"露出幸福的表情" 可以用英文表达为 "to show a happy expression" 或 "to have a happy expression on one's face".

来源：这个表达是由英文中的动词 "to show" 和形容词 "happy" 以及名词 "expression" 组成的。

英文例句及其中文翻译：

She showed a happy expression when she saw her family. 她看到家人时露出了幸福的表情。

He had a happy expression on his face when he received the good news. 他收到好消息时脸上露出幸福的表情。

The baby's happy expression made everyone in the room smile. 这个婴儿幸福的表情让房间里的每个人都笑了。