Yeong-Moo Yi

Experimental strength of composite sandwich panels with cores made of aluminum honeycomb and foam

Composite sandwich panels with face sheets made of carbon/epoxy fabric and carbon/epoxy uni-directional prepreg were tested. The sandwich cores made by aluminum honeycomb and foam were cured with the face sheet at 180 °C. The aluminum core sandwich failed at the 40% failure strain of the face skin in the compression test. On the other hand, the foam core sandwich failed at the 100% failure strain of the face skin in the compression test. In the case of the aluminium core sandwich, nonhomogenous load distributions and fiber contents may affect the lower failure strain. Therefore, the specific compression strength of the foam core was 72% higher than the compression strength of the aluminum core. Failure mode analysis of sandwich panels made of aluminium honeycomb cores shows that shear failure leads to final failure. However, the specific flexural strength of the sandwich panels with aluminum cores had a slightly higher value than that of the sandwich panels with foam cores. Because the sandwich panel with aluminium cores had higher critical stress for the face wrinkling than the sandwich panel with foam cores due to higher compression modulus of aluminium cores than foam cores.

Fabrication of Lightweight Sandwich Structural Components with Superplastic Forming/Diffusion Bonding Technology

In the present study, design and forming process of fabricating titianium lightweight components are developed with applicaton of superplastic forming and diffusion bonding technology. SPF/DB(Superplastic forming/Diffusion bonding) technology is one of the advanced technologies to reduce production cost and weight and currently applied to aircrafts and space launchers in foreign countries. The present study constructs an analysis model to predict superplastic forming behavior of titanium alloy, which is well known for its resistance to deform. The experimental results show the forming of titanium lightweight sandwich structure is successfully performed from 3 sheets of Ti-6Al-4V. The results demonstrate that the developed technology to process design of SPF/DB by the finite element method can be applied to various types of components.