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.

scholarly journals Temperature dependence of statistical fatigue strengths for unidirectional carbon fiber reinforced plastics under tension loading

2019 ◽  
Vol 54 (14) ◽  
pp. 1797-1806 ◽  
Author(s):  
Masayuki Nakada ◽  
Yasushi Miyano
Keyword(s):  
Fatigue Strength ◽  
Carbon Fiber ◽  
Longitudinal Direction ◽  
Fiber Reinforced ◽  
Carbon Fiber Reinforced Plastics ◽  
Reinforced Plastics ◽  
The Matrix ◽  
Fiber Reinforced Plastics ◽  
Carbon Fiber Reinforced ◽  
Tension Loading

The formulation for time- and temperature-dependent statistical static and fatigue strengths for carbon fiber reinforced plastics laminates is newly proposed based on the physically serious role of resin viscoelasticity as the matrix of carbon fiber reinforced plastics. In this study, this formulation is applied to the tensile strength along the longitudinal direction of unidirectional carbon fiber reinforced plastics constituting the most important data for the reliable design of carbon fiber reinforced plastics structures which are exposed to elevated temperatures for a significant period of their operative life. The statistical distribution of the static and fatigue strengths under tension loading along the longitudinal direction of unidirectional carbon fiber reinforced plastics were measured at various temperatures by using resin-impregnated carbon fiber reinforced plastics strands as specimens. The master curves for the fatigue strength as well as the static strength of carbon fiber reinforced plastics strand were constructed based on the time–temperature superposition principle for the matrix resin viscoelasticity. The long-term fatigue strength of carbon fiber reinforced plastics strand can be predicted by using the master curve of fatigue strength.

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.

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.

scholarly journals Strain and damage self-sensing properties of carbon nanofibers/carbon fiber–reinforced polymer laminates

2017 ◽  
Vol 9 (2) ◽  
pp. 168781401668864 ◽  
Author(s):  
Yanlei Wang ◽  
Ruijuan Chang ◽  
Guipeng Chen
Keyword(s):  
Carbon Fiber ◽  
Carbon Nanofibers ◽  
Fiber Reinforced Polymer ◽  
Carbon Fiber Reinforced Polymer ◽  
Fiber Reinforced ◽  
Resistance Change ◽  
Reinforced Polymer ◽  
Carbon Fiber Reinforced ◽  
Tension Loading ◽  
Polymer Laminates

Unidirectional fiber-reinforced composites of “plain” carbon fiber–reinforced polymer laminates and carbon nanofibers modified carbon fiber–reinforced polymer laminates were prepared based on the manufacture of the epoxy resin modified with various contents of carbon nanofibers. The carbon nanofibers–modified epoxy matrix and carbon fiber–reinforced polymer laminates specimens were subject to constant amplitude cyclic tensile loading, quasi-static tension loading, and incremental cyclic tension loading while the values of their electrical resistance were monitored through electrical resistance technique. Resistance-change curves of carbon nanofibers/carbon fiber–reinforced polymer laminates indicated the changes in conductive percolation networks formed by carbon fibers or carbon nanofibers. These changes can identify the complex damage modes and the loss of mechanical integrity in laminates. The changes in resistance of specimens showed a nearly linear correlation with the strain, so the damage process of the carbon fiber–reinforced polymer laminates can be self-sensed according to the resistance-change curves. In addition, uniformly dispersed carbon nanofibers formed a network that spans the whole insulation area, which improved their self-sensing property of strain sensitivity without compromising the mechanical properties of the carbon fiber–reinforced polymer laminates. This technology can achieve the quantitative strain and damage self-sensing properties of nano-reinforced composites without any additional sensor, and it is bound to be a promising method for in situ health monitoring.

scholarly journals Prediction of Effective Thermal Conductivities of Four-Directional Carbon/Carbon Composites by Unit Cells with Different Sizes

2021 ◽  
Vol 11 (3) ◽  
pp. 1171
Author(s):  
Chang Xu ◽  
Zhihong Sun ◽  
Guowei Shao
Keyword(s):  
Carbon Fiber ◽  
Longitudinal Direction ◽  
Unit Cell ◽  
Carbon Composites ◽  
Temperature Boundary ◽  
The Matrix ◽  
Unit Cells ◽  
Experimental Values ◽  
Different Diameters ◽  
Thermal Conductivities

Two-unit cells developed to predict the effective thermal conductivities of four-directional carbon/carbon composites with the finite element method are proposed in this paper. The smaller-size unit cell is formulated from the larger-size unit cell by two 180° rotational transformations. The temperature boundary conditions corresponding to the two-unit cells are derived, and the validity is verified by the temperature and heat flux distributions at specific positions of the larger-size unit cell and the smaller-size unit cell. The thermal conductivities of the carbon fiber bundles and carbon fiber rods are measured firstly. Then, combined with the properties of the matrix, the effective thermal conductivities of the four-directional carbon/carbon composites are numerically predicted. The results in transverse direction predicted by the larger-size unit cell and the smaller-size unit cell are both higher than experimental values, which are 5.8 to 6.2% and 7.3 to 8.2%, respectively. In longitudinal direction, the calculated thermal conductivities of the larger-size unit cell and the smaller-size unit cell are 6.8% and 6.2% higher than the experimental results, respectively. In addition, carbon fiber rods with different diameters are set to clarify the influence on the effective thermal conductivities of the four-directional carbon/carbon composites.

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.

Enhancing the Thermoelectric Properties in Carbon Fiber/Cement Composites by Using Steel Slag

2013 ◽  
Vol 539 ◽  
pp. 103-107 ◽  
Author(s):  
Jun Qing Zuo ◽  
Wu Yao ◽  
Jun Jie Qin
Keyword(s):  
Carbon Fiber ◽  
Linear Relationship ◽  
Thermoelectric Power ◽  
Thermoelectric Properties ◽  
Steel Slag ◽  
Experimental Results ◽  
Cement Composites ◽  
Temperature Differential ◽  
High Concentration ◽  
Good Linear

Thermoelectric properties of steel slag-carbon fiber/cement composites were studied in this paper. The effect of steel slag content on thermoelectric properties was focused on especially. The experimental results show that the addition of steel slag leads to an increase in the positive thermoelectric power of the cabon fiber/cement composites. The highest absolute thermoelectric power of carbon fiber/cement composites was rendered as positive as 14.4µV/°C by using steel slag, which had a high concentration of holes. Beside, a good linear relationship was observed between thermoelectric power and temperature differential on the specimen.

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.

Detecting and Rectifying Vehicle Malicious Misbehavior for Intersection Movement Assist: A Sensor-Based Misbehavior Detection Study

2021 ◽  
pp. 036119812110513
Author(s):  
Boon Teck Ong ◽  
Joshua Kolleda ◽  
Saleh Mousa ◽  
Scott Andrews ◽  
Dennis Fleming ◽  
...  
Keyword(s):  
False Positive ◽  
Research Effort ◽  
False Negative ◽  
Field Tests ◽  
Longitudinal Direction ◽  
Third Party ◽  
Lateral Direction ◽  
Misbehavior Detection ◽  
Safety Application ◽  
Hazard Scenario

Recent developments in wireless communication technologies have led to the evolution of connectivity between vehicles. Maintaining connectivity between vehicles increases a vehicle’s awareness of other nearby vehicles, which can be used in safety applications. Identification of malicious misbehaving vehicles plays an important role in road safety. This research establishes the minimum detectable error (MDE) boundary for relative position between the observer and status vehicles (SV) using vehicle sensor and GPS error profile from field tests and established minimum standards. The results demonstrated that the MDE increases in the lateral direction (side-to-side) with the increase in relative distance between the observer and status vehicles (OV and SV) while remaining the same in the longitudinal direction (front-to-back). This research effort explores the use of Sensor-Based Misbehavior Detection (SBMD) with current specifications and the defined MDE boundary for implementation in the Intersection Movement Assist (IMA) safety application to rectify false positive and false negative hazard messages propagated by a malicious misbehaving vehicle. The simulation approach used in this research quantifies the total number of false positive/negative hazard detections received by a third-party vehicle (TPV) using the IMA safety application and assesses the capability of the OV equipped with SBMD to rectify the false positive/negative hazard detection. In cases where there was no hazard, SBMD produced an 83% to 90% improvement in the reduction of false positive hazard detections. In the cases with hazard scenario, where the SV is in the not-safe-to-cross zone, SBMD produced an 80% to 99% improvement in application performance.

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