Virtual testing of composite structures: Progress and challenges in predicting damage, residual strength and crashworthiness

The entry into service of the Boeing 787 and the Airbus A350 XWB heralded a new era in the utilisation of carbon fibre composite material in the primary structure of passenger aircraft. With an estimated 20?% airframe weight reduction in comparison to equivalent conventional aluminium aircraft, commensurate savings in fuel consumption per revenue passenger kilometre, superior fatigue and corrosion resistance and the promise of reduced maintenance schedules for the operators, it is likely that these materials will continue to feature prominently in future aircraft development programmes. Nonetheless, these ‘all-composite’ aircraft have incurred high development costs which is not a sustainable business model if composites are to be exploited across the product range of airframe manufacturers, especially towards the smaller single-aisle passenger aircraft. The high costs of materials and tooling are exacerbated by slow production rates and the extensive level of physical testing required as part of the development and certification process.The increased use of simulation at all levels of the development cycle provides tremendous opportunities for reducing costs and improving production efficiencies. While the aerospace industry has been at the forefront of incorporating computational tools in the design and optimisation of aircraft, the use of composites has brought with it a new set of challenges in developing reliable and robust simulation tools. This chapter addresses the development and use of numerical modelling aimed at reducing the extent of physical testing. The ultimate objective is to enable certification by simulation which, in essence, requires the ability to reliably predict damage. This chapter will therefore focus on predicting damage initiation and propagation, the residual strength of damaged structures, and assessing the energy-absorbing capacity of composite structures for crashworthiness assessments. While the emphasis is primarily on aerostructures, the automotive and railway industries are exploring similar lightweighting strategies where issues such as crashworthiness are of paramount importance and where simulation will likewise play a prominent role.