Investigation of intelligent features for CFRP structure in automotive safety systems
New stringent European Union regulations, on both emission and fuel consumption are driving the automobile manufacturers in continuous search of suitable lightweight materials. Carbon Fiber Reinforced Plastic (CFRP) is one of the most prominent lightweight materials in use. In addition to the benefit of reduction in weight, the inherent properties of CFRP materials such as acoustic emission, electrical properties of fibers etc. change with the applied load during elastic deformation and failure. This change in properties is the base of the presented idea to assign intelligence to current automotive safety structures made from CFRP material. This paper gives a short review of the work done by various researchers in the field of health monitoring of CFRP structures using electrical resistance. Further, experiments were performed for initial investigations to show the promising usage of the above explained intelligence features. Tube-like and plate-like specimens were used, because of their similarity with automotive structures. It can be concluded, that the mechanisms like elastic bending and micro buckling have very negligible influence on resistance change compared to other mechanisms. The results from the experiments show significant resistance change within 5 to 50 milliseconds after impact. This demonstrates the potential of this concept to be used for crash severity detection in automobiles.
Energetic analysis of fragmentation mechanisms and dynamic delamination modelling in CFRP composites
This paper deals with the understanding and the numerical simulation of complex dissipative phenomena involved in composite absorbers for two main degradation modes: the fragmentation and the delamination modes. Fragmentation is the last step of degradation in pure compression leading to total failure of a laminate and for CFRP it is mainly initiated by a microbuckling mechanism, which is dependant on the microstructural imperfections. The dissipated energies associated to the fragment creation are evaluated through micromodelling approaches and contrary to expectations, these energies seem to be insensitive to microscopic parameters. A Weibull density knowledge on peak load and dissipated energy is also proposed. On the other hand, computation control on the delamination process has been investigated. Numerical sensitivities are justified, thanks to analytical approaches and physical-based mesh criteria are proposed for classical propagation tests. Some quasi-static experiments have been performed and good accuracy is obtained with the model. All these results give perspectives to implement delamination and fragmentation interactions at mesoscale within an absorber-like configuration.
OPTIMAL TRIGGERING OF AN AIRBAG
This paper describes how to determine the optimal triggering timing of an airbag and presents a new and straightforward algorithm based upon the concept of prediction. The optimal timing is determined by estimating and predicting the motion of the occupant after collision by using a model of the occupant. The authors introduce the one-mass model to describe the occupant's motion after collision. Observation of the motion of the occupant rather than the crashing automobile makes the problem straightforward.