scholarly journals Analysis of Nonlinear Shear Deformations in CFRP and GFRP Textile Laminates

2011 ◽  
Vol 70 ◽  
pp. 363-368 ◽  
Author(s):  
Himayat Ullah ◽  
Andy R. Harland ◽  
Robert Blenkinsopp ◽  
Tim Lucas ◽  
Dan Price ◽  
...  
Keyword(s):  
Deformation Behaviour ◽  
Production Costs ◽  
Image Correlation ◽  
Woven Composites ◽  
Correlation Technique ◽  
Shear Deformations ◽  
Full Field ◽  
Damage Initiation ◽  
Reinforced Polymer ◽  
Fibre Reinforced Polymer

Carbon fibre-reinforced polymer (CFRP) and glass fibre-reinforced polymer (GFRP) woven composites are widely used in aerospace, automotive and construction components and structures thanks to their lower production costs, higher delamination and impact strengths. They can also be used in various products in sports industry. These products are exposed to different in-service conditions such as large tensile and bending deformations. Composite materials, especially ±45° symmetric laminates subjected to tensile loads, exhibit significant material as well as geometric non-linearity before damage initiation, particularly with respect to shear deformations. Such a nonlinear response needs adequate means of analysis and investigation, the major tools being experimental tests and numerical simulations. This research deals with modelling the nonlinear deformation behaviour of CFRP and GFRP woven laminates subjected to in-plane tensile loads. The mechanical behaviour of woven laminates is modelled using nonlinear elasto-plastic as well as material models for fabrics in commercial finite-element code Abaqus. A series of tensile tests is carried out to obtain an in-plane full-field strain response of [+45/-45]2s CFRP and GFRP laminates using digital image correlation technique according to ASTM D3518/D3518M-94. The obtained results of simulations are in good agreement with experimental data.

Using digital image correlation to evaluate the bond between carbon fibre-reinforced polymers and timber

2021 ◽  
pp. 147592172110060
Author(s):  
Hugo C Biscaia ◽  
João Canejo ◽  
Shishun Zhang ◽  
Raquel Almeida
Keyword(s):  
Digital Image Correlation ◽  
Carbon Fibre ◽  
Digital Image ◽  
Image Correlation ◽  
Strain Gauges ◽  
Correlation Technique ◽  
Digital Image Correlation Technique ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

The use of optic measurements such as digital image correlation to take strain measurements of fibre-reinforced polymers bonded to a substrate has been on the increase recently. This technique has proven to be useful to fully characterize the bond behaviour between two materials. Although modern digital cameras can take high-definition photos, this task is far from simple due to the tiny displacements that need to be measured. Consequently, digital image correlation measurements lead to relative errors that, at an initial stage of the debonding process, are higher than those calculated close to the debonding of the fibre-reinforced polymer from the substrate. This study aims to evaluate and analyse the use of the digital image correlation technique on the bond between carbon fibre-reinforced polymer laminates and timber when subjected to a pull-out load consistent with fracture Mode II. To allow the quantification of the relative errors obtained from the digital image correlation measurements during the full debonding process, several strain gauges were used to measure the strains in the carbon fibre-reinforced polymer composite. The accuracy of the digital image correlation measurements is analysed by comparing it with those obtained from the strain gauges, which is a very well-established measuring technique. Another contribution of this study is to check the versatility of the digital image correlation measurements on a broader range of situations. To that end, several timber prisms were bonded with seven different bonding techniques with and without the installation of a mechanical anchorage at the carbon fibre-reinforced polymer unpulled end. The results showed that the digital image correlation technique was able to track the slips calculated from the strain gauge measurements until the debonding load, but after that, some difficulties to measure the displacements of the anchored carbon fibre-reinforced polymer-to-timber joints were detected. The digital image correlation technique also over predicted bond stresses when compared with those taken from the strain gauges, which led to bond–slip relationships with higher bond stresses.

Successive Translucent and Opaque Shear Bands Accompanied by a Pronounced Periodic Waves Observed in a Polypropylene (PP) Processed by Single ECAE Pass

2011 ◽  
Vol 423 ◽  
pp. 12-25
Author(s):  
R. Boulahia ◽  
Taoufik Boukharouba ◽  
Fahmi Zaïri ◽  
M. Naït-Abdelaziz ◽  
J.M. Gloaguen ◽  
...  
Keyword(s):  
Equal Channel Angular Extrusion ◽  
Deformation Behaviour ◽  
Shear Bands ◽  
Back Pressure ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Correlation Technique ◽  
Shear Direction ◽  
Periodic Waves ◽  
Full Field

The equal channel angular extrusion (ECAE) is an ingenious severe plastic deformation process used to modify texture and microstructure without reducing sample cross-section. The ECAE of polypropylene (PP) was conducted under various extrusion velocities and back-pressure levels using a 90° die. The application of single ECAE pass to PP was meticulously investigated at room temperature. The ECAE-induced deformation behaviour was examined in relation to the load versus ram displacement curves. Depending on extrusion conditions, PP displayed various types of plastic flow. For ram velocities beyond 4.5 mm/min, severe shear bands consisting of successive translucent and opaque bands were observed, accompanied on the top surface by more or less pronounced periodic waves. Although the application of a back-pressure significantly reduced the wave and shear-banding phenomena, slightly inhomogeneous shear deformation was still observed. Shear bands were only suppressed by decreasing extrusion velocity. The strain-induced crystalline microstructure was investigated by X-ray scattering. Shear-banded samples exhibited a strong texturing of the (hk0) planes along the shear direction in the translucent bands whereas perfect crystalline isotropy appeared in the opaque bands. Application of backpressure and/or reducing ram velocity resulted in uniform texturing along the extruded sample. Yet, texturing changed from single shear to twin-like shear orientation about the shear direction. Mechanical properties changes of the extruded specimens due to back-pressure and extrusion velocity effects were analyzed via uniaxial tensile tests. The tensile samples displayed multiple strain localizations in shear-banded materials whereas quite homogeneous deformation appeared for non-banded ones. These effects were connected with the crystalline texturing. The results also revealed significant increase in the strain hardening after ECAE. Full-field strain was measured under tensile loading using an optical strain measuring technique based upon Digital image correlation technique, suitable for large deformation, which confirms these effects.

scholarly journals Identification of the Mechanical Properties of Superconducting Windings Using the Virtual Fields Method

2010 ◽  
Vol 24-25 ◽  
pp. 379-384
Author(s):  
J.H. Kim ◽  
F. Nunio ◽  
Fabrice Pierron ◽  
P. Vedrine
Keyword(s):  
Least Square Method ◽  
Numerical Differentiation ◽  
Tensile Tests ◽  
Least Square ◽  
Image Correlation ◽  
Stereo Image ◽  
Correlation Technique ◽  
Virtual Fields Method ◽  
Displacement Fields ◽  
Full Field

Tensile tests were performed in order to identify the stiffness components of superconducting windings in the shape of rings (also called ‘double pancakes’). The stereo image correlation technique was used for full-field displacement measurements. The strain components were then obtained from the measured displacement fields by numerical differentiation. Because differentiation is very sensitive to spatial noise, the displacement maps were fitted by polynomials before differentiation using a linear least-square method. Then, in the orthotropy basis, the four in-plane stiffnesses of the double pancake were determined using the Virtual Fields Method.

scholarly journals Deformation and damage evolution of a full-scale adhesive joint between a steel bracket and a sandwich panel for naval application

2020 ◽  
pp. 095440622094712
Author(s):  
Pankaj R Jaiswal ◽  
R Iyer Kumar ◽  
M Saeedifar ◽  
MN Saleh ◽  
Geert Luyckx ◽  
...  
Keyword(s):  
Damage Evolution ◽  
Sandwich Panel ◽  
Deformation Behaviour ◽  
Local Strain ◽  
Tensile Tests ◽  
Full Scale ◽  
Image Correlation ◽  
Cohesive Failure ◽  
Local Strains ◽  
Damage Initiation

The increasing interest for the application of adhesive joints in naval superstructures motivates researchers to gain an in-depth understanding of the mechanical behaviour and failure mechanisms of these joints. This work reports on an experimental study of the deformation behaviour and damage evolution of a full-scale multi-material joint using different instrumentation techniques. Adhesively bonded joints of steel to sandwich panel components have been subjected to quasi-static tensile tests during which the global deformation of the joint and local strain distributions were monitored using digital image correlation (DIC). During one particular tensile test, fibre optic Bragg sensors (FBG) were also applied to the specimen’s surface at different locations in order to quantify the evolution of local strains. Additionally, acoustic emission (AE) sensors were installed in order to monitor damage initiation and evolution with increasing levels of imposed deformation. This test showcased adhesive failure at the interface of the steel adherend and the adhesive, while cohesive failure was observed within the adhesive and skin failure at the interface between adhesive and the composite skin of the sandwich panel. The post-mortem observed failures modes were compared to the acoustic events that originated during the test due to damage initiation and propagation within the joint. The evolution of the different sensor signals, i.e. the damage expressed as cumulative AE energy and local strains measured with Bragg sensors and DIC, are mutually compared and acceptable correlation is found.

scholarly journals Investigation on application of basalt materials as reinforcement for flexural elements of concrete bridges

2015 ◽  
Vol 10 (3) ◽  
pp. 201-206 ◽  
Author(s):  
Viktor Gribniak ◽  
Aleksandr K. Arnautov ◽  
Gintaris Kaklauskas ◽  
Vytautas Tamulenas ◽  
Edgaras Timinskas ◽  
...  
Keyword(s):  
Deformation Behaviour ◽  
High Strength ◽  
Concrete Bridges ◽  
Polymer Materials ◽  
Structural Stiffness ◽  
New Materials ◽  
Basalt Fibre ◽  
Reinforced Polymer ◽  
Polymer Sheets ◽  
Fibre Reinforced Polymer

Basalt polymers are rather new materials for civil engineering; therefore, identification of peculiarities and limitations of application of such polymers in concrete structures (particularly bridges) is of vital importance. This paper experimentally investigates deformation behaviour and cracking of flexural elements, which are predominant parameters governing serviceability of the bridges. Unlike a common practice, the present study is not limited by the analysis of concrete beams reinforced with the polymer bars; it also considers effectiveness of basalt fibre reinforced polymer sheets for repairing the beams. The analysis has revealed that a combination of the high strength and elasticity polymer materials governs the effective repair of the beams by significantly increasing (up to 40%) the structural stiffness.

scholarly journals Prestressing low clinker structural concrete elements by ultra-high modulus carbon fibre reinforced polymer tendons

2021 ◽  
Vol 54 (1) ◽  
Author(s):  
Tobias Dominik Lämmlein ◽  
Janis Justs ◽  
Giovanni Pietro Terrasi ◽  
Pietro Lura
Keyword(s):  
Carbon Fibre ◽  
High Performance ◽  
High Performance Concrete ◽  
Maximum Load ◽  
Image Correlation ◽  
High Modulus ◽  
Transfer Length ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

AbstractThe combination of low clinker high-performance concrete (LCHPC) and ultra-high modulus (UHM) carbon fibre reinforced polymer (CFRP) tendons was recently proposed for prestressed structural elements. The 70% reduction in cement content resulting in limited creep and shrinkage of the LCHPC in comparison to a conventional high-performance concrete (HPC) and the very high UHM-CFRP tendon stiffness (> 509 GPa) were expected to impact the mechanical behaviour of such structures. This study focuses on the behaviour of 3 m-long beam specimens during prestressing, concrete hardening and in 4 point-bending experiments. Fibre optic sensors were implemented inside the CFRP tendons to measure strain during those stages and a digital image correlation system was employed to monitor the 4-point-bending tests. After 28 days, the LCHPC recipe, despite a 70% cement reduction and much smaller environmental footprint, did not show measurable differences in the prestress loss behaviour in comparison to a conventional HPC. The UHM-CFRP prestressing tendons, because of their stiffness, showed both higher prestress losses of around 40% and on average a nearly doubled prestress transfer length. However, they increased the beam`s maximum load-bearing capacity by 21% and showed 47% less deflection at failure in comparison to beams prestressed with the standard modulus (UTS)-CFRP tendons.

Characterization of LIGA Microsystems Using Digital Image Correlation Technique and SEM Imaging

Aerospace ◽  
2005 ◽  
Author(s):  
Helena (Huiqing) Jin ◽  
Wei-Yang Lu ◽  
Jeff Chames ◽  
Nancy Yang
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Speckle Pattern ◽  
Image Correlation ◽  
Specimen Surface ◽  
Correlation Technique ◽  
Sem Images ◽  
Full Field ◽  
Speckle Patterns ◽  
Dic Technique

A new experimental technique was developed to characterize the mechanical properties of LIGA (an acronym from German words for lithography, electroplating, and molding) materials. An advanced imaging capability, scanning electron microscopy (SEM), with an integrated loading stage allows the acquisition of in situ microstructural images at the micro scale during loading. The load is measured directly from a load cell, and the displacement field is calculated from the SEM images based on the digital image correlation (DIC) technique. The DIC technique is a full-field deformation measurement technique which obtains displacement fields by comparing random speckle patterns on the specimen surface before and after deformation. The random speckle patterns are typically generated by applying a thin layer of material with high contrast to a specimen surface. Alternatively, DIC can also be applied using the microstructural features of a surface as texture patterns for correlation. DIC technique is ideally suited to characterize the deformation field of MEMS structures without the need to generate a random speckle pattern, which can be very challenging on the micro and nanoscale. In this paper, the technique is experimentally demonstrated on a LIGA specimen. The digital images showing LIGA surface features acquired during the loading can serve as random patterns for the DIC method. Therefore, full-field displacement and strain can be obtained directly on the specimen and the errors incurred by the testing system can be eliminated.

scholarly journals Strengthening of Hollow Square Sections under Compression Using FRP Composites

2014 ◽  
Vol 2014 ◽  
pp. 1-19 ◽  
Author(s):  
M. C. Sundarraja ◽  
P. Sriram ◽  
G. Ganesh Prabhu
Keyword(s):  
Failure Modes ◽  
Deformation Behaviour ◽  
Three Dimensional ◽  
Local Buckling ◽  
Experimental Results ◽  
Frp Composites ◽  
Reinforced Polymer ◽  
Load Carrying ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

The feasibility study on carbon fibre reinforced polymer (CFRP) fabrics in axial strengthening of hollow square sections (HSS) was investigated in this paper. CFRP was used as strips form with other parameters such as the number of layers and spacing of strips. Experimental results revealed that the external bonding of normal modulus CFRP strips significantly enhanced the load carrying capacity and stiffness of the hollow sections and also reduced the axial shortening of columns by providing external confinement against the elastic deformation. The increase in the CFRP strips thickness effectively delayed the local buckling of the above members and led to the inward buckling rather than outward one. Finally, three-dimensional nonlinear finite element modeling of CFRP strengthened hollow square sectionswas created by using ANSYS 12.0 to validate the results and the numerical results such as failure modes and load deformation behaviour fairly agreed with the experimental results.

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