An experimental study on low velocity impact performance of bolted composite joints part 1: Influence of halloysite nanotubes on dynamic loading response

Abstract

Mechanical joints are a widely utilized to assembly fiber reinforced polymer composites in marine applications. Impact is one of the most encountered unpredictable loading types which significantly diminishes the mechanical properties of structures. The goal of this study is to investigate the dynamic loading response of bolted basalt-epoxy composite laminates under different impact energies. Unlike the existing low velocity impact tests of bolted composite joints, to reveal the effect of localized impact damage, the low-velocity impact tests were conducted on two different regions as the top of bolt (ToB) and the side of washer (SoW). In addition, the effects of HNTs reinforcement on the impact response and the damage propagation were also evaluated. It was obtained that ToB damage was comparatively severe for the composite joints due to the propagation of the damage through the hole center. Moreover, HNTs improved the impact resistance about %15, especially at lower impact energies. However, the nanoreinforcement efficiency diminished with increasing impact energy levels. The obtained results were further supported with macro-size images and scanning electron microscopy (SEM). Together with Part II, this study reports an extensive work of impact tests of bolted composite joints utilized in the marine industry.