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.
Impact damage of carbon fiber polymer-matrix composites, studied by electrical resistance measurement
Abstract Drop impact damage of continuous carbon fiber epoxy–matrix composite laminates, was studied by electrical resistance measurement, which was shown to be more sensitive than the ultrasonic method. The oblique resistance at an angle between the longitudinal and through-thickness directions was more effective than the surface longitudinal resistance in indicating damage, particularly interior damage. The oblique resistance values from longitudinal segments of a specimen were not additive, but the surface resistance values were. In the case of a unidirectional composite, electrical contacts at 45° from the longitudinal direction in the plane of the laminate were more effective than those at 90°. Even minor damage associated with negligible indentation was sensed. The spatial distribution of damage was also studied.
Finescaled piezoelectric 1–3 composites: properties and modeling
Abstract Composites consisting of fine, unidirectional ordered piezoelectric fibers in a polymer matrix offer a series of commercially relevant applications. Making use of PZT fibers with diameters in the range of 10–50 μm improved functional properties of such 1–3 composites are expected, stimulating the development of advanced ultrasonic transducers. The present paper reports on the preparation of 1–3 composites with different volume fractions of PZT(53/47) fibers and the characterization of their dielectric and piezoelectric properties. The experimental data were compared with results of finite element method modeling and parallel circuit modeling.