Papers by Keyword: Z-PiN

Abstract: 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.

Abstract: The stitched composite T-joints and Z-pinned ones subject to bending load were investigated in this paper. A simple theoretical model characterizing the failure process of through the thickness reinforcement (TTR) during mode I delamination was presented. The experimental results showed that the initial damage load and maximum load of stitched specimens are higher than that of Z-pinned ones, while the energy absorption of stitched specimens during delamination is lower than that of Z-pinned ones. The energy absorption values predicted by the present model meet the experiments reasonably well. High friction force at the interface between TTR tow and matrix, with a long pull-out displacement of the tow, helps to improve the delamination resistance.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: Z-pins reinforced 2D ceramic matrix composites (CMCs), integratedly designed new materials, are developed to enhance 2D CMCs through-thickness in the form of Z-pins and to ensure significant increase in interlaminar fracture toughness, delamination resistance and impact resistance, and Z-pins reinforced 2D CMCs have much application. Finite element method was adopted to analyze stress distributions of Z-pins reinforced woven CMCs; the interlaminar shear tests were employed to measure interlaminar shear strength; fractographies were observed to examine failure mechanisms. The results are shown as the following: the insertion of Z-pins reduces concentrated stress fields and enhances the uniform stress distribution on the expected fracture plane. Interlaminar shear strength of Z-pins reinforced woven CMCs is increased as Z-pins insertion reaches a certain number. Interlaminar shear strength goes up with the rise of the number of inserted Z-pins. Z-pins shearing and fabric/matrix debonding are interlaminar failure mechanisms of Z-pins reinforced CMCs.

Abstract: Z-pins are thin fibrous composite or metallic rods that could increase the strength of laminated composites in the thickness direction. In this paper, three kinds of composite z-pins were made by improved pultrusion method. The length of pultrusion die is shortened to 30mm with no function of curing. The curing equipment is individual control drying ovens. And then, tensile properties of z-pins were reported as well as the appearance and fiber content. Results show that three kinds of z-pins have good flexural resilience. The fiber volume fraction is around 60%. Carbon fiber z-pin has smoother surface than aramid fiber z-pin. And, The thinner z-pin corresponds to the higher tensile strength and tensile modulus. The elongation rate of aramid fiber z-pin is greater than that of carbon fiber one.