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Multiple-Pass Homogenization (MPH) technique is used to derive formulas for equivalent torsional and in-plane shear stiffness properties of sandwich plates with periodic core structures. In the first pass of the MPH, a discrete core structure is homogenized in a principal axis resulting in piecewise constant material properties, based on which the second pass can be analytically processed with respect to macroscopic torsion and in-plane shear modes. Two equivalent shear stiffness properties of periodic core structures, G*cxy and Gcxy corresponding to torsion and in-plane shear, respectively, are conceptually and analytically distinguished from each other. By using the Saint-Venant's semi-inverse method and periodic boundary conditions, analytical solutions of the equivalent shear stiffness are explicitly obtained in the form of Fourier series, which consist of a Voigt-type upper bound term and a correction term. Effects of thickness ratio and core transverse shear stiffness on the two equivalent shear stiffness properties are assessed and discussed. The approximation scheme proposed by this study improves modeling of sandwich structures as orthotropic plates, which is expected to be useful in the practical design and optimization of sandwich structures. [ABSTRACT FROM AUTHOR]

Composite sandwich panels constructed from glass-fiber-reinforced facesheets surrounding both foam-filled and nonfilled honeycomb cores are impacted using a drop-weight impactor at three energy levels and three temperatures. The effects of core material, temperature, and impact velocity on the absorbed energy, peak impact force, and damage mechanisms were studied. The foam-filled samples were subsequently subjected to four-point bend tests to investigate the effect of impact velocity and temperature on the damage tolerance and residual strength of the composites. It was found that the temperature can have a significant effect on the energy absorbed and maximum force encountered during impact, although the effect of the impact temperature on the residual bending stiffness and strength of the composites was mixed. In addition, the nature of the core material greatly influenced the damage mechanisms and impact force transfer in the honeycomb sandwich composites. [ABSTRACT FROM AUTHOR]

Knowledge of edge effects in composite with honeycomb cores is essential for the design of sandwich structures. This paper deals with the measurement of strain by the application of reflection photoelasticity. Because of the geometry of honeycomb cores a classical method by strain gages is inaccurate and unsuitable. The measurements by photoelasticity is compared to an analytical and numerical results. The final aim of this work is to determine the behavior of such structures by the exact knowledge of its mechanical properties deduced in part from edge effect results. [ABSTRACT FROM AUTHOR]

A study was conducted to determine the effect of integral stiffeners on the damage growth and ultimate strength of sandwich panels with impact damage. A total of 18 specimens with IM7/8552 [90/0]s facesheets cocured to 25-mm thick Nomex honeycomb core were impacted and tested in compression. All of the specimens were nominally 152 mm in width and 356 mm in length and were impacted at the center of the front facesheet. Damage growth was monitored via strain gages, and ultimate strength was compared against sandwich panels without integral stiffeners. When the integral stiffeners involved redistributing material in the facesheet, the damage in the resulting thinner facesheet often grew sooner and the ultimate strength was unaltered. When the internal stiffeners involved additional material, damage growth was delayed and the ultimate strength was increased to the point where the ultimate failure initiated away from the impact site. [ABSTRACT FROM AUTHOR]

In the present paper undamaged and repaired honeycomb sandwich beams are modelled using finite elements analysis. Under static loading, the stiffness of the beams was predicted successfully, but the failure load was more difficult to obtain accurately. A quasi-three-dimensional model was best suited to representing the overall deformation pattern of the repaired beams, whereas a two-dimensional plane strain model allowed evaluation of the details of different repair designs. [ABSTRACT FROM AUTHOR]

Explores the alternatives to honeycomb and corrugated core sandwich designs. Provision of inexpensive and comparable performing sub-laminates; Properties of sandwich cores and panels; Development of two-dimensionally curved panels for use in reducing vibration and acoustic noise.