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.

Buckling and Tensile Strain Capacity of Girth Welded 48″ X80 Pipeline

2013 ◽  
Author(s):  
Satoshi Igi ◽  
Mitsuru Ohata ◽  
Takahiro Sakimoto ◽  
Junji Shimamura ◽  
Kenji Oi
Keyword(s):  
Crack Growth ◽  
Tensile Strain ◽  
Compressive Strain ◽  
Bending Test ◽  
Ductile Crack ◽  
Pipe Surface ◽  
Strain Capacity ◽  
Ductile Crack Growth ◽  
Strain Limit ◽  
Tensile Strain Capacity

This paper presents the experimental and analytical results focused on the compressive and tensile strain capacity of X80 linepipe. A full-scale bending test of girth welded 48″ OD X80 linepipes was conducted to investigate the compressive strain limit regarding to the local buckling and tensile strain limit regarding to the girth weld fracture. As for the compressive buckling behavior, one large developing wrinkle and some small wrinkles on the pipe surface were captured relatively well from observation and strain distribution measurement after pipe reaches its endurable maximum bending moment. The tensile strain limit is discussed from the viewpoint of competition of two fracture phenomena: ductile crack initiation / propagation from an artificial notch at the HAZ of the girth weld, and strain concentration and necking / rupture in the base material. The ductile crack growth behavior from the girth weld notch is simulated by FE-analysis based on the proposed damage model, and compared with the experimental results. In this report, it is also demonstrated that the simulation model can be applicable to predicting ductile crack growth behaviors from a circumferentially notched girth welded pipe with internal high pressure subjected to post-buckling loading.

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 Experimental Investigation of Crack Propagation and Strain Fields Evolution around a Crack Tip in 5A05 Aluminum Alloy

Metals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 685
Author(s):  
Jijun Li ◽  
Wencai Li ◽  
Chunwang Zhao ◽  
Yongming Xing ◽  
Fengchao Lang ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Shear Strain ◽  
Crack Tip ◽  
Bending Test ◽  
Propagation Path ◽  
Normal Strain ◽  
Load Direction ◽  
Strain Fields

In situ scanning electron microscopy three-point bending test was employed in this study to investigate the crack initiation and propagation in 5A05 aluminum alloy. The microscale strain fields around the crack tip were measured by using the geometric phase analysis method. Results show that prior to the crack initiation, the normal strain εyy (y direction is perpendicular to the load direction) was tensile around the notch, whereas the normal strain εxx (x direction is parallel to the load direction) was compressive around the notch. The shear strain εxy was nearly zero. With the increase in load, the normal strains εyy and εxx gradually increased, but the change in shear strain εxy was not evident. When the stresses at several sharp points at the notch root reached the breaking strengths, a few microcracks initiated at these points. At this moment, the normal strains εyy and εxx were much greater than the shear εxy, and dominated the strain fields around the crack tip. In the crack propagation process, the normal strains εyy and εxx, and the shear strain εxy dominated the strain fields around the crack tip, thereby leading to a Z-form of crack propagation path in the specimen.

Shear-strain-mediated photoluminescence manipulation in two-dimensional transition metal dichalcogenides

2D Materials ◽  
2021 ◽  
Author(s):  
Hyeong-Yong Hwang ◽  
Sehyuk Lee ◽  
Yong-Hoon Kim ◽  
Farman Ullah ◽  
Chinh Tam Le ◽  
...  
Keyword(s):  
Transition Metal ◽  
Shear Strain ◽  
Compressive Strain ◽  
Transition Metal Dichalcogenides ◽  
Normal Strain ◽  
Two Dimensional ◽  
Band Structures ◽  
Electronic Band ◽  
Selection Rules ◽  
Metal Dichalcogenides

Abstract In two-dimensional transition metal dichalcogenides, normal strain can modulate electronic band structures, yet leaving the optical selection rules intact. In contrast, a shear strain can perturb the spin-valley locked band structures and possibly induce mixing of the spin subbands which in turn can transfer oscillator strength between spin-allowed bright and spin-forbidden dark excitons. Here, we report a novel scheme to manipulate photoluminescence in a monolayer WSe2-MoSe2 lateral heterostructures, controlled by an external bending method in which strong out-of plane shear strain (OSS) of up to 5.6% accompanies weak in-plane normal strain up to 0.72%. The spectra revealed a striking dependence on the bending direction that is stagnant in the negative (compressive) strain region and then rapidly changes with increasing positive (tensile) strain. The dependency of the photoluminescence signal under tensile bending was represented not only by the large energy shift (>40 meV) of the lowest excited states of both the WSe2 and MoSe2 monolayers, but also by the tendency to violate the optical selection rules that brightens (darkens) the excitons of the WSe2 (MoSe2) side. The analyses on the observed energy shifts and PL intensity changes confirm the different origins in compressive bending compared with tensile bending. The well-established band-anticrossing is identified to be affecting only the compressive deformation region. The spectral changes in the tensile region, on the other hand, originates mainly from the generation of an off-diagonal perturbation to a spin-specific Hamiltonian induced by OSS. The degree of spin-state mixing, which correlates precisely with the spin-flip coefficient of the theoretical model, is further represented by the OSS matrix elements, the spin splitting energy, and the shear deformation potential.

Sensitivity of the Carbon Fiber Interface in Epoxy

2011 ◽  
Vol 69 ◽  
pp. 79-82
Author(s):  
Hua Sheng Zheng ◽  
Si Rong Zhu ◽  
Zhuo Qiu Li ◽  
Jing Li
Keyword(s):  
Carbon Fiber ◽  
Polymer Matrix ◽  
Fiber Composite ◽  
Local Area ◽  
Interfacial Stress ◽  
Gauge Factor ◽  
Carbon Fiber Composites ◽  
Strain Sensing ◽  
Carbon Fiber Composite ◽  
Cfrp Laminates

In order to improve the gauge factor of polymer-matrix carbon fiber reinforced composites (CFRP) for strain sensing, the carbon fiber sensitive interface was constructed in epoxy by effectively overlapping the CFRP laminates in local area. The strain sensitivities of the carbon fiber interface were proved by the cyclic tension test on the base specimens covered by the carbon fiber composites with the sensitive interface, and their much bigger gauge factors were revealed by the comparison with the polymer-matrix continuous carbon fiber composite. The sensitivity of the carbon fiber interface is originated from the change of the interfacial points due to the interfacial stress.

scholarly journals Development of Highly Sensitive Strain Sensor Using Area-Arrayed Graphene Nanoribbons

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1701
Author(s):  
Ken Suzuki ◽  
Ryohei Nakagawa ◽  
Qinqiang Zhang ◽  
Hideo Miura
Keyword(s):  
Graphene Nanoribbons ◽  
Strain Sensor ◽  
Strain Sensors ◽  
Sensitive Strain ◽  
Bending Test ◽  
Gauge Factor ◽  
Four Point Bending ◽  
Current Voltage ◽  
Highly Sensitive ◽  
Current Voltage Relationship

In this study, a basic design of area-arrayed graphene nanoribbon (GNR) strain sensors was proposed to realize the next generation of strain sensors. To fabricate the area-arrayed GNRs, a top-down approach was employed, in which GNRs were cut out from a large graphene sheet using an electron beam lithography technique. GNRs with widths of 400 nm, 300 nm, 200 nm, and 50 nm were fabricated, and their current-voltage characteristics were evaluated. The current values of GNRs with widths of 200 nm and above increased linearly with increasing applied voltage, indicating that these GNRs were metallic conductors and a good ohmic junction was formed between graphene and the electrode. There were two types of GNRs with a width of 50 nm, one with a linear current–voltage relationship and the other with a nonlinear one. We evaluated the strain sensitivity of the 50 nm GNR exhibiting metallic conduction by applying a four-point bending test, and found that the gauge factor of this GNR was about 50. Thus, GNRs with a width of about 50 nm can be used to realize a highly sensitive strain sensor.

scholarly journals The research on precise forming technology of “λ” type composite skin

2021 ◽  
Vol 30 ◽  
pp. 263498332199474
Author(s):  
Qiang Guo ◽  
Kai He ◽  
Hengyuan Xu ◽  
Youyi Wen
Keyword(s):  
Carbon Fiber ◽  
Middle Layer ◽  
Fiber Reinforced ◽  
Process Verification ◽  
Forming Technology ◽  
Fiber Reinforced Materials ◽  
New Type ◽  
Carbon Fiber Reinforced ◽  
Type Composite ◽  
Reinforced Materials

With the application of “ λ” type composite skin becoming more and more extensive and diversified, its precise forming technology is also widely concerned. This article mainly solves the quality problems of “ λ” type corner area, such as delamination dispersion and surface wrinkle, which exist in reality commonly in the manufacturing process. The prepreg is heated along the corner area of the tooling to solve the problem that prepreg is difficult to be compacted due to the large modulus of carbon fiber in “ λ” type corner area. Furthermore, two precompaction tests are creatively increased at 16 layers (middle layer) and 32 layers (last layer) for the thick structure, respectively, to ensure the compaction effect of the blank. In addition, combined with the characteristics of highly elastic rubber and carbon fiber-reinforced materials, a new type of soft mold structure with proper flexibility and good stiffness is proposed innovatively through the reasonable placement of carbon fiber-reinforced materials and the setting of exhaust holes according to the structure characteristics of “ λ” type root skin. Through further process verification, it is shown that the improved process has effectively solved the problems of wrinkles and internal delamination at the sharp corners of parts and realized zero-defect manufacturing of “ λ” type root skin for the first time.

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.

Reliability-Based Balanced Condition for Strengthened RC Beams

2013 ◽  
Vol 756-759 ◽  
pp. 25-28 ◽  
Author(s):  
Chun Xia Li ◽  
Zhi Sheng Ding ◽  
Shi Lin Yan ◽  
Jun Ming Chen
Keyword(s):  
Reinforced Concrete ◽  
Carbon Fiber ◽  
Stress Distribution ◽  
Tensile Strain ◽  
Concrete Beams ◽  
Reinforced Concrete Beams ◽  
Experimental Result ◽  
Rc Beams ◽  
Yield Strain ◽  
Reliability Indicator

Based on the experimental result of the flexure capability of reinforced concrete beams strengthened by carbon fiber sheets, the stress distribution changes only after steel yielding and carbon fiber sheets function better. However serious the extent of the damage is before strengthened, the tensile strain of main steel reaches about 1.6 times of the yield strain for the secondary grade of steel as failure happens. To satisfy the object reliability indicator, reliability is analyzed using the ratio of the steel strain at the balanced failure to the yield strain as variable to obtain its optimum value, which is coincide with the experimental result, and makes better consistency between calculated reliability indicator and object reliability indicator.

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