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The in-plane load-bearing capacity of marine composite plates is an area that has received little attention, in contrast to the significantly larger buckling and post-buckling studies available on aeronautical composites. The aim of this study is to investigate experimentally the strength to failure of large woven composite panels and correlate the results with finite element analyses. The tests performed were able to demonstrate the well-known sensitivity of the panels to boundary conditions and panel imperfection size, which is also reflected in a parametric study carried out in Abaqus/Standard. Two-dimensional stress-based failure criteria were implemented via a user-defined field (USDFLD) subroutine to detect matrix and fiber damage, which allows progressive damage to be modeled. A modification of Hashin’s failure criteria proved to be the most effective in capturing both the size and location of the damage and obtain a good approximation of the load—displacement history and surface strains. [ABSTRACT FROM AUTHOR]

This study has been designed to experimentally assess the changes of buckling loads of the E-glass fiber/epoxy composite laminates impacted at different impact energy levels. With the experiments conducted, the effects of the geometry parameters such as the ratio of impact point to the length of buckling (G = y/L) have been examined. According to the results of the experiments made, when the ratio of impact position is 0.2, buckling behaviors of the impacted specimens made at the energy levels of and under 10 J have been determined to be almost the same as the buckling behaviors of the non-impacted specimens. Generally, it has been found out that buckling behaviors of the impacted specimens made at the energies under such levels of energy as 15 J increase with the impact point ratio, and when the ratio is 0.2, buckling behaviors have been observed to be maximum. [ABSTRACT FROM AUTHOR]

Explicit expressions are developed for the buckling analyses of rectangular (long) plates: for 'linearly varying axial load' the known results for hinged supports are corrected and new results are presented for built-in and constrained edges; for 'shear load' new results are presented for constrained edges; for 'uniform compression' new results are presented when the longitudinal edges are rotationally constrained by stiffeners. The results are based on the Rayleigh-Ritz method. [ABSTRACT FROM AUTHOR]

A novel approach to the optimization of flexible columns against buckling is presented. The problem of determining the shape of the column that has possibly the largest critical buckling load of columns of a given length and volume is solved for composite materials. The objective of this study was to develop and design an optimized composite column against buckling. Determining what shape of column has the largest possible buckling load of composite column of a given length and volume was considered. Clamped-clamped supported column is an important limit case because it caused debate in many publications. Moreover, in this study, the optimization problem of the clamped-clamped column under buckling load, which was previously dealt with by Tadjbakhsh and Keller [5], Olhoff and Rasmussen [6] and Masur [7] is reinvestigated. It is also proved that the solutions of Tadjbakhsh and Keller, Olhoff and Rasmussen and Masur are not optimum for columns with clamped ends. The present model formulation considers columns for which crush is taken into account in the formulation of the column optimization problem, allowing for bimodal optimum solution. This leads to the necessity for both stability and crush criterion formulation of the optimization problem. The new proposed optimum model solution has been verified with numerical analysis using ANSYS and experimental data for columns with clamped-clamped ends. It was shown that the new proposed model was given the optimum solution for the clamped-clamped case. Detailed results are presented and discussed for clamped-clamped columns having circular cross-sectional configuration. As a result of this study, it was shown that results obtained in previous studies of variation optimum cross-sectional area for columns under compressive forces clamped-clamped ends were erroneous. The corrected optimum form was obtained and results checked by numerical calculations and experimental tests of composite columns. [ABSTRACT FROM AUTHOR]