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In the present study, a functionally graded cantilever beam has been analyzed to observe its deformation behavior and stress variations. While the material properties (modulus of elasticity, modulus of rigidity, and density) have been varied along the height of the beam, Poisson’s ratio has been considered a constant. The governing equations have been derived using Hamilton’s Principle in the framework of higher-order beam theory. The derived equations are then simplified to a single equation, which is similar to that of isotropic beams. However, the work is extended to include a few higher-order terms and to study the effect of the incorporation of these terms on the resulting FG beam behavior. The development of a single governing equation for studying the statics and dynamics of an FG beam with the incorporation of higher-order terms is a unique part of the report. The solution of the governing equation is approached using approximate methods; in this work, the B-spline collocation technique is used to arrive at the results. A sixth-order B-spline basis function is used as an approximating polynomial, and the Greville abscissa has been used to generate collocation points. The obtained results have been verified against standard literature to find a satisfactory match. The results include comparative plots for normalized bending and transverse shear stresses, with and without the inclusion of higher-order terms. The results are then extended to study the effect of material index on the deformation and stress behavior of FG beams. The effect of aspect ratio on results is also studied for comparison of various beam theories.

In the present study, a functionally graded cantilever beam has been analyzed to observe its deformation behavior and stress variations. While the material properties (modulus of elasticity, modulus of rigidity, and density) have been varied along the height of the beam, Poisson's ratio has been considered a constant. The governing equations have been derived using Hamilton's Principle in the framework of higher-order beam theory. The derived equations are then simplified to a single equation, which is similar to that of isotropic beams. However, the work is extended to include a few higher-order terms and to study the effect of the incorporation of these terms on the resulting FG beam behavior. The development of a single governing equation for studying the statics and dynamics of an FG beam with the incorporation of higher-order terms is a unique part of the report. The solution of the governing equation is approached using approximate methods; in this work, the B-spline collocation technique is used to arrive at the results. A sixth-order B-spline basis function is used as an approximating polynomial, and the Greville abscissa has been used to generate collocation points. The obtained results have been verified against standard literature to find a satisfactory match. The results include comparative plots for normalized bending and transverse shear stresses, with and without the inclusion of higher-order terms. The results are then extended to study the effect of material index on the deformation and stress behavior of FG beams. The effect of aspect ratio on results is also studied for comparison of various beam theories. [ABSTRACT FROM AUTHOR]

The test technology of fuselage panel subjected to combined load is an important technique for aircraft structure strength research. In order to discover the load characters of the fuselage panel subjected to combined internal pressure and shear load, “D” jig was utilized to simulate the boundary conditions of fuselage panel, the internal pressure load was applied by inflating, the shear load was applied by twisting the single box section, the internal pressure load test, shear load test and combined internal pressure and shear load test were completed. The measured stress is in good agreement with the theoretical result, the test shows that the stress level and stress distribution of the fuselage panel skin of the combined internal pressure and shear load test are the superposition of the stress level and stress distribution of the fuselage panel skin of the internal pressure load test and shear load test. Due to the superposition of the outer normal direction deformation of the fuselage panel under the internal pressure load and the normal direction deformation of the fuselage panel under the shear load, the error between the measured stress and the theoretical result in the combined internal pressure and shear load test is larger than that in the single load test, and the precision of the stress distribution becomes worse. [ABSTRACT FROM AUTHOR]

To study the shear behaviors of jointed rocks reinforced by basalt fiber-reinforced polymer (BFRP) bars and steel–FRP composite bars (SFCBs), we conduct laboratory tests and numerical simulations to analyze the shear strength, shear stiffness, energy dissipation, and bolt failure modes. Our results show that the shear stiffness of the BFRP bolted specimen is lower than that of the specimens bolted by steel bars and SFCBs, but the residual shear strength is higher. SFCB-reinforced jointed rock has the highest peak shear strength, and its residual strength is similar to that of the steel bar bolted specimen. The total energy absorbed by the BFRP bolted specimen is comparable to that absorbed by the steel bolted specimen. When the bolt inclination angle is 60°, the shear strength of the BFRP bar bolted specimens is higher than that of the steel reinforced one. The failure characteristics of BFRP bar bolted rocks can be categorized as resin matrix fracture, resin matrix and fiber shear, and fracture of resin matrix and rocks. The failure modes of the SFCB divided into surface FRP failure and steel bending. Based on numerical results, BFRP bars have larger axial force than conventional bolts, but lower shear stress. The axial stress of the BFRP bar increases as the bolt inclination angle decreases. Moreover, the BFRP bar is more likely to cause shear cracks at the interface between the rock and the bolt. Highlights: Experimental and numerical tests were conducted on the jointed specimens reinforced by Basalt Fiber Reinforced Polymer bar and Steel-FRP composite bar. In terms of shear stiffness and residual shear strength, the jointed specimen reinforced by Basalt Fiber Reinforced Polymer bar and Steel-FRP composite bar differ significantly from steel. The specimens reinforced by Basalt Fiber Reinforced Polymer bar are sensitive to the effect of the bolt inclination angles and have higher shear strengths than conventional bolts at the bolt inclination angle is 60°. The axial force and shear force variation laws of different types of bolts were discovered. [ABSTRACT FROM AUTHOR]

Internal pressure is a severe cyclic load for fuselage structure, and it is important to investigate the fatigue and damage tolerance characters of fuselage panel under internal pressure. Boundary condition simulation of fuselage panel subjected to internal pressure load is challenging, and the quality of the simulation influences the range of transition area and even the stress distribution size in examining area. To investigate the stress distribution of fuselage panel subjected to internal pressure, a new test method is proposed. “D” jig is utilized to simulate the longitudinal boundary conditions of fuselage panel, and “Arch” connectors are utilized to simulate the circumferential boundary conditions. Airtight end-plate is utilized to simulate the end of the fuselage barrel. Test fixture and fuselage panel specimen are designed and manufactured according to the boundary simulation requirements. Tests are conducted based on the proposed method. The test results show that hoop stress and axial stress in transition area are much more lower than in the test area. Hoop stress, axial stress and normal displacement in the test area are consistent with theoretic results. The proposed test method settle for engineering precision requirements and provides reference for configuration-selection tests of fuselage panel subjected to internal pressure load.