Crack Detecting by Carbon Fiber Polymer-Matrix Layer

2011 ◽  
Vol 52-54 ◽  
pp. 1747-1751
Author(s):  
Xi Fang ◽  
Zhuo Qiu Li ◽  
Si Rong Zhu ◽  
Yong Lv
Keyword(s):  
Carbon Fiber ◽  
Uniaxial Tension ◽  
Polymer Matrix ◽  
Bending Test ◽  
Functional Material ◽  
Fiber Layer ◽  
Resistance Change ◽  
Matrix Layer ◽  
Sensing Application ◽  
Embedded Crack

Carbon fiber (CF) is an essential functional material focused on widely, especially in civil engineering. The mechano-electric character of carbon fiber layer based on the polymer-matrix and its sensing application to the pre-embedded crack detecting were experimentally discussed in this paper. Through the uniaxial tension the CF layer reveals a good performance by resistance changing with response to the loading. By three-points bending test, the crack of the structure would lead to an evident increasing of the resistance change ratio of CF layer. From the experimental results, the ratio of resistance increasing of CF layer laid on crack will be higher by 14.25% in average than that of CF layer with no crack laid. Thus carbon fiber mat composed with polymer will provides a new kind of potential sensor which can detect the defects of the structure.

Resistance Responses of Polymer-Matrix Carbon Fiber Smart Layer to Normal Strain and Shear Strain

2011 ◽  
Vol 211-212 ◽  
pp. 421-424 ◽  
Author(s):  
Si Rong Zhu ◽  
Jing Li ◽  
Zhuo Qiu Li ◽  
Hua Sheng Zheng
Keyword(s):  
Carbon Fiber ◽  
Shear Strain ◽  
Polymer Matrix ◽  
Tensile Strain ◽  
Compressive Strain ◽  
Bending Test ◽  
Gauge Factor ◽  
Normal Strain ◽  
Frp Bar ◽  
New Type

The paper makes a comprehensive study on the sensitivity of a new type strain sensor named polymer-matrix carbon fiber smart layer. The sensitivity to tensile strain was gained by a uniaxial tension test. By a three-point bending test on a FRP bar stuck by the smart layer, the sensitivity to compressive strain was revealed and a lower gauge factor was obtained compared to the sensitivity to tensile strain. In addition, a pure shearing test was designed, revealing the sensitivity to shear strain.

Whole Field Structural Health Monitoring by Polymer-Matrix Carbon Fiber Smart Layer

2010 ◽  
Vol 148-149 ◽  
pp. 812-817 ◽  
Author(s):  
Hua Sheng Zheng ◽  
Si Rong Zhu ◽  
Zhuo Qiu Li ◽  
Lian Ye
Keyword(s):  
Carbon Fiber ◽  
Polymer Matrix ◽  
Health Monitoring ◽  
Effective Strain ◽  
Strain Sensor ◽  
Resistance Response ◽  
Resistance Change ◽  
Fiber Mats ◽  
Structure Damage ◽  
Three Point Bending

With epoxy reinforced by short carbon fiber mats, a skin-like strain sensor, polymer-matrix smart layer was developed, which can continuously cover the structural surface to sense strain for the whole filed. The smart layer was proved to be an effective strain sensor for tensile strain up to 0.8% by a monotonic tension experiment, exceeding this limit cause nonlinearity in the resistance response. The damage sensitivity of the smart layer was revealed by the monitoring for a FRP beam with prefabricated defect. Based on its sensitivities, the smart layers was applied in the health monitoring for a concrete beam under three-point bending, the result showed a good correlation between the resistance change of the smart layer and the load applied on the structure. The emergency of structure damage can be monitored by the turning point on the resistance-deflection curve of the smart layer.

scholarly journals Two-Dimensional Piezoresistive Response and Measurement of Sensitivity Factor of Polymer-Matrix Carbon Fiber Mat

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3072
Author(s):  
Min Wu ◽  
Li Huang ◽  
Xiaoyu Zhang ◽  
Jianzhong Chen ◽  
Yong Lv
Keyword(s):  
Carbon Fiber ◽  
Polymer Matrix ◽  
Longitudinal Direction ◽  
Experimental Results ◽  
Sensitivity Factor ◽  
Poisson Effect ◽  
Lateral Direction ◽  
Resistance Change ◽  
Change Rate ◽  
Tension Loading

Based on the piezoresistive effect, the piezoresistive constitutive relation of a carbon fiber mat under orthogonal strain was deduced. Considering the Poisson effect, the piezoresistive responses and measurement of the sensitivity factor of a polymer-matrix carbon fiber mat under bidirectional strain were studied by a two-times uniaxial tension loading method in different directions, which was pasted in the center area of a cruciform aluminum substrate. The relations between the resistance change rate and the orthogonal strains were established, the reasonability of which was confirmed by comparison with the experimental results. The results show that the longitudinal piezoresistive sensitivity factor C11 is 21.55, and the lateral piezoresistive sensitivity factor C12 is 24.15. Using these factors, the resistance change rate of another polymer-matrix carbon mat was predicted, which was made by the same technique, and the error between the predicted and the experimental results was 1.3% in the longitudinal direction and 6.1% in the lateral direction.

The Sensing Characteristics Responded by Resistance of Carbon Fiber Layer with Epoxy-Matrix

2011 ◽  
Vol 228-229 ◽  
pp. 1039-1042
Author(s):  
Xi Fang ◽  
Zhuo Qiu Li ◽  
Si Rong Zhu ◽  
Yong Lv
Keyword(s):  
Composite Material ◽  
Carbon Fiber ◽  
Uniaxial Tension ◽  
Temperature Sensor ◽  
Epoxy Matrix ◽  
Force Sensor ◽  
Resistance Testing ◽  
Fiber Layer ◽  
Temperature Resistance ◽  
Sensing Characteristics

Carbon fiber composed with epoxy-matrix is revealed to be a kind of functional composite material, which has sound sensing characteristics. The sensing ability of mechanic-electric character and temperature-electric character of carbon fiber layer based on the epoxy matrix was experimentally discussed in this paper. Through the uniaxial tension the CF layer reveals a good performance by resistance changing with response to the loading. In temperature-resistance testing, CF layer also has a good response to the temperature changing by its resistance varying. Carbon fiber composed with polymer will provides a new kind of sensor which can be used as force sensor and temperature sensor as well.

scholarly journals Flexural bearing capacity and failure mechanism of CFRP-aluminum laminate beam with double-channel cross-section

2021 ◽  
Vol 28 (1) ◽  
pp. 139-152
Author(s):  
Teng Huang ◽  
Dongdong Zhang ◽  
Yaxin Huang ◽  
Chengfei Fan ◽  
Yuan Lin ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Bearing Capacity ◽  
Failure Mechanism ◽  
Cross Section ◽  
Failure Criterion ◽  
Failure Modes ◽  
Channel Cross Section ◽  
Fiber Layer ◽  
Flexural Bearing Capacity ◽  
Double Channel

Abstract In this study, the flexural bearing capacity and failure mechanism of carbon fiber-reinforced aluminum laminate (CARALL) beams with a double-channel cross-section and a 3/2 laminated configuration were experimentally and numerically studied. Two types of specimens using different carbon fiber layup configurations ([0°/90°/0°]3 and [45°/0°/−45°]3) were fabricated using the pressure molding thermal curing forming process. The double-channel CARALL beams were subjected to static three-point bending tests to determine their failure behaviors in terms of ultimate bearing capacity and failure modes. Owing to the shortcomings of the two-dimensional Hashin failure criterion, the user-defined FORTRAN subroutine VUMAT suitable for the ABAQUS/Explicit solver and an analysis algorithm were established to obtain a progressive damage prediction of the CFRP layer using the three-dimensional Hashin failure criterion. Various failure behaviors and mechanisms of the CARALL beams were numerically analyzed. The results indicated that the numerical simulation was consistent with the experimental results for the ultimate bearing capacity and final failure modes, and the failure process of the double-channel CARALL beams could be revealed. The ultimate failure modes of both types of double-channel CARALL beams were local buckling deformation at the intersection of the upper flange and web near the concentrated loading position, which was mainly caused by the delamination failure among different unidirectional plates, tension and compression failure of the matrix, and shear failure of the fiber layers. The ability of each fiber layer to resist damage decreased in the order of 90° fiber layer > 0° fiber layer > 45° fiber layer. Thus, it is suggested that 90°, 0°, and 45° fiber layers should be stacked for double-channel CARALL beams.

scholarly journals Effect of Mechanical Pretreatments on Damage Mechanisms and Fracture Toughness in CFRP/Epoxy Joints

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1512
Author(s):  
Chiara Morano ◽  
Ran Tao ◽  
Marco Alfano ◽  
Gilles Lubineau
Keyword(s):  
Fracture Toughness ◽  
Carbon Fiber ◽  
Carbon Fibers ◽  
Polymer Matrix ◽  
Mechanical Tests ◽  
Adhesive Joints ◽  
Fiber Reinforced Polymers ◽  
Composite Joints ◽  
Damage Mechanisms ◽  
Grit Blasting

Adhesive bonding of carbon-fiber-reinforced polymers (CFRPs) is a key enabling technology for the assembly of lightweight structures. Surface pretreatment is necessary to remove contaminants related to material manufacturing and ensure bond reliability. The present experimental study focuses on the effect of mechanical abrasion on the damage mechanisms and fracture toughness of CFRP/epoxy joints. The analyzed CFRP plates were provided with a thin layer of surface epoxy matrix and featured enhanced sensitivity to surface preparation. Various degrees of morphological modification and fairly controllable carbon fiber exposure were obtained using sanding with emery paper and grit-blasting with glass particles. In the sanding process, different grit sizes of SiC paper were used, while the grit blasting treatment was carried by varying the sample-to-gun distance and the number of passes. Detailed surveys of surface topography and wettability were carried out using various methods, including scanning electron microscopy (SEM), contact profilometry, and wettability measurements. Mechanical tests were performed using double cantilever beam (DCB) adhesive joints. Two surface conditions were selected for the experiments: sanded interfaces mostly made of a polymer matrix and grit-blasted interfaces featuring a significant degree of exposed carbon fibers. Despite the different topographies, the selected surfaces displayed similar wettability. Besides, the adhesive joints with sanded interfaces had a smooth fracture response (steady-state crack growth). In contrast, the exposed fibers at grit-blasted interfaces enabled large-scale bridging and a significant R-curve behavior. While it is often predicated that quality composite joints require surfaces with a high percentage of the polymer matrix, our mechanical tests show that the exposure of carbon fibers can facilitate a remarkable toughening effect. These results open up for additional interesting prospects for future works concerning toughening of composite joints in automotive and aerospace applications.

Determination of transverse flexural and shear moduli of chopped carbon fiber tape-reinforced thermoplastic by vibration

2017 ◽  
Vol 52 (3) ◽  
pp. 395-404
Author(s):  
Xiuqi Lyu ◽  
Jun Takahashi ◽  
Yi Wan ◽  
Isamu Ohsawa
Keyword(s):  
Carbon Fiber ◽  
Beam Theory ◽  
Transversely Isotropic ◽  
High Volume ◽  
Bending Test ◽  
Thermoplastic Material ◽  
Shear Moduli ◽  
High Volume Production ◽  
Volume Production

Chopped carbon fiber tape-reinforced thermoplastic material is specifically developed for the high-volume production of lightweight automobiles. With excellent design processability and flexibility, the carbon fiber tape-reinforced thermoplastic material is manufactured by compressing large amounts of randomly oriented, pre-impregnated unidirectional tapes in a plane. Therefore, the carbon fiber tape-reinforced thermoplastic material presents transversely isotropic properties. Transverse shear effect along the thickness direction of carbon fiber tape-reinforced thermoplastic beam has a distinct influence on its flexural deformation. Accordingly, the Timoshenko beam theory combined with vibration frequencies was proposed to determine the set of transverse flexural and shear moduli. Meanwhile, the transverse flexural and shear moduli of carbon fiber tape-reinforced thermoplastic beam were finally determined by fitting all the first seven measured and calculated eigenfrequencies with the least squares criterion. In addition, the suggested thickness to length ratio for the 3-point bending test and Euler–Bernoulli model was given.

The Effect of Guide Sleeves on Shear Behavior of 3D Weaving Composites

2014 ◽  
Vol 597 ◽  
pp. 89-94 ◽  
Author(s):  
Xiao Chuan Wu ◽  
Zhong De Shan ◽  
Feng Liu ◽  
Yuan Wang
Keyword(s):  
Volume Fraction ◽  
Shear Behavior ◽  
Bending Test ◽  
Fracture Mechanisms ◽  
Study Guide ◽  
Fiber Layer ◽  
Resin Infusion ◽  
Interlaminar Shear ◽  
Shear Behaviors ◽  
3D Weaving

In this study, guide sleeves are brought into 3D weaving composite preforms. The process vacuum assisted resin infusion (VARI) was used to fabricate the 3D weaving composite with guide sleeves. The load-deflection curves and shear behaviors of the 3D weaving composites with guide sleeves were obtained by means of the 3-point bending test. The fracture micrographs of the materials were studied by SEM. The effects of guide sleeves’ diameter and interval on the shear behavior and fracture mechanisms of the 3D weaving composites were analyzed. The results showed that the guide sleeves could prevent delamination effectively by bridging fiber layer and pinning crack extending along the fiber layer. Fracture toughness of the composite parts increase because of deformation, fracture of guide sleeves and debonding of interface. The diameter and interval of guide sleeves is smaller, which means the volume fraction of guide sleeves is higher, the interlaminar shear strength higher for the bridging is stronger.

Study of the effect of the reinforcement direction on the identification of relaxation transitions of moisture-saturated carbon fiber VKU-25

2021 ◽  
Vol 87 (9) ◽  
pp. 38-43
Author(s):  
O. G. Ospennikova ◽  
P. S. Marakhovsky ◽  
N. N. Vorobyov ◽  
E. V. Nikolaev ◽  
A. I. Gulyaev ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Carbon Fiber ◽  
Polymer Matrix ◽  
Structural Parameters ◽  
Polymer Materials ◽  
Thermal Coefficient ◽  
Initial State ◽  
Relaxation Transitions

Thermodilatometric methods of analysis are used to study the structural parameters of polymer materials, however, when studying moisture-saturated compositions certain difficulties arise in their identification. The results of thermophysical tests of VKU-25 carbon fiber samples in the initial state and after moisture saturation are presented. It is shown that heat treatment of materials affects the recorded values of the glass transition temperature of the epoxy matrix. When the samples are exposed in water or above the water surface, the sorbate penetrates into the polymer at the same rate, which is confirmed by almost identical values of water absorption at the same exposure time. The estimates of the thermal coefficient of linear expansion (TCLE) of the samples in the range of 20 - 250°C are given. Moreover, it is shown that the glass transition temperature of the plasticized polymer matrix depends on the direction of fiber reinforcement. In the case of moisture-saturated carbon fiber (CF)heated to 210°C, the formation of main cracks occurs mainly at the fiber-matrix interface. The glass transition temperature (GTT) of the material in the dry state (176 - 177°C), appeared almost independent on the heating rate, whereas for water-saturated samples, GTT changes significantly and can be described by a polynomial of the 2nd order. After exposure of the carbon fiber under conditions of high temperature and humidity, two relaxation transitions corresponding to the systems occur in the polymer matrix: epoxidian oligomer— amine hardener and polyfunctional resin— amine hardener. The glass transition temperature is 132 and 159°C in the first and in the second, respectively. The results obtained can be used in the development of new polymer composite materials.

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