No. Only one AudioBox can be used at one time. The AudioBox 1818 was designed and intended to function as the sole interface device.
You can connect other preamps like the D8 and the DP88 via ADAT connections to expand the channel count.
Only firewire devices like the FireStudio Project and the FireStudio Mobile can be chained together to increase channel count, but not indefinitely.
There are some ways that can allow for using multiple devices of any kind at the same time. PC uses ASIO4all drivers and Macs do so with creating Aggregate Devices. Either of these may get the job done, but may also incur many issues and stability will allows be a problem. Neither of these ways are officially supported or intended by manufacturers.
If you require more inputs, you will need to consider another interface that supports the number of inputs you need or may need.
