X-cor Sandwich Research Articles

Reference-free damage localization in time-space domain for structural health monitoring of X-COR sandwich composites

This article presents a guided wave based damage localization framework using a time-space analysis for structural health monitoring of X-COR sandwich composites with a reference-free perspective to overcome the difficulty in detecting reflected guided waves in a highly attenuated media. Transducers, including macro-fiber composites and piezoelectric wafers, are used to design the sensing paths. The time-space domain is constructed using de-noised signals that are processed by signal processing techniques including matching pursuit decomposition and Hilbert transform. The localization framework is then validated across a wide range of excitation frequencies in X-COR sandwich composites with seeded facesheet delamination. The results indicate that time-space analysis offers a high accuracy for detection and localization of internal damages and serves as a promising framework for structural health monitoring of complex sandwich composites with reinforcements. This work also provides a comprehensive study of the changes in group velocities, attenuation tendencies, and time-space resolution of actuated and converted modes under different excitation frequencies across a range of ultrasonic transducer sizes, thereby helping to improve reliability and accuracy of damage localization in time-space domain.

Multi-dimensional signal processing and mode tracking approach for guided wave based damage localization in X-COR sandwich composite

Abstract This paper presents a real-time signal processing and damage localization framework for ultrasonic guided wave based structural health monitoring of X-COR sandwich composites with a reference-free perspective. The high attenuation nature of X-COR composite significantly limits the ability to detect damage-induced reflected waveforms. Therefore, a novel multi-dimensional signal processing technique, coupled with a mode tracking approach for identifying trajectories and locating wave sources of all wave modes, including damage-induced converted modes, is proposed. The developed framework is experimentally validated using two internal damage scenarios: facesheet delamination and foam core separation. Results indicate that the framework offers not only high accuracy for locating internal damage positions, but also insights into guided wave propagation behaviors in highly complex composites such as the X-COR sandwich composite.

Study on the Tensile Strength in X-Cor Sandwich by Using Finite Element Method

In the tensile strength analysis, the failure criterion and materials stiffness degradation rule were proposed and the X-cor sandwich’s failure modes were also clarified. According to the failure criterion we used the elements with stiffness degradation and their distributions in the finite element model to simulate the types and propagation path of the failure and the failure mechanisms of X-cor sandwich were explained. The finite element analysis indicates during the tension firstly the interfaces between resin regions and Z-pin tips fail and the failure mode is Z-pin pull-out from the face-sheets. The finite element simulated results are in good agreement with the experimental results, the error range is -11.6%~9.7%. The comparison results show the failure criterion and stiffness degradation rule are reasonable and this method can be used to predict the X-cor sandwich’s tensile strength.

A New Method for Analyzing X-Cor Sandwich’s Shear Strength

The finite element software was used to get the X-cor sandwich’s shear strength. During the shear strength analysis, the failure criterion and materials stiffness degradation rules fitting for the analysis of X-cor sandwich’s failure mechanism were proposed and the X-cor sandwich’s failure process and modes were also clarified. According to the failure criterion we used the elements with stiffness degradation and their distributions in the finite element model to simulate the types and propagation path of the failure and the failure mechanisms of X-cor sandwich under shear were explained. The finite element analysis indicates during the shear firstly the resin regions fail and then the multiple failure modes of Z-pin pull-out from the face-sheet, Z-pin shear off and Z-pin buckling all exist. The propagation paths of the failure elements are dispersive. By contrasting the finite element results and test results the values are consistent well and the error range is -10.4%~7.4%. The comparison results show that the failure criterion and stiffness degradation rules are reasonable and this method can be used to predict the X-cor sandwich’s shear strength.

Finite Element Analysis of Tensile Modulus of X-Cor Sandwich

Through the analysis of micro-structures of Z-pin ends the basic hypothesis of elliptic configuration of the resin regions around Z-pin ends were proposed. The finite element model of the tensile modulus of X-cor sandwich was established and the finite element software ANSYS was used in the computation. The effects of Z-pin angle, diameter and density on the tensile modulus of X-cor sandwich were analyzed. Via the analysis of finite element model, the influencing trends of parameters of X-cor sandwich on the tensile modulus are achieved and the error range is ±10%. So the rationality of the proposed finite element model is verified and the finite element model can be used to forecast the tensile modulus of X-cor sandwich.

Finite Element Analysis of X-Cor Sandwich’s Shear Modulus

Through the observation of photomicrographs of resin regions around Z-pin ends, the basic hypothesis of the elliptic configuration of resin regions in the X-cor sandwich were proposed. The parametric equations for describing the microscopic structures of resin regions were given. Then the geometric analysis model of X-cor sandwich was established. The finite element software ANSYS was used to establish the finite element model of the shear modulus and the shear modulus was calculated. The error range of finite element analysis is between ±10%. So the rationality of finite element model is verified and the finite element model can be used to forecast the shear modulus.

Finite Element Analysis of X-Cor Sandwich's Compressive Strength

In this article the finite element software was used to analyse the values for compressive strength of X-cor sandwich. During the analysis, the failure criteria and materials stiffness degradation rules of failure mechanisms were proposed. The failure processes and failure modes were also clarified. In the finite element model we used the distributions of failure elements to simulate the failure processes. Meanwhile the failure mechanisms of X-cor sandwich were explained. The finite element analysis indicates that the resin regions of Z-pin tips fail firstly and the Z-pins fail secondly. The dominant failure mode is the Z-pin elastic buckling and the propagation paths of failure elements are dispersive. Through contrast the finite element values and test results are consistent well and the error range is -7.6%~9.5%. Therefore the failure criteria and stiffness degradation rules are reasonable and the model can be used to predict the compressive strength of X-cor sandwich.

Experimental Study on Mechanical Properties of X-Cor Sandwich

In this study, by changing Z-pin’s insertion parameters, the X-cor sandwich was prepared with vacuum curing molding process. The effects of Z-pin’s insertion angle, insertion density and diameter on compression, shear and tension properties were studied. The results show that Z-pin’s insertion parameters can significantly affect the mechanical properties of X-cor sandwich. The compression properties of X-cor sandwich are reduced, while shear properties are improved by the increase of Z-pin’s insertion angle. As Z-pin’s insertion angle increases the tension modulus increases while the tension strength firstly increases and secondly decreases. The mechanical properties increase with the increase of Z-pin’s insertion density and diameter. Compared with the foam core sandwich, the mechanical properties of X-cor sandwich are significantly improved in both modulus and strength.

Finite Element Analysis of X-Cor Sandwich’s Compressive Modulus

By contrasting the two finite models, a practical finite element computational model of X-cor sandwich’s compressive modulus was proposed. Through numerical analysis the X-cor sandwich’s stress field and compressive modulus were achieved and the effects of changing Z-pin’s radius, density, angle and volume fraction to the X-cor sandwich’s compressive modulus were analyzed. The numerical analysis results indicate that as the Z-pin’s angle increases the X-cor sandwich’s compressive modulus decreases, as the Z-pin’s radius, density and volume fraction increase the X-cor sandwich’s compressive modulus increases. Through the computation of finite model the influencing trends of X-cor sandwich’s parameters are achieved and the rationality of the proposed finite model is verified.

Research on Control System for the Automation Process of X-Cor Sandwich Structure Material

To realize the automation process for Pin implanting of X-cor sandwich structure, a hardware architecture of CNC based on open control system was proposed in which a Programmable Multi-axes Controller (PMAC) was adopted as the key unit for motion control and the accessory card for on-off control. The time based control mode is applied to realize synchronization of motion control and on-off control and to improve the real-time effort of the main tasks that closely related to the Pin implanting process. In addition, the device driver for PMAC, a user graphical interface as well as numerical control program interpretation module were also designed and the whole system is applied to the core material manufacturing process of X-cor sandwich structure.