The Extension of Crack Tip Damage Zones in Fiber Reinforced Plastic Laminates

Abstract

The size and character of the damage zone at the tip of sharp notches in fiber reinforced plastic laminates have been investigated. The variables studied were the stress intensity factor, specimen size, laminate thickness, ply thickness, ply orientation, and fiber properties. The damage zone consists of subcracks parallel to the fibers of each ply, in some cases accompanied by delamination between plies. The damage zone is found to increase in extent approximately in proportion to K² _I up to fracture for notch-sensitive laminates. For notch-insensitive laminates, a point is reached where the zone spreads rapidly across the entire specimen prior to fracture. A strong dependence of damage zone size and fracture toughness on ply thickness, fiber orientation, and fiber properties is demonstrated and discussed.