No abstract

The microstructure of a carbon fiber-reinforced ZrC matrix composite, C f /ZrC, manufactured by reactive melt infiltration (RMI) was characterized by optical microscopy, X-ray diffraction, scanning electron microscopy, electron backscattering diffraction (EBSD), and transmission electron microscopy. Characterization results revealed a heterogeneous microstructure typical of composites processed by RMI. The major features that were observed include ZrC single crystals in the matrix, Zr-ZrC eutectic phase, and the fiber/matrix interface. The hardness and modulus of ZrC single crystals and the eutectic phase were determined through micro-and nanoindentation. EBSD studies proved that ZrC matrix grains distribute randomly. Fiber bundle areas were examined and revealed poor intrabundle infiltration. Closer inspection of the ZrC crystals revealed the presence of never-before reported inclusions. Analysis of the inclusions revealed their phase composition and a microstructural formation mechanism outlines their development during processing. The phase composition was proved to be nanosized a-Zr with round or needle-like shape. There are two plausible mechanisms for the formation of the inclusion. One is Int.

In marine construction, ship hulls are subjected to high fatigue stresses due to the impact of waves and their cyclic solicitations. However, fatigue behaviour evaluation of the constitutive materials of hull is based on standard tests. The objective of this study is to take a critical view on the current standard test method set to investigate the fatigue life of cellular foam core material as used in high performance sandwich materials. The highlight of this study is to develop a new geometry of specimen in order to achieve coherence between the actual fatigue life time of the real structure and the one of specimens tested in a controlled laboratory environment. The tested specimen is made out of a high-density foam core and thin glass fabric faces. Moreover, a new test rig of different flexure types, in quasi-static or fatigue loadings on sandwich specimens, was developed and validated.

No abstract