Glass fiber-reinforced polymer (GFRP) composites are widely used in low-weight constructions. SEM (scanning electron microscopy) in situ experiments of damage growth in GFRP composite under three-point bending loads are carried out. By summarizing the experimental results of three groups of samples with different orientation angles of fibers, the dependence of mechanical parameters on the orientation angles of fibers are analyzed. The regression analysis show that the peak strengths, the elastic strengths and the elastic modulus of the composites decease with the orientation angles of fibers almost linearly. Moreover, the damage growth and meso-scale structure changes in GFRP composites during three-point bending loading are analyzed. scanning electron microscopy (SEM), experiment, GFRP composite, three-point bending, damage growth Citation: Zhou H W, Mishnaevsky Jr L, Brøndsted P, et al. SEM in situ laboratory investigations on damage growth in GFRP composite under three-point bending tests.
Recent research works in the area of experimental and computational analyses of microscale mechanisms of strength, damage and degradation of glass fiber polymer composites for wind energy applications, which were carried out in the framework of a series of Sino-Danish collaborative research projects, are summarized in this article. In a series of scanning electron microscopy in situ experimental studies of composite degradation under off-axis tensile, compressive and cyclic loadings as well as three-dimensional computational experiments based on micromechanics of composites and damage mechanics, typical damage mechanisms of wind turbine blade composites were clarified. It was demonstrated that the damage mechanisms in the composites strongly depend on the orientation angle of the applied loading with the fiber direction. The matrix cracking was observed to be the main damage mechanism for tensile axial (or slightly off-axis axial) loading; for all other cases (off-axis tensile, compressive and cyclic tensile loadings), the interface debonding and shear control the damage mechanisms.
07MnNiMoDR is a widely used quenched and tempered high strength steel in fabrication of low-temperature pressure vessels in China. It can be used at/above −50°C according to the current design specification of GB 150. Some data show that this provision severely underestimates the performance of this material at low temperature, while others indicate that it overestimates the cryogenic performance of this material. In the paper, a series of tests including uniaxial tension tests, impact test and fracture toughness tests were carried out at low temperature to investigate the properties of 07MnNiMoDR with different thickness specimens. Fracture mechanics assessment procedures in API 579-1/ASME FFS-1 (Fitness-For-Service) is adopted to evaluate the low temperature design curve of 07MnNiMoDR, and the fracture toughness is obtained by master curve method (MC method) in the transition region. The results show that 07MnNiMoDR can be classified between exemption curve B and D in current edition of ASME Section VIII, Division 2.
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