In the present work, an ultrasonic, an induction, and a through transmission laser welding were compared to join carbon fibre reinforced polyetheretherketone (CF/PEEK) composites. The advantages and drawbacks of each process are discussed, as well as the material properties required to fit each process. CF/PEEK plates were consolidated at 395 °C with an unidirectional sequence and cross-stacking ply orientation. In some configurations, a polyetherimide (PEI) layer or substrate was used. The thermal, mechanical, and optical properties of the materials were measured to highlight the specific properties required for each process. The drying conditions were defined as 150 °C during at least 8 h for PEI and 24 h for CF/PEEK to avoid defects due to water. The optical transmission factor of PEI is above 40% which makes it suitable for through transmission laser welding. The thermal conductivity of CF/PEEK is at most 55 W·(m·K)−1, which allows it to weld by induction without a metallic susceptor. Ultrasonic welding is the most versatile process as it does not necessitate any specific properties. Then, the mechanical resistance of the welds was measured by single lap shear. For CF/PEEK on CF/PEEK, the maximum lap shear strength (LSS) of 28.6 MPa was reached for a joint obtained by ultrasonic welding, while an induction one brought 17.6 MPa. The maximum LSS of 15.2 MPa was obtained for PEI on CF/PEEK assemblies by laser welding. Finally, interfacial resistances were correlated to the fracture modes through observations of the fractured surfaces. CF/PEEK on CF/PEEK joints resulted in mixed cohesive/adhesive failure at the interface and within the inner layers of both substrates. This study presents a guideline to select the suitable welding process when assembling composites for the aerospace industry.

While the surface of many ceramic particles is covered by positive and negative species, boron nitride displays no charge on the surface. Nevertheless, the interest in boron nitride is rising: Little materials combine electrical insulation and high thermal conductivity; both properties are required for many applications, for instance, in electronic devices and sensors. Hydroxyl (-OH) groups are usually created on the surface to increase the hydrophilicity of particles. In this work, we compare four treatments to select the one that ~$, increases most significantly the hydrophilicity of hexagonal boron nitride ~~" • • '' '' " "r.!.,~1 " " 00 " n platelets, that is to say, for which the most-OH groups are grafted onto the surface. The treated particles have been studied by SEM, FTIR, and XPS. Our results show that these techniques are not appropriate to probe slight chemical changes. Indeed, hydroxyl groups are more likely introduced on the edges of the platelets. The highest hydroxyl concentration corresponds to 2.4% of boron atoms functionalized. The settling of low concentrated suspensions has been followed by optical visualization. Multiple light scattering was used for high concentrated suspensions. The rheological behavior of stable suspensions in water and isopropanol has been determined by transient flow and dynamic tests. Measuring the viscosity of suspensions appears as a way to evaluate the surface alterations of boron nitride. The method involving thermal treatment is the most efficient to increase the concentration of hydroxyl groups when the particles are suspended in water. The treatment with nitric acid seems to be the most efficient when the particles are suspended in isopropanol. Moreover, the thermal treatment is more environmentally friendly than using strong acids or bases. Hydroxylated particles can be used either as a starting material for further modification such as covalent functionalization or directly to prepare suspensions or polymeric based composites.