EXPERIMENTAL AND NUMERICAL STUDY FOR HAT-STIFFENER SEPARATION DURING LOW VELOCITY IMPACT

Abstract

Barely Visible Impact Damage (BVID) is known to be a potential hazard to composite structures which are prevalent in the aerospace industry. Low Velocity Impact (LVI) events can cause composite structures to undergo large deformations and experience delamination between laminae which reduces their compression load carrying capability. Understanding the driving factors for this damage event is essential for safe design of composite structures. Physical experiments on complex composite structures are expensive and there is a constant effort in the industry to develop accurate numeric models that capture delamination events. In addition to LVI events that cause interlaminar delamination, it is also important to study the failure that occurs between composite structures that are bonded together. In this study, the interface delamination between a hat stiffener and a composite skin coupon under impact loading will be investigated. The hat stiffener and skin are made of IM7/977-3 material and are co-cured during the manufacturing process. The goal of the experiments is to understand the method in which debonding occurs in a physical sense to assist numerical modeling efforts. Dynamic tests are compared to static tests to observe the effect of force oscillations during the experiment. A finite element model was developed to recreate both static and dynamic experiments. The numerical model serves to provide additional insights regarding the failure events occurring in the hat stiffened coupon.