This will fully fatigue the arm and force it into serious growth.
Trust me if you do this will make gains, always flex, the key is to make the muscle fill up with blood and increase the pump. The key to growth is the pump.
Add this simple thing to your workout and let me know how it goes.