Transverse cracking under tensile loading in Carbon/BMI (bismaleimide), G40-800/5260, and Carbon/Epoxy, T800H/3900-2, composite laminates with toughened-interlaminar layers is investigated experimentally. Laminate configurations used are [0/90]_s, [0/90₂]_s, [±45/90]_s and [±45/90₂]_s for G40-800/5260, while [0/90]_s and [±45/90]_s for T800H/3900-2. Damage mechanics analysis is used to predict transverse cracking based on both the energy and stress criteria. The present analysis can be used as a characterization method of transverse cracking resistance of a material, which will be helpful in ranking materials.

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The effects of volume fraction and particle size of SiC on fatigue crack propagation behavior in SiC-particulate-reinforced 2024-T6 aluminum alloys were investigated. The volume content of SiC was 0, 10, 20 and 30% with two groups of different particle size respectively. At the same stress intensity range, ΔK, the crack propagation rate, da/dN, decreases with increasing volume fraction of SiC particle. For the same volume fraction, the crack propagation rate in the composite with coarse SiC particle is lower than that with fine particle. The crack opening stress intensity factor divided by the maximum stress intensity factor increases with increasing volume fraction of SiC particles. Reinforcement increased the crack closure. The relationship between da/dN and ΔK_eff/E was almost identical for all materials except coarse particle-reinforced composites. At the same ΔK_eff/E, the crack propagates faster in coarse particle-reinforced composites than in the fine particle-reinforced composites and the unreinforced matrix. The threshold stress intensity range ΔK_th, increases with the volume fraction of SiC particles due to the development of crack closure. The roughness of fatigue fracture surfaces at the threshold also increases with increasing the volume fraction of SiC particle.

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This paper is to show an accurate method to predict thermal deformations of honeycomb sandwich panels having composite skins. First of all, problems of the conventional method with utilizing the laminate theory are pointed out. In order to develop an effective predicting method, a model of a detailed structure of a unit cell of a sandwich panel is developed utilizing the 3-D finite element method. A periodic boundary condition is introduced to the model to represent the repetitive structures of the sandwich panel. The effective elastic modulus of the cell foil is obtained from the result of an out-of-plane compressive test on the honeycomb core. The adhesive between the skin and the core is modeled with considering its shape and quantity. The difference between the CTE according to this model and the actually measured figure is approximately 0.1×10^-6/K. The paper further attempts to explain the anisotropic character of the sandwich panel. The result of the analysis suggests that the direction-dependency of the CTE is underestimated with the fact that the effective elastic modulus at a portion where a ribbon is bonded with another ribbon is different from the effective elastic modulus at a portion where the ribbon is on its own.

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