Research On Dynamic Buckling Of Composite Bar Subject To Axial Impact And Buckling Of Laminated Plate Under Static Load

Composite materials are widely used in many fields, such as aviation, spaceflight, cars, architecture, chemical industry, shipbuilding etc, because of their superior strength, stiffness, anti-fatigue, anti-knock, designability and good process over most metallic materials. The buckling of composites structure is always one of hot topics of solid mechanics and concerned by more researchers. Because the methods of solving the problems are different, the results are also different. In present paper, several aspects are investigated in the following:1. The present researches on buckling of composite laminated bars and plates are simply generalized, and the main methods and conclusions are summarized.2. Considering the stress wave, the dynamic buckling of composite bars subject to step load, are investigated on theory. The analytic solution are given, and dynamic critical buckling load is obtained. In the same condition, the dynamic critical load is about 2.5 times of the static one.3. Using ABAQUS6.8, the dynamic buckling of composite bar subject to rigid body and step load are simulated. The time-history curve of logarithmic strain for symmetrical points of top and bottom surfaces of key section of composite bar are obtained, and the bifurcating time and critical buckling load also can be acquired by the strain-time curve. Effect of fiber angle, impact velocity and constrained condition on dynamic buckling of composite bars are also investigated. The results indicate that the buckling time of composite bar decrease gradually with increase of the ply-angle when the rigid mass is at the same speed, and buckling time of composite bar decrease quickly with increase of the impact velocity when the ply-angle is same. When the bar is impacted by step load, the critical buckling load gradually decreases with increase of ply-angle; in the same condition, dynamic buckling time decrease with increase of the step load, and the results of critical buckling load basically consistent with the one obtained by the theory.4. Compressive buckling of laminated plate with a delamination is simulated using ABAQUS 6.8. Effects of sizes, positions, asymmetric and shapes of delamination on the compressive buckling are investigated without the consideration of delamination growth and contact. The results indicate the buckling load of composite plate decreases gradually and mode of plate transits from global buckling to mixed buckling, then to local buckling with increase of the sizes for delamination; the buckling load of composite plate decreases gradually and buckling mode transits from global buckling to mixed buckling, then to local buckling with the depth of delamination close to surface of plate; and when the size and position of delamination are given, the buckling load increases gradually with the delamination close to the ends of plate in asymmetric delamination and the value of Pcr/Po are symmetrical about the position L1/L= 0.5 (1-a/L), then the buckling load is the minimum.5. Cohesive element is set between model interfacial layers and solid element is used for model of laminated plate. Contact constraints are imposed in the regin where initial crack exists. Effects of positions and areas of embedded delamination on compressive buckling and growth of laminate plates are investigated. The results indicate buckling load decreases gradually and growth of delamination weakens with the ply angles increase; buckling load decreases with increase areas of embedded delamination and whether symmetrical angles or not, directions of growth is same when buckling of plate is the local or mixed.