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The effect of a pulsed laser irradiation (Nd:YVO4, 1064 nm) in air on the surface morphology and chemical composition of silicon carbide and on the adhesion with an epoxy adhesive was investigated. Scanning and transmission electron microscopies, atomic force microscopy, and X-ray photoelectron spectroscopy revealed that the laser treatment reduced the contamination level of the surface and induced the formation of a silica-based nanostructured columnar layer on the SiC surface. The mechanism for the formation of five different microstructural regions is described in this paper. In addition, the formation of a 5-10-nm-thick graphite layer between the oxide layer and SiC was observed. The joining test with Hysol® EA9321 showed that the nanostructured columnar silica layer was completely infiltrated by the adhesive, thus leading to a significant increase in the joined specific area and a mechanical interlocking at the adhesive/substrate interface. Nevertheless, the apparent shear strength of the joined SiC samples slightly decreased after the laser processing of the surfaces from about 42 MPa for lapped SiC to about 35 MPa for laser-nanostructured SiC. The formation of the graphite layer was found to be responsible of the poor adhesion properties of the SiC surfaces modified by the laser radiation.

Silicon carbide (SiC) samples have been joined by a pressureless slurry based method. The CaO–Al2O3 (CA) glass-ceramic joining material has been characterized in term of crystalline phases and thermal and mechanical properties. A torsion test based on miniaturized hourglass shaped specimens has been used as pure shear strength test method for joined ceramic samples. Torsion results are compared to those obtained by a single lap offset (SLO) test in compression on the same joined materials. Pure shear strength of 104 ± 25 MPa has been measured by torsion test, whereas single lap offset gave 36 ± 8 MPa.

The results of an experimental investigation on epoxy-joined silicon carbide tested in shear mode by four different configurations of torsion test are presented and compared to results obtained by asymmetric four-point bending and four different lap tests in compression. All samples have been joined by an epoxy adhesive (Araldite AV119) which is to be considered as a model brittle joining material chosen to obtain several joined samples in a reasonable time. Advantages and disadvantages of each configuration are discussed and compared to results previously obtained with epoxy-joined Carbon/Carbon composites and ceramics tested with the same methods.

The aim of this work was to develop a new joining/repairing material suitable to be easily applied at temperature not exceeding 300°C, in air atmosphere, on large surfaces of SiCf/SiC composites for aerospace applications. The joining/repairing material proposed here is based on a Carbon Fiber-reinforced commercial Adhesive (CFA) where silicon carbide particles were added. Mechanical strength of the joined SiC/SiC was tested before and after heat treatment at the maximum working temperature for these SiC/SiC. Flexural strengths higher than 200 MPa and 90 MPa, before and after heat treatment, respectively, were obtained by coupling mechanical and adhesive bonding techniques.

The present work concerns the assessment of residual stresses (RS) in a component for thermonuclear applications, made by casting of copper on a carbon fibre-reinforced carbon composite and intended to be subjected to severe cycles of thermal, mechanical and neutron loads. The magnitude of RS left at the interface between the two materials in the production process, due to thermal expansion mismatch, has to be carefully assessed. In the present investigation, the likely spatial distribution of the RS has been predicted first using numerical analysis and has been validated experimentally, then, on the basis of the results of indentation tests performed at the micron scale on the metal layer. It is shown that this simple and fast methodology can return reliable results in the present context.