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Abstract
Structural response of composite structures subjected to different impact loadings is studied. The low-velocity and high-velocity ballistic impacts, and residual structural response are analysed. First, low-velocity impact response of the composite laminates and composite sandwich panels are investigated. The composite honeycomb sandwich panels are composed of facesheets made of carbon fibre reinforced facesheets and the Nomex honeycomb core. Composite laminates and sandwich panels are subjected to six different impact tests performed with impact energy levels ranging from 17.13 to 154.18 J. Two types of loading conditions have been implemented: (a) impacts by the impactors having the same mass and variable impact velocities resulting in different impact energy levels; (b) impacts with the same level of energy (equivalent energy impacts) and different impactor masses with corresponding (different) velocities. The experiments probed the effects of impactor mass, velocity, and different impact energy levels by analysing the patterns of induced damage, energy absorption, penetration resistance and force-displacement response. Microscopic non-intrusive damage assessment procedures have been employed to investigate various damage modes induced by the drop weight impact depending on the impact of velocities and impactor masses.
Also, ballistic damage effects on the structural performance of composite honeycomb sandwich panels are investigated. Ballistic tests have been conducted in a shooting range using live projectiles of three different calibres. The sample panels are subjected to normal, oblique, and multiple oblique impacts to simulate the damage to composite sandwich structures that can be inflicted by the use of small weapons or by fragments of anti-aircraft ammunition. The modes and extent of the damage induced have been analysed using optical microscopy, X-ray inspections, and computer tomography methods. Structural performance of the intact and ballistically damaged panels has been investigated experimentally: using in-plane compression tests, and numerically, based on the finite-element modelling and analysis. The reduction in the load-carrying ability caused by the ballistic damage has been assessed for the panels under consideration and compared with that predicted by numerical simulations.