8.11 Foreign Object Impact on Composite Materials and the Modeling Challenges

Foreign object impact on composite materials continues to be an active field due to its importance in the design of load bearing composite aerostructures. The problem has been studied by many through the decades. Extensive experimental testing has been performed to characterize the impact damage and failure mechanisms. Advances in nondestructive inspection methods such as X-ray, CT scanning and high-quality ultrasound scanning has allowed for accurate and detailed measurements of impact damage. These advances have allowed to identify key mechanisms of damage events and subsequent local failure. The impacted specimens are subjected to compressive loading to assess the compressive strength after impact (CSAI) of the structure or coupon. The CSAI is an industry driven standard for evaluating the impact sensitivity of the structure. Theoretical and numerical models have been developed by many to predict the impact response as well as the damage extent. Steady advancements in computational power have resulted in an increase in numerical model developments for predicting both the impact event as well as the CSAI. This chapter focuses on the low-velocity impact of polymer matrix composites and the impact damage mechanisms. The focus will be set on identifying key failure mechanisms and the most recently developed mechanistic-based computational models. The differences between modeling techniques as well as the requirements needed to effectively capture the impact damage and response are discussed, including challenges that remain to be overcome.