Despite strong shipment growth of 55% in the next year, Apple’s iPad is expected to face increased competition in 2012 with non-Apple tablet shipments forecast to grow 134%, according to a report by Digitimes.

Shipments of Android tablets are expected to more than double in 2012, helped by the launch of Google’s new Android operating system Ice Cream Sandwich. Android tablet shipments are expected to increase from around 20 million units in 2011 to 45 million units in 2012, while Apple’s iPad shipments are expected to rise from 35 million units to 55 million units in the next year.

The adoption of new tablet devices could be aided by the release of new ARM-based processors starting in the final quarter of 2011. The new processors, launched by Nvidia, Texas Instruments and Qualcomm, will provide tablet makers with new quad-core chips capable of generating increased display resolutions and enhanced 3D graphic processing capabilities.

Tablet shipments increased more than 420% from 2010 in the first six months of the year, with sales expected to increase into the second half to boost the number of shipments by 150% from a year earlier. Apple is expected to contribute more than 25.5 million iPad shipments in the second half of the year alone, up 76% compared to the first half of the year.

Apple has found itself in the unique position of being able to sell as many tablets as it ships, something its rivals have been unable to match. With some retailers unable to sell their remaining inventory, companies are holding back on tablet orders as they assess the demand for new tablet devices.