“…These localised strains are possibly due to the localised plastic deformation of the matrix and micro-damage such as localised de-bonding or micro-cracking, which ultimately result in fibre breakage. This is in agreement with findings in the literature 3,26,55 where microstructural analysis of the composites shows plastic deformation of matrix. Because of the constraining effect of surrounding fibres, extra strain is induced in the matrix as seen by the localised strains in the DIC map.Figure 9.DIC generated normal strain in longitudinal direction (bold-italiceyy) maps showing inhomogeneity distribution for a tensile test specimen with (a) 0°/90° and (b) ±45° fibre orientation, images were registered at applied true tensile strain in y direction of 1.3% and 10%, respectively.…”
Section: Resultssupporting
confidence: 93%
“…These localised strains are possibly due to the localised plastic deformation of the matrix and micro-damage such as localised de-bonding or micro-cracking, which ultimately result in fibre breakage. This is in agreement with findings in the literature 3,26,55 where microstructural analysis of the composites shows plastic deformation of matrix. Because of the constraining effect of surrounding fibres, extra strain is induced in the matrix as seen by the localised strains in the DIC map.…”
Section: Tensile Testsupporting
confidence: 93%
“…Among full field measurement methods, digital image correlation (DIC) has been used in many fields of solid mechanics including determination of stress-strain response and elastic constants , [4][5][6][7][8][9] observation of crack propagation and damage assessment , [10][11][12][13][14][15][16] investigation on residual stress , 3,[17][18][19][20][21][22] static and dynamic damage analysis . [23][24][25][26][27][28] However, the correct determination of mesoscopic deformation of heterogeneous composite materials and the influence of material structure heterogeneity on the tensile and shear strains have not been carefully investigated by this technique.…”
Designing highly stressed offshore renewable energy composite structures (e.g. wind and tidal turbine blades) necessitates characterisation of woven fabric composite under off axial loading. In this work a combined method of finite element analysis, digital image correlation and microscopy is used to assess the effect of ply orientation on the tensile/shear properties and failure modes of woven glass fibre reinforced polymer composites. Full field strain maps obtained by the digital image correlation method were used to evaluate the damage development and the inhomogeneity of strain localisation. The development of finite element models of mechanical test specimens is based on the analysis of micro-mechanical models of representative volume elements using a homogenisation technique in order to calculate the effective orthotropic properties. The agreement between numerically and experimentally calculated strains obtained in the elastic regimes indicates that stress analysis conducted by numerical methods is useful when characterising the effect of ply orientation on mechanical behaviour. Strain measurement conducted by the digital image correlation method indicated that there is a strong relationship between the strain distribution and the microstructure/ply orientation. In addition, it was found that the levels of localised tensile strain are higher than the global strain indicating the structural heterogeneity of the composite material. Finally, microstructural analysis of tension and shear test specimens showed that the main failure modes are de-bonded fibres, fibre pull out, in-plane/inter-laminar shear cracks and delamination.
“…These localised strains are possibly due to the localised plastic deformation of the matrix and micro-damage such as localised de-bonding or micro-cracking, which ultimately result in fibre breakage. This is in agreement with findings in the literature 3,26,55 where microstructural analysis of the composites shows plastic deformation of matrix. Because of the constraining effect of surrounding fibres, extra strain is induced in the matrix as seen by the localised strains in the DIC map.Figure 9.DIC generated normal strain in longitudinal direction (bold-italiceyy) maps showing inhomogeneity distribution for a tensile test specimen with (a) 0°/90° and (b) ±45° fibre orientation, images were registered at applied true tensile strain in y direction of 1.3% and 10%, respectively.…”
Section: Resultssupporting
confidence: 93%
“…These localised strains are possibly due to the localised plastic deformation of the matrix and micro-damage such as localised de-bonding or micro-cracking, which ultimately result in fibre breakage. This is in agreement with findings in the literature 3,26,55 where microstructural analysis of the composites shows plastic deformation of matrix. Because of the constraining effect of surrounding fibres, extra strain is induced in the matrix as seen by the localised strains in the DIC map.…”
Section: Tensile Testsupporting
confidence: 93%
“…Among full field measurement methods, digital image correlation (DIC) has been used in many fields of solid mechanics including determination of stress-strain response and elastic constants , [4][5][6][7][8][9] observation of crack propagation and damage assessment , [10][11][12][13][14][15][16] investigation on residual stress , 3,[17][18][19][20][21][22] static and dynamic damage analysis . [23][24][25][26][27][28] However, the correct determination of mesoscopic deformation of heterogeneous composite materials and the influence of material structure heterogeneity on the tensile and shear strains have not been carefully investigated by this technique.…”
Designing highly stressed offshore renewable energy composite structures (e.g. wind and tidal turbine blades) necessitates characterisation of woven fabric composite under off axial loading. In this work a combined method of finite element analysis, digital image correlation and microscopy is used to assess the effect of ply orientation on the tensile/shear properties and failure modes of woven glass fibre reinforced polymer composites. Full field strain maps obtained by the digital image correlation method were used to evaluate the damage development and the inhomogeneity of strain localisation. The development of finite element models of mechanical test specimens is based on the analysis of micro-mechanical models of representative volume elements using a homogenisation technique in order to calculate the effective orthotropic properties. The agreement between numerically and experimentally calculated strains obtained in the elastic regimes indicates that stress analysis conducted by numerical methods is useful when characterising the effect of ply orientation on mechanical behaviour. Strain measurement conducted by the digital image correlation method indicated that there is a strong relationship between the strain distribution and the microstructure/ply orientation. In addition, it was found that the levels of localised tensile strain are higher than the global strain indicating the structural heterogeneity of the composite material. Finally, microstructural analysis of tension and shear test specimens showed that the main failure modes are de-bonded fibres, fibre pull out, in-plane/inter-laminar shear cracks and delamination.
“…6–8 AE signals are highly sensitive toward microcracks and thus have gained attention as an effective NDT method. 9–11 The signals (i.e. cumulative hit number) increase markedly near the final failure; this can be used as an indicator of integrity.…”
This study examined the change in acoustic emission as a function of measurement position of fiber-reinforced composites. Single-edge-notched carbon fiber/epoxy composites were prepared and tested under cyclic loading, with sensors located at specific distances from the end of the notch. Although the I b-value increased overall, the degree of increase significantly varied with position and acoustic emission frequency. Notably, the proportion of acoustic emission signals for each failure mode varied due to a high attenuation rate at high frequencies, which increased the I b-value. Accordingly, the high-frequency fiber-failure signals significantly affected the I b-value. This study focused on the importance of analyzing acoustic emission signals by considering the crack location and frequency-dependent attenuation rate. We concluded that an acoustic emission sensor should be located 20–40 mm from the crack location for woven carbon fiber/epoxy composites.
“…Abouhussien et al [29] used AE technology to evaluate the compressive strength gain of concrete with different supplementary cementitious materials, finding that the strength gain rate of concrete is directly related to the AE parameters studied. Ali et al [30] studied the damage evolution of carbon fiber reinforced composites under bending loads, proving the effectiveness of AE in damage determination by scanning electron micrographs. Hakeem et al [31] used AE signal strength to predict the occurrence of cracks in beams.…”
Generally, reactive powder concrete (RPC) contains steel fibers often exposed to aggressive environments. Steel fibers in such RPCs are subjected to corrosion in-service, which can significantly change the mechanical properties of the structural components. In this paper, basalt fibers were used to replace steel fibers for preparing a new basalt fiber modified reactive powder concrete (BFRPC). The bending resistance of BFRPC beams was studied, and the crack propagation and failure type of BFRPC beam were monitored by acoustic emission (AE). During the bending test, the failure type of BFRPC was evaluated by AE. Besides, the effects of notch and interfacial damage on the bending resistance and failure type were also studied. During the test, ordinary Reactive Powder Concrete (RPC) without basalt fibers was used as a reference. Results revealed that failure type of the RPC beam and BFRPC beam was mainly caused by shear failure. The notch increased the number of tensile cracks in the beam failure crack, resulting in a decrease in the bending resistance of RPC beam and BFRPC beam. Besides, basalt fiber could improve the toughness and bending resistance of BFRPC beam and increase resistance of the BFRPC beam to notch and interface damage.
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