Wikia claims it is unknown at this point whether the barriers have a damage limit and I agree on this. There has been no proof yet of something that could damage the barriers. So as of writing (chapter 788) it would seem that the barrier would indeed be indestructible.
The strongest things we have seen the barrier block are:
- King Elizabello II's King punch, which could allegedly take down an entire fortress. (chapter 709)
- Hakuba's slashes (chapter 773)
- Gladius' full body rupture (chapter 773)
- The Birdcage (chapter 788)
- Chinjao's Haki imbued drill (chapter 788)
The only limitations we have seen so far are:
- It cannot block sound (chapter 742)
- It has a surface area limit (chapter 754 and 757)
- Only one barrier can be produced at the same time. (chapter 773)
As of now it does not seem like he would be able to block the slowbeam from Foxy, as that would consist of pure waves similar to sound or light. On the other hand, the beam from Franky would probably be blocked. Similar to King Elizabello II's King punch, it also seems that he would be able to block Whitebeard's shock wave.
Additionally, Oda has answered this question himself on the Volume 77, Chapter 773 SBS, saying Bartolomeo's barriers are indeed limited to one at the time and have a maximum capacity of 50.000 Bari-Bari or 500 Pickle-Pori-Pori-Bari-Bari's.
Reader: Oda-san, hello~. About Bartolomeo, he said something about how his barriers have a limit or whatever, so how many Bari-Bari's worth is its maximum capacity? P.N. Hoichael Jackson
Oda: Great question. There is in fact a limit to the space his barriers can cover, as well as how many barriers he can put up at a time. He can only hold up one barrier at a time, and they say that this one barrier can cover up to 50 thousand Bari-Bari's!! Amazing! 1 Bari-Bari equates to roughly 100x that of 1 Bori-Bari-Bari, so in other words, his barrier capacity is just about 500 Pickle-Pori-Pori-Bari-Bari's.
(Translator's Note: Bari, Bori, and Pori are all Japanese sound effects that roughly translate to 'crunching'.)