In order to create a more efficient approach to design composite crash structures a new numerical method using the finite element codes PAM-CRASH and NASTRAN is presented. For the early design phase a simulation-based preliminary design method to dimension FRP crash structures is developed to allow automotive engineers to evaluate the key parameters and the structural performance of an energy absorbing structure. Based on an experimental database the global load level, structural stability and the energy absorption capabilities can be calculated for an arbitrary geometry. Since the method is based on implicit calculation it allows comparing and optimizing different concepts within an efficient time frame. A more detailed numerical study can be carried out using a new hybrid method representing the crushing characteristics of FRP in an explicit simulation. The technique is based on a coupled shell solid model, where a solid material is added to the shell elements. A composite shell model is used together with a ply damage and failure model to detect stability problems and fracture. In order to represent the crushing characteristics a solid material is used in the crushing region. Due to the hybrid approach appropriate material properties can be assigned to the corresponding sections. In the transition region the solids are constrained to the shell elements to guarantee that the resulting crushing forces are transmitted to the supporting structure. The relative position of the impacting wall is monitored by a contact search algorithm. This information is used to enable the crushing and transition model in vicinity of the impacting obstacle while the rest of the structure remains constant. The essential advantage is the efficient numerical implementation of the energy absorbing characteristic of composite material. Since a macroscopic model is used the time-step does not suffer due to stability issues. Thus simulations of complex car crash situations are realizable within an efficient time frame.
Simulation and dimensioning of energy absorbing composite structures for automotive applications
2011
12 Seiten, 12 Bilder, 11 Quellen
Conference paper
English
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