Stolid

She was at a High School, at the inarticulate stage last time he was over, a round-eyed, pale-faced girl, with nothing of her mother in her, a silent stolid creature, who took it all as a matter of course, let her mother make a fuss of her, and then said "May I go now?"

Source: tatoeba (9593759)

His outlook on life, as with his habits were so stolid and plebeian.

Source: tatoeba (9951457)

He made no remark at first, but looked at her more than once—whether approvingly or not his stolid expression did not betray.

Source: tatoeba (12435003)

He went slowly to his tent and stretched himself on a blanket by the side of the snoring tall soldier. In the darkness he saw visions of a thousand-tongued fear that would babble at his back and cause him to flee, while others were going coolly about their country's business. He admitted that he would not be able to cope with this monster. He felt that every nerve in his body would be an ear to hear the voices, while other men would remain stolid and deaf.

Source: wiktionary