Session: 01-06-03: Impact, Fatigue, Damage and Fracture of Composite Structures 3

Paper Number: 162928

162928 - Prediction Model for the Effect of Low Velocity Impact on Double Hat Stiffened Skin Panels 

Carbon fiber reinforced polymer composites (CFRP) are easily susceptible to damage caused by low velocity impact (LVI). These impact events can occur during maintenance, transport, or in-service, and often lead to barely visible impact damage (BVID). The presence of BVID can have major consequences as it can lead to significant delamination between laminae or a significant decrease in compressive load carrying capacity. In aircraft skins, a popular composite structure is the use of hat-stiffeners to provide reinforcement to resist buckling. However, to implement these structures into aircraft, this requires subcomponent validation and testing to determine the strength and durability of these parts. One key area of interest is the effect of low-velocity impacts on the strength of the hat-stiffened panels, specifically the debonding between the hat and skin due to the impact event. Experimental testing of large hat stiffened panels for performance testing is expensive due to the size of the panels and it is not cost-effective to run numerous LVI experiments. Therefore, finite element analysis (FEA) can serve as a method to minimize the amount of experimental testing required to validate the design of the part.

This work presents a high fidelity model for predicting the sequence of damage and the resulting damage area for several damage modes such as delamination, fiber failure, and matrix failure within the double hat stiffened panel after it is subjected to low-velocity impact. To develop the prediction model for the LVI experiments, the geometry, materials, and boundary conditions were defined to match the experimental parameters set by the Air Force Research Laboratory (AFRL). These models will be tested under different impact conditions such as the impact energy and the location of the impactor along the panel. This model also explores the generation of a field function developed to determine the relationship between element length, cohesive strength, and debonding area. This will allow the selection and determination of appropriate element length and cohesive strength parameters to allow the predicted debonding area to improve its accuracy. Ultimately, the prediction models developed from this paper will be compared with experimental tests that are completed at the AFRL. The damaged states from this simulation will also be used to inform compression after impact simulations to investigate the effect of impact damage on the buckling and postbuckling response of hat stiffened panels.

Presenting Author: Eric Maravilla Arizona State University

Presenting Author Biography: Eric Maravilla is a PhD student at Arizona State University