In an online class, can I use materials in more than one class session or more than once in a semester?
The answer is most likely yes under the TEACH Act. You can use a copyrighted material if properly linked and attributed for more than one lesson. For example, you teach a lesson with an article for a week period in August, then close access to it. Later, say, in December, you can use the article again to teach new material with it, or to reinforce a point or lesson from earlier.