Sakhir runs put mileage on new-for-2015 drag-reduction system in Formula One's feeder series.
Japanese Formula Three Champion Nobuharu Matsushita has completed ART's driver line-up in GP2 for the 2015 season.
2013 British F3 champion joins forces with two-time GP2 champion squad.
GP3 champion Alex Lynn has joined Williams as the team's development driver, in addition to his already announced GP2 programme with DAMS.
Danish race winner replaces F1-bound Felipe Nasr to join Julian Leal in 2015.
Austrian set for third full season in Formula One feeder series.
Raffaele "Lello" Marciello won the 2013 European Formula 3 Championship and is part of the Ferrari Driver Academy.