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Cellulose nanofibers (CNF) have recently attracted attention as one of the reinforcements for composite materials. However, the same as other nanofibers, CNFs can be easily agglomerated and the nano-level defibration is necessary to obtain their outstanding properties in polymer matrices. To overcome this issue, two major defibration methods, chemical and mechanical defibration have been considered. The chemically-defibrated CNF is expensive and so prevents the practical realization of CNF as general-purpose products. Therefore, the mechanical defibration method by a clean low-cost water jet was focused on. Mechanically-defibrated CNF reinforced epoxy resin matrix (Epoxy-CNF) composite was fabricated via mechanical mixing and the variation of their tensile and flexural properties with different CNF volume fractions was evaluated. The tensile and flexural moduli of the epoxy resin were increased by CNF addition, while the fracture elongation was decreased. The calculated ultimate tensile strength (UTS) and ultimate flexural strength (UFS) of the Epoxy-CNF composites, using the aspect ratio of the agglomerated CNF clusters, indicated the validity of the random dispersion model considering the agglomerated CNF as one whole fiber. It seems that epoxy resin is enhanced by the mechanical interaction when the CNF volume fraction is higher than 0.37 vol.%. [ABSTRACT FROM AUTHOR]

This paper investigates the deformation and failure behaviors of hybrid layered beams consisting of woven carbon fiber-reinforced polymer composite and shape memory polymer layers subjected to flexural loading. The temperature of the shape memory polymer layer was controlled by using electrical resistive heating of the woven carbon fiber-reinforced polymer layers. Three-point bending tests were then conducted on the layered beams, and the variation in the beam flexural stiffness with temperature was examined. The failure characteristics of the layered beams were also studied by microscopic observations of the tested specimens. In addition, a three-dimensional finite element analysis was performed to determine the beam flexural stiffness and the stress states in the layered beams. The predicted flexural stiffnesses were found to be in reasonable agreement with the experimental data, and the stress results were used to better understand and explain the experimental findings on the beam failure. The present results can be useful in the design and developments of high performance material systems with variable stiffness properties for aerospace morphing applications. [ABSTRACT FROM AUTHOR]

This work deals with the delamination growth behavior in woven glass fiber reinforced polymer (GFRP) composite laminates under mixed-mode I/III fatigue loading at cryogenic temperatures. Fatigue delamination tests were carried out with eight-point bending plate (8PBP) specimens at room temperature, liquid nitrogen temperature (77 K), and liquid helium temperature (4 K), and the delamination growth rate data were expressed in terms of the energy release rate range during fatigue loading. The energy release rate was calculated using the three-dimensional finite element method. Moreover, the fracture surface characteristics of the woven GFRP laminates under mixed-mode I/III fatigue loading were examined by scanning electron microscopy (SEM). [ABSTRACT FROM AUTHOR]

This article investigates the interlaminar shear behavior and damage detection of woven carbon fiber reinforced polymer composite laminates at cryogenic temperatures. Short beam shear tests were performed at room temperature and liquid hydrogen temperature (20 K), and the temperature dependence of the apparent interlaminar shear strength was examined. The electrical resistance of the composite specimens was also monitored during the tests. A detailed observation of the tested specimens was made to assess the damage, and the relationship between the damage and the electrical resistance was discussed. In addition, the stress, strain and current density distributions in the short beam shear specimens were determined by the finite element method. The numerical results were used to better understand and explain the experimental findings. [ABSTRACT FROM PUBLISHER]

This study deals with the thermal-mechanical behavior of satin weave carbon fiber reinforced polymer (CFRP) laminates with internal and/or edge cracks and temperature-dependent material properties under tension at cryogenic temperatures. Cracks are assumed to be located in the transverse fiber bundles and extend to the interfaces between two fiber bundles. Young's modulus and stress distributions near the crack tip under combined mechanical and thermal loads are predicted by finite element models that assume generalized plane strain. The effects of residual thermal stresses and cracks on the mechanical behavior of CFRP woven laminates at cryogenic temperatures are calculated, and the numerical results are presented in graphical form. [ABSTRACT FROM AUTHOR]

This article focuses on understanding the Mode II interlaminar fracture and damage behavior of glass fiber reinforced polymer (GFRP) woven laminates at cryogenic temperatures. A four point bend, end notched flexure (4ENF) test is performed at room temperature (RT), liquid nitrogen temperature (77 K) and liquid helium temperature (4K), and an R-curve characterization is conducted for determining the mode II cryogenic fracture properties of GFRP woven laminates. The test configuration is also analyzed by finite element analysis coupled with damage. The damage distributions within the 4ENF specimens are predicted, and the effect of damage on the Mode II energy release rate is examined. This work is the first application of failure criteria (Hoffman criterion and maximum strain criterion) to the description of the R-curve behavior and interlaminar fracture toughness values of woven laminate ENF specimens at cryogenic temperatures. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and analytical investigation of the effect of specimen geometry on the tensile properties and damage behavior of glass fiber reinforced polymer woven laminates at cryogenic temperatures. Cryogenic tensile tests were performed on three types of specimens, and acoustic emission monitoring was employed to characterize the damage development during loading. A two-dimensional finite element analysis was also carried out for three tensile test specimens in order to have a thorough understanding of the progressive failure behavior. A comparison was made between simulation and experiment. [ABSTRACT FROM AUTHOR]

The severe acute respiratory syndrome coronavirus (SARS-CoV-2) has spread rapidly around the world. In order to prevent the spread of infection, city blockades and immigration restrictions have been introduced in each country, but these measures have a severe serious impact on the economy. This paper examines the possibility of both harvesting vibration energy and detecting mass by using a magnetostrictive alloy. Few efforts have been made to develop new magnetostrictive biosensor materials. Therefore, we propose magnetostrictive Fe-Co/Ni clad steel vibration energy harvesters with mass detection, and we numerically and experimentally discuss the effect of the proof mass weight on the frequency shift and output voltage induced by bending vibration. The results reveal that the frequency and output voltage decrease significantly as the mass increases, indicating that the energy harvesting device is capable of mass detection. In the future, device miniaturization and the possibility of virus detection will be considered. [ABSTRACT FROM AUTHOR]

Cellulose nanofiber (CNF) has been accepted as a valid nanofiller that can improve the mechanical properties of composite materials by mechanical and chemical methods. The purpose of this work is to numerically and experimentally evaluate the mechanical behavior of CNF-reinforced polymer composites under tensile loading. Finite element analysis (FEA) was conducted using a model for the representative volume element of CNF/epoxy composites to determine the effective Young's modulus and the stress state within the composites. The possible random orientation of the CNFs was considered in the finite element model. Tensile tests were also conducted on the CNF/epoxy composites to identify the effect of CNFs on their tensile behavior. The numerical findings were then correlated with the test results. The present randomly oriented CNF/epoxy composite model provides a means for exploring the property interactions across different length scales. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes an experimental and analytical study on the cryogenic fatigue behavior of glass fiber reinforced polymer woven laminates under Mode I loading. Fatigue crack growth rate tests were performed using compact tension specimens at room temperature, liquid nitrogen temperature (77 K), and liquid helium temperature (4 K). The fracture surfaces were also examined by scanning electron microscopy to correlate with the fatigue properties. A finite element method coupled with fatigue damage was adopted for the extensional analysis. The effects of temperature and loading condition on the fatigue crack growth rates are examined. [Copyright &y& Elsevier]

Highlights: [•] We studied the cryogenic mixed-mode II/III fatigue delamination growth in woven laminates. [•] The resistance to fatigue delamination growth at cryogenic temperatures is higher than that at room temperature. [•] The fracture surfaces show the presence of matrix hackles. [•] The inclined hackles are identified with the mixed-mode II/III delamination growth. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates experimentally and numerically the delamination behavior in woven glass fiber reinforced polymer (GFRP) composite laminates with surface-bonded piezoelectric ceramic actuators under Mode I loading at cryogenic temperatures. The piezoelectric actuators were used to control the delamination behavior in a composite double cantilever beam (DCB) specimen, and tests were performed at liquid nitrogen temperature (77K). The finite element analysis of the DCB specimen with piezoelectric actuators was also carried out using temperature-dependent material properties of both the woven GFRP laminates and the piezoelectric ceramics, and the numerical predictions were compared with the experimental data. The dependence of the Mode I delamination behavior on the applied electric fields and the temperature was examined based on the experimental and numerical results, and the feasibility of piezoelectric control of cryogenic delamination behavior in composite laminates was demonstrated. [Copyright &y& Elsevier]

Abstract: This paper presents a study of the delamination fracture behavior of woven glass fiber reinforced polymer (GFRP) composite laminates under combined Modes II and III loading at cryogenic temperatures. Mixed-mode II/III delamination fracture tests were carried out with six-point bending plate (6PBP) specimens at room temperature, liquid nitrogen temperature (77K) and liquid helium temperature (4K). A three-dimensional finite element analysis was also performed to determine the critical energy release rate at the onset of delamination growth, i.e., fracture toughness, and the dependence of the fracture toughness on the temperature and the mixed-mode II/III ratio was discussed. In addition, scanning electron microscopic observations of the fracture surfaces were conducted to examine the cryogenic fracture mechanisms in the woven GFRP laminates under mixed-mode II/III conditions. [Copyright &y& Elsevier]

Abstract: This paper presents the characterization of crack growth in carbon nanotube (CNT)-based polymer composites under fatigue loading. Fatigue crack growth tests were performed on single-edge cracked plate specimens of CNT/polycarbonate composites at room temperature and liquid nitrogen temperature (77K). An elastic–plastic finite element analysis was also conducted to determine the J-integral range. The crack growth rate data were expressed in terms of the J-integral range, and the effect of nanotube addition on the fatigue crack growth behavior was examined. In addition, possible mechanisms of the crack growth in the nanocomposites are discussed based on microscopic observations of the specimen fracture surfaces. [Copyright &y& Elsevier]

Abstract: The present research examines experimentally and analytically the mixed-mode interlaminar fracture and damage behavior of glass fiber reinforced polymer (GFRP) woven laminates at cryogenic temperatures. The mixed-mode bending (MMB) tests were performed with the improved test apparatus, at room temperature, liquid nitrogen temperature (77K) and liquid helium temperature (4K). The energy release rates at the onset of delamination crack propagation were evaluated for the woven GFRP specimens using both beam theory and finite element analysis. The fracture surfaces were also examined to verify the fracture mechanisms. In addition, the initiation and growth of damage in the specimens were predicted by a damage analysis, and the damage effect on the mixed-mode interlaminar fracture properties at cryogenic temperatures was explored. [Copyright &y& Elsevier]