From the NASA web site for Juno:
While other materials exist that make good radiation blockers, engineers chose titanium because lead is too soft to withstand the vibrations of launch, and some other materials were too difficult to work with.
There are harder and softer lead alloys, but nothing begins to approach titanium.
Later on the same page:
Your question is underspecified, but you might find something like TransHab (or other inflatable spacecraft designs) to fit the bill. There's already one such module attached to the ISS, so the principle appears to be entirely sound and practical.
From this older NASA page on TransHab, you can see that the membranes are made from layers of nextel ceramic ...