Fatigue of composite materials is a very complex phenomenon, to date a numerous research effort is being spent on it. Because of deficiencies in study of flexural fatigue performance basalt fiber reinforced polymer (BFRP), the main objective of this work is to investigate the flexural fatigue performance of BFRP. The laminates of 4.0 mm average thickness were fabricated using the vacuum infusion technique. Three different stress levels of (162.90, 122.24, and 81.44) MPa were considered. A failure criterion was considered to be a 20% stiffness reduction of flexural fatigue test. Also, the stiffness reduction zones in the history of fatigue specimen were investigated. The failure mode of specimen at 20% reduction stiffness was inspected. The Weibull distribution function was used to obtain the failure probabilities and scatter. The S–N curve of composite laminates was constructed using five specimens at each number of cycles. This study indicated that under fatigue loading, the stiffness degradation process of composite materials was divided into three stages: the first is the high rate of stiffness degradation at the first few thousand cycles. The second stage then takes place with slow gradual stiffness degradation, which covers a sizeable portion of the component life. Finally, more grave types of damage occur, like fiber fracture, and induce complete material failure.
AbstractIn this study, a thermal buckling analysis of laminate composite square plate was performed with elliptical hole cutout using the finite element method. Graphite/Epoxy laminate plate used in this study is symmetrical stacking sequence plate [(0/90)2]s. This laminate square plate was subjected to temperature loading with clamped support on all edges. Moreover, the parameters considered were fiber orientation (θ), a/b ratio (elliptical hole), elliptical hole inclination (φ), thermal expansion coefficient ratio (α1/α2), and thickness of plates (t). The results showed that as the thermal expansion coefficient ratio changes, the elliptical hole ratio and the elliptical hole inclination have inconsequential effects on the performance of the resistance of laminate composite plates. The maximum values of thermal buckling amplification factor were obtained when the ratio a/b = 1.0, which is a circle cutout,while the minimum values were obtained when the ratio a/b = 0.5, regardless of the thickness of plates. Moreover, the plate with elliptical or circle cutout hole provides about 4% to 9% higher buckling resistance than that of the plate without hole cutout, because when subjected to temperature loading the plate with hole can release stress better than the plate without hole.
Recently, basalt fiber reinforced polymer (BFRP) is acknowledged as an outstanding material for the strengthening of existing concrete structure, especially it was being used in marine vehicles, aerospace, automotive and nuclear engineering. Most of the structures were subjected to severe dynamic loading during their service life that may induce vibration of the structures. However, free vibration studied on the basalt laminates composite plates with elliptical cut-out and correlation of natural frequency with buckling load has been very limited. Therefore, effects of the elliptical hole on the natural frequency of basalt/epoxy composite plates was performed in this study. Effects of stacking sequence (θ), elliptical hole inclination (ϕ), hole geometric ratio (a/b) and position of the elliptical hole were considered. The numerical modeling of free vibration analysis was based on the mechanical properties of BFRP obtained from the experiment. The natural frequencies as well as mode shapes of basalt laminates composite plates were numerically determined using the commercial program software (ABAQUS). Then, the determination of correlation of natural frequencies with buckling load was carried out. Results showed that elliptical hole inclination and fiber orientation angle induced the inverse proportion between natural frequency and buckling load.
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