Abstract:The stress-strain responses and damage initiation/propagation mechanisms of T700G/LM-PAEK, an open-hole carbon-fiber-reinforced thermoplastic were investigated experimentally and numerically. To obtain the mechanical properties necessary for numerical simulations, uniaxial tensile/compressive, double cantilever beam, and end notched flexure tests were conducted. T700G/LM-PAEK was found to have comparable or higher Young’s modulus, strength, and interlaminar fracture toughness relative to thermoset CFRPs with c… Show more
“…As the [0/90]4s laminate, this is due to the fact that 90° plies are progressively damaged in tension but not in compression. In the case of quasi-istropic carbon/epoxy, 30 we found the same result as in the literature, 25 i.e. OHT strength is higher than OHC strength.…”
Section: Application To Structures With Stress Concentrations In Tens...supporting
confidence: 85%
“…24 The model is applied to OHT, OHC, over-height compact tension and compact compression tests to describe the progressive damage. Finally, Shirazu et al 25 studied the case of carbon fiber reinforced thermoplastic laminates on OHT/ OHC specimen experimentally and numerically. Here, extended finite element method (XFEM) model with elastoplastic constitutive law is considered and predict reasonably well the occurrence of kinking mechanism in unidirectional plies on OHC specimens.…”
The failure of laminated composite structures is linked to the numerous mechanisms that can appear during the material degradation phase under loading. The approach proposed here is to use Continuum Damage Mechanics to describe the matrix degradation at the ply scale and a non-local criterion, called Fracture Characteristic Volume (FCV), to predict the failure in the fiber direction. The FCV is a circular cylinder with a thickness equal to that of the ply where it is applied. The criterion is defined by comparing an average value inside the FCV, the stress in the fiber direction for example, to a maximum allowable value. This approach has been validated for the prediction of failure for complex geometries with stress concentrations in tension. The objective of this paper is to study the effectiveness of this criterion on different laminates and concentration types in the case of compression.
“…As the [0/90]4s laminate, this is due to the fact that 90° plies are progressively damaged in tension but not in compression. In the case of quasi-istropic carbon/epoxy, 30 we found the same result as in the literature, 25 i.e. OHT strength is higher than OHC strength.…”
Section: Application To Structures With Stress Concentrations In Tens...supporting
confidence: 85%
“…24 The model is applied to OHT, OHC, over-height compact tension and compact compression tests to describe the progressive damage. Finally, Shirazu et al 25 studied the case of carbon fiber reinforced thermoplastic laminates on OHT/ OHC specimen experimentally and numerically. Here, extended finite element method (XFEM) model with elastoplastic constitutive law is considered and predict reasonably well the occurrence of kinking mechanism in unidirectional plies on OHC specimens.…”
The failure of laminated composite structures is linked to the numerous mechanisms that can appear during the material degradation phase under loading. The approach proposed here is to use Continuum Damage Mechanics to describe the matrix degradation at the ply scale and a non-local criterion, called Fracture Characteristic Volume (FCV), to predict the failure in the fiber direction. The FCV is a circular cylinder with a thickness equal to that of the ply where it is applied. The criterion is defined by comparing an average value inside the FCV, the stress in the fiber direction for example, to a maximum allowable value. This approach has been validated for the prediction of failure for complex geometries with stress concentrations in tension. The objective of this paper is to study the effectiveness of this criterion on different laminates and concentration types in the case of compression.
“…To date, an anisotropic pressure-dependent elastoplastic constitutive law proposed by Sun and Chen 20 and Yokozeki et al 21 has been considered to take into account the nonlinear responses under tensile and compressive conditions. 19,22,23 For the 0°/90°specimens in this analysis, however, the 0°and 90°plies showed a few plasticity deformations from the experimental results as described in the result section. Therefore, in this study, the XFEM analysis was conducted without plasticity deformation.…”
Section: Mesoscale Analysismentioning
confidence: 70%
“…The shear strain at failure of the specimen prepared in this study was relatively small (=5.81 ± 0.30%), resulting in relatively smaller shear strength. Based on the literature, the shear strains of the ±45° specimen for thermoset CFRP (IM7/8552) 32 and thermoplastic CFRP (T700 G/LM-PAEK) 22 were 8.4% and 22.8%, respectively, which are significantly larger than that of the specimen in this study, suggesting that the ±45° specimen prepared in this study exhibited relatively smaller plasticity.Figure 8.Stress-strain curve for NHT tests: (a) 0° specimen and fitting curve using equation (8), (b) 90° specimen, (c) ±45° specimen and (d) 0°/90° specimen and FE analyses.…”
The mechanical properties of open-hole tensile (OHT) specimens made of 3D-printed continuous carbon-fiber-reinforced thermoplastics (CFRTPs) were investigated. The stacking sequence of the OHT specimens were [0/90]2s, and the as-printed specimens possessed higher porosity (15.19%) than conventional fiber reinforced composites. The OHT tests demonstrated that the tensile modulus and fracture strength of the as-printed specimens exhibited 36.7 ± 0.3 GPa and 226.0 ± 9.0 MPa, respectively. To evaluate the effects of voids on the OHT properties, the 3D-printed CFRTPs were hot-pressed, where fiber orientation and porosity (3.41 ± 0.10%) were improved. Additionally, the tensile modulus was increased to 45.1 ± 0.8 GPa, which is 23% higher than the as-printed specimens, even though the fracture strength were comparable or lower than that of as-printed specimens. To validate such OHT properties, a numerical multiscale model was introduced, with a microscale periodic unit cell (PUC) analysis for determining the effective tensile moduli and mesoscale extended finite element method (XFEM) analysis for OHT properties. In the PUC analysis, we considered a two-scale numerical model including a fiber-resin scale with fiber orientation for effective tensile moduli of a CFRTP filament, and filament-void scale for those of a CFRTP laminate. The porosity and fiber orientation were measured by X-ray computed tomography and digital microscopy observations, and the porosity for the 0° specimen were 14.86%. By substituting the effective tensile moduli of the filament-void scale and those of the fiber-resin scale into the XFEM, respectively, the stress-strain responses of the computational OHT models were found to be in good agreement with those of the experimental results of as-printed and hot-pressed CFRTP, respectively. Both the OHT models showed that the Weibull criterion was satisfied without significant delamination at the failure strain, corresponding to the brittle failure mode due to fiber breakage, which agreed reasonably well with the experimental observations.
“…Based on these properties, constant strength beams reduce the number of measurements that need to be evaluated, require less stringent sensor connection locations, and allow for easier and more accurate calibration experiments. The strain values at different locations on the surface of a constant-strength cantilever beam can be expressed as 20 ε=6lFEb0h2.…”
Section: Performance Assessment Of the Cfrp-fbg Sensorsmentioning
We designed a CFRP-FBG sensor with a "sandwich" structure consisting of carbon fiber reinforced polymer (CFRP) encapsulation layers and a fiber Bragg grating (FBG) for strain monitoring of wind turbine blades. This design aims to protect the FBG sensor while maximizing the strain transfer from the CFRP to the FBG sensor. Strain and temperature experiments showed that the linear correlation coefficient of the experimental CFRP-FBG sensor's central wavelength change-strain evolution curve was above 0.9999, and the repeatability error of the strain sensitivity coefficient was 0.1665%, demonstrating high accuracy and repeatability. Meanwhile, CFRP-FBG was tested in full-size turbine blades in operation, during which time they were subjected to millions of dynamic strain cycles and various loading environments. The results of 11 months of monitoring showed that the CFRP-FBG provides real-time, reliable, and highly accurate strain measurements and can meet the needs of long-term blade strain monitoring.
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