Are abrasions considered closed wounds?
The definition of closed and open wounds is variable. In histopathological terms (i.e. looking under a microscope) it is usually defined that a wound where the dermis is affected is open. In this case an abrasion is an open wound. This puts it in the same class as cuts (incisional/lacerations), tears and punctures. Closed wounds on the other hand are when the dermis isn't affected, such as in a haematoma (blood collection under the skin) or crush injury (extreme force typically for a long period of time) and contusions (i.e. bruises). 

Medically they may be divided by management. Where open wounds are wounds which are likely to be contaminated and need thorough cleaning and may need antibiotic cover whereas closed wounds are ones that are very unlikely to be. In this case, abrasions may be considered a relatively closed wound as not all the protective layers of the skin have been breached (the dermis is not completely breached). Thus the physical barriers are relatively intact and continue to offer us defense against bacteria and organisms.