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.
On the detection of vehicular crashes-system characteristics and architecture
Safety systems for ground vehicles are deployed in different phases according to the timing of activation relative to the occurrence instant of an accident. Collision warning or avoidance systems function prior to an accident, while occupant protection systems act during a collision to mitigate the damage or injuries caused by an accident. This paper deals with crash sensing systems that detect a collision and evaluate the severity of a crash. One major application of these sensing systems is their current use in occupant restraint systems. They may also be utilized in the future for advanced vehicle control and safety systems. With air bags becoming standard equipment in new passenger vehicles, crash sensing technologies have advanced considerably. Yet, existing challenges and new innovations continue to demand improvements in their functions. This paper focuses on the system performance of crash sensing systems. The purpose of this paper is to propose a framework of addressing various design issues from both a component level and a system perspective. Through the discussions of crash data analysis, the design concepts of crash sensors are highlighted. The characteristics of representative mechanical and electronic sensors are analyzed and the guidelines of sensor selection to meet design requirements are discussed. Also, an assessment of sensor reliability is reviewed with various system architectures. Finally, suggestions are made to enhance system performance in areas that may benefit from the addition of sensing functionality. The public has become conscientiously aware of the importance of transportation safety. With more advanced technologies introduced into ground vehicles, the safety concerns will intensify. The demand for a friendly driving environment and vehicle interior will further promote the requirements of vehicular safety systems. Crash sensing will remain a challenging and active area for years to come.
Experimental study on bond behavior between high-strength grout and deformed steel bars
Abstract Engineers use high-strength grout to connect precast concrete members for its low shrinkage and good fluidity. This paper designed 87 central pull-out specimens using the control variable method to investigate the influence of factors on the rebar-grout bond property such as compressive strength, steel grade, bar diameter, transverse stirrups, and bond length. The test result showed that improving grout compressive strength (85.8 MPa–122.7 MPa) cannot improve the bond strength, which was different from the previous conclusions of concrete pull-out tests. Simplified formulas were presented for calculating the characteristic values of bond strength, residual strength, peak slip, and relative slip of load-holding platform based on parameter analysis. Then, a constitutive model was proposed to predict the full-range bond stress-slip curve of high-strength grout and steel bar specimens from bearing to failure. Finally, FEA models were established to evaluate the applicability and accuracy of the constitutive model.