Abstract
There has been a growing interest in the last decade for the use of composite materials in the automotive industry, due to their low weight and high energy absorption capabilities. Predicting the response under impact conditions of these lightweight materials is crucial for both design and reduction of manufacturing and testing during the development of new vehicles. However, the complexity of composites makes it difficult to predict their behaviour using Finite Element Analysis (FEA). Hence, this research looks into the development of a reliable Finite Element methodology to simulate lightweight automotive crash structures, combining composite materials with polymeric foams in a sandwich panel. To achieve that goal, firstly a calibration process of a constitutive model for crushable foams was developed, including the proposed experimental tests to characterise the polymer. The approach was then validated by correlating a mixed-mode indentation tests with its corresponding Finite Element model and results from Digital Image Correlation (DIC). Secondly, different configurations of the crash structure were tested under mixed-mode loading conditions at quasi-static rates, based on the side-pole impact test. These experiments provided a better understanding with regard to the performance of each configuration. Furthermore, they were used to develop a robust FE methodology to accurately predict their behaviour, including good correlations in terms of load-displacement and failure mechanisms. Finally, the methodology was employed to design an impact test on a similar crash structure. The tests were conducted, and the outcomes were used to improve the Finite Element models, showing good agreement in terms of loads and energy absorption capability. It was found that the structures that were tested did not experience composite crushing, highlighting the need of further optimisation of the sandwich structure. Therefore, having validated the numerical methodology, FEA can now be used to assess the influence of different design approaches to improve the performance of this type of crash structures, prior to the manufacturing and testing of new full-size components.