Digital image correlation (DIC) for measurement of strains and displacements in coarse, low volume-fraction FRP composites used in civil infrastructure

Castillo, Enrique del Rey; Allen, Tom; Henry, Richard; Griffith, Michael; Ingham, Jason

doi:10.1016/j.compstruct.2019.01.024

Cited by 61 publications

(26 citation statements)

References 44 publications

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“…The corresponding step size was 5. The strain was calculated result from the average displacement of a couple of adjacent calculation subsets, so the strain at the edge could not be determined [29,[34][35][36][37][38]. The tensile tests with the same loading conditions were repeated three times.…”

Section: Full-field Strain Analysismentioning

confidence: 99%

The Effects of Strain Rates on Mechanical Properties and Failure Behavior of Long Glass Fiber Reinforced Thermoplastic Composites

Cui

Wang

et al. 2019

Polymers

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Long glass fiber reinforced thermoplastic composites have been increasingly used in automotive parts due to their excellent mechanical properties and recyclability. However, the effects of strain rates on the mechanical properties and failure mechanisms of long glass fiber reinforced polypropylene composites (LGFRPPs) have not been studied systematically. In this study, the effects of strain rates (from 0.001 s−1 to 400 s−1) on the mechanical properties and failure mechanism of LGFRPPs were investigated. The results showed that ultimate strength and fracture strain of the LGFRPPs increased obviously, whereas the stiffness remained essentially unchanged with the strain rates from low to high. The micro-failure modes mainly consisted of fibers pulled out, fiber breakage, interfacial debonding, matrix cracking, and ductile to brittle (ductile pulling of fibrils/micro-fibrils) fracture behavior of the matrix. As the strain rates increased, the interfacial bonding properties of LGFRPPs increased, resulting in a gradual increase of fiber breakage at the fracture surface of the specimen and the gradual decrease of pull-out. In this process, more failure energy was absorbed, thus, the ultimate strength and fracture strain of LGFRPPs were improved.

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Section: Full-field Strain Analysismentioning

confidence: 99%

The Effects of Strain Rates on Mechanical Properties and Failure Behavior of Long Glass Fiber Reinforced Thermoplastic Composites

Cui

Wang

et al. 2019

Polymers

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“…Digital image correlation (DIC), or Particle Image Velocimetry (PIV), has since its introduction in the 1980s evolved into one of the most versatile and widespread techniques in experimental mechanics [1][2][3][4][5][6]. Recent examples are found in diverse scientific fields such as biomechanics [7], infrastructure [8], material science [9], composite structures [10], and microfluidistics [11], but the technique is not restricted to these scientific fields. A quick search on a popular search engine lists over 50,000 contributions out of which 16,000 are published throughout the last four years.…”

Section: Introductionmentioning

confidence: 99%

Gradient Correlation Functions in Digital Image Correlation

Sjödahl

2019

Applied Sciences

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The performance of seven different correlation functions applied in Digital Image Correlation has been investigated using simulated and experimentally acquired laser speckle patterns. The correlation functions were constructed as combinations of the pure intensity correlation function, the gradient correlation function and the Hessian correlation function, respectively. It was found that the correlation function that was constructed as the product of all three pure correlation functions performed best for the small speckle sizes and large correlation values, respectively. The difference between the different functions disappeared as the speckle size increased and the correlation value dropped. On average, the random error of the combined correlation function was half that of the traditional intensity correlation function within the optimum region.

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“…An actual testing coupon for the optical deformation measurement is shown in Figure 3b. All the set parameters for analysis of images was followed by Reference [25], therefore, the re-projection error caused by DSLR cameras was around 0.05 pixels, the displacement and strain difference were around 6% and 0.06%, respectively. More details regarding the level of error in the DIC method when in combination with inexpensive DSLR cameras can be found in the literature [24,25].…”

Section: Characterizationmentioning

confidence: 99%

The Failure Mechanism of Composite Stiffener Components Reinforced with 3D Woven Fabrics

Memon

Qiu

et al. 2019

Materials

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Composite industry has long been seeking practical solutions to boost laminate through-thickness strengths and interlaminar shear strengths (ILSS), so that composite primary structures, such as stiffeners, can bear higher complex loadings and be more delamination resistant. Three dimensional (3D) woven fabrics were normally employed to render higher transverse and shear strengths, but the difficulty and high expense in producing such fabrics make it a hard choice. Based on a novel idea that the warp yarns that interlock layers of the weft yarns might provide adequate fiber crimps that would allow the interlaminar shear or radial stresses to be transferred and borne by the fibers, rather than by the relatively weaker matrix resin, thus improving the transverse strengths, this work provided a two point five dimensional (2.5D) approach as a practical solution, and demonstrated the superior transverse performances of an economical 2.5D shallow-bend woven fabric (2.5DSBW) epoxy composites, over the conventional two dimensional (2D) laminates and the costly 3D counterpart composites. This approach also produced a potential candidate to fabricate high performance stiffeners, as shown by the test results of L-beams which are common structural components of any stiffeners. This study also discovered that an alternative structure, namely a 2.5D shallow-straight woven fabric (2.5DSSW), did not show any advantages over the two control structures, which were a 2D plain weave (2DPW) and a 3D orthogonal woven fabric (3DOW) made out of the same carbon fibers. Composites of these structures in this study were conveniently fabricated using a vacuum-assisted resin infusion process (VARI). The L-beams were tested using a custom-made test fixture. The strain distribution and failure mode analysis of these beams were conducted using Digital Image Correlation (DIC) and X-ray Computed Tomography Scanning (CT). The results demonstrated that the structures containing Z-yarns or having high yarn crimps or waviness, such as in cases of 3DOW and 2.5DSBW, respectively, were shown to withstand high loadings and to resist delamination, favorable for the applications of high-performance structural composites.

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Digital image correlation (DIC) for measurement of strains and displacements in coarse, low volume-fraction FRP composites used in civil infrastructure

Cited by 61 publications

References 44 publications

The Effects of Strain Rates on Mechanical Properties and Failure Behavior of Long Glass Fiber Reinforced Thermoplastic Composites

The Effects of Strain Rates on Mechanical Properties and Failure Behavior of Long Glass Fiber Reinforced Thermoplastic Composites

Gradient Correlation Functions in Digital Image Correlation

The Failure Mechanism of Composite Stiffener Components Reinforced with 3D Woven Fabrics

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