دانلود رایگان مقاله انگلیسی بهبود مقاومت سنسور فیبر نوری مبتنی بر تجزیه و تحلیل انتقال کششی - الزویر 2018

ABSTRACT

To realize the reliable and long-term strain detection, the durability of optical fiber sensors has attracted more and more attention. The packaging technique has been considered as an effective method, which can enhance the survival ratios of optical fiber sensors to resist the harsh construction and service environment in civil engineering. To monitor the internal strain of structures, the embedded installation is adopted. Due to the different material properties between host material and the protective layer, the monitored structure embedded with sensors can be regarded as a typical model containing inclusions. Interfacial characteristic between the sensor and host material exists obviously, and the contacted interface is prone to debonding failure induced by the large interfacial shear stress. To recognize the local interfacial debonding damage and extend the effective life cycle of the embedded sensor, strain transfer analysis of a general three-layered sensing model is conducted to investigate the failure mechanism. The perturbation of the embedded sensor on the local strain field of host material is discussed. Based on the theoretical analysis, the distribution of the interfacial shear stress along the sensing length is characterized and adopted for the diagnosis of local interfacial debonding, and the sensitive parameters influencing the interfacial shear stress are also investigated. The research in this paper explores the interfacial debonding failure mechanism of embedded sensors based on the strain transfer analysis and provides theoretical basis for enhancing the interfacial bonding properties and improving the durability of embedded optical fiber sensors.

7. Conclusions

It is well known that the uncoordinated deformation induced by the mismatch of material properties of each layer in a multi-layered structure is prone to interfacial debonding failure between the adjacent layers under the external loading. For the commonly used sensing model, the interface between the monitored structure and the embedded sensor is also vulnerable to interfacial damage. To enhance the interfacial bonding properties and guarantee the relatively long-term effective measurement, theoretical approach based on the strain transfer analysis is performed and the following conclusions can be drawn from the study:

(1) The perturbation of the embedded sensor on the strain field of the host material can be assessed by the overlapped degree of Eqs. (12) and (13), which can be used to determine the maximum radius of the protective layer.

(2) Eq. (14) can be used to diagnose the occurrence of local interfacial debonding between the sensor and host material, and the related strain transfer error modification of the model with influence of local interfacial debonding considered follows Eq. (17). The local interfacial debonding decreases the strain transfer ratio and enough interfacial bonding strength should be guaranteed, especially at the bonded-length ends of the multi-layered sensing model.

(3) To prevent the local interfacial debonding between the embedded sensor and host material and enhance the effective measurement of the sensor, the thicker protective layer with relatively lower modulus and the longer gauge length are suggested in the application design. When the embedded sensor is employed to detect the strain of host material with low modulus, the interfacial debonding should be carefully considered by the proposed strain transfer theory.