Melbourne VIC, Australia, 23 January 2015 | AAP

Samantha Stosur has joined the Aussie women’s exit from the Open with a straight sets loss to big-serving American Coco Vandeweghe.

Stosur’s run at Melbourne Park ended in the same fashion as Casey Dellacqua and Ajla Tomljanovic, who were also second-round losers.

She fell to Vandeweghe 6-4 6-4, leaving no local hopes standing in the women’s singles.

Dellacqua went down to Madison Keys while Brisbane-based import Tomljanovic bowed out of the Open earlier on Thursday with 6-1 7-6 (7-1) loss to another American Varvara Lepchenko.

Vandeweghe lived up to her billing as one of the best servers in the women’s game, with 20th seed Stosur unable to break her.

The world No.37 sent down 11 aces with her serve reaching 195km/h.

It continued a run of disappointments for the Queenslander at the Open with her best result in six years a fourth-round showing in 2010.

The former US Open champion didn’t enter the tournament in sparkling form after losing in the first round in Brisbane and second round in Sydney.

Vandeweghe will next take on another American in Madison Brengle.

It’s her first ever appearance in a grand slam third round.