Tribological investigation of carbon fiber-epoxy composite reinforced by metallic filler layer

334-341This work aims to develop a carbon fiber/epoxy composite reinforced by metal fillers (Copper/Stainless steel) in order to improve the tribological properties. For this, a tribological study has been conducted using a ball-on-disc configuration. The surface of the material has been modified by deposing a layer of metal powder during manufacturing. For a better understanding of the wear mechanisms, the worn surface characteristics have been examined using a scanning electron microscope (SEM). The coefficient of friction and the wear rate under different normal loads have been determined for the filled and unfilled composite. The results obtained revealed an increase of the wear rate with the increase of the applied load. Metallic filled carbon–epoxy showed better wear resistance and friction behaviour under different loads. In fact, microhardness measurement showed that the surface hardness has been greatly influenced by the metal filler. The overall results illustrate the impact of metal powders in the modification of polymer matrix composites surfaces. This method is promising to improve the tribological properties

An experimental study of weave pattern effect on the mechanical and dynamic behavior of composite laminates

The current work aimed at investigating experimentally the weave pattern effects on the mechanical and dynamic behaviors of polymer matrix composite laminates. The laminates composed of three different weave types (plain, satin, and twill) of woven glass fabric and STR Medapoxy epoxy resin were fabricated via vacuum molding. Static bending experiments were applied to determine the influence of the weave pattern on the mechanical characteristics of the samples. The failure behaviors of the samples were also examined by optical and Scanning Electron Microscopy (SEM) analyses. Additionally, Dynamic Mechanical Analysis (DMA) in the temperature range of 25-200 degrees C at 1 Hz frequency was conducted to investigate the dynamic characteristics of the samples. It was found that the samples having satin weave type had the best flexural modulus followed by the plain and twill weaves. However, the twill weave laminates exhibited better storage modulus at glass transition temperature values (T (g)) compared to the others. Also, an increase of 3.3 degrees C in glass transition temperature was observed compared to that of neat resin. This was attributed to the better fiber/matrix adhesion and the lower molecular mobility in the polymer chain by the addition of glass twill fibers

Prévalence de la rétinopathie diabétique et facteurs de risque associés dans la région de RABAT

La rétinopathie diabétique (RD) est une affection dont les complications sont redoutables. A travers notre étude nous évaluerons la prévalence de la rétinopathie diabétique dans la région de Rabat (Maroc), ainsi que ses facteurs de risque.Patients et Méthodes: Il s’agit d’une étude prospective incluant 602 patients âgés de plus de 20 ans connus diabétiques qui ont bénéficié d’un dépistage de la rétinopathie diabétique organisé par le service d’ophtalmologie B de l’hôpital des spécialités de Rabat. Nos patients ont tous eu un examen ophtalmologique complet.Résultats: L’âge moyen de nos patients était de 58,5±11,9 ans. L’ancienneté moyenne du diabète était 10,2±7,6 ans. La prévalence de la RD était de 39,7% (IC à 95%: 35,7-43,4), dont 7% de RD proliférante. La prévalence de la maculopathie diabétique est de 10,2% (IC à 95%: 7,8-12,7). L’analyse statistique a trouvé 2 facteurs de risque associés avec la survenue de la rétinopathie diabétique dans notre contexte: l’ancienneté du diabète (OR:1,09 IC à 95%:1,03-1,14) et l’hypertension artérielle (OR:2,52 IC à 95%:1,21-5,25).Conclusion: La prévalence de la rétinopathie diabétique dans cette population marocaine est de 39,7%. Sa diminution passe par la sensibilisation de la population diabétique en collaboration avec les endocrinologues et les médecins généralistes ce qui permettrait aux ophtalmologistes un dépistage précoce et un meilleur suivi de cette affection

Graphene-based composites for biomedical applications

Over the last decade, the superior properties of graphene have contributed to intensive studies on the fabrication and applications of graphene nanocomposites. Ex-situ homologous recombination and recombination techniques were listed. Because of their remarkable features, including thermal conductivity and high-specific area, graphene and its derivatives have a significant prospective for medical and biological applications, including drug delivery and bio-imaging. The usage of graphene-based nanomaterials is a hot topic in medicinal research. Many research studies have been performed on graphene-based composites, but only a few reviews have been published regarding their applications in the biomedical field and potential risk factors associated with human well-being and the environment. Hence, this review paper aims to provide in-depth information on ongoing knowledge and results about the properties of graphene-based composites. The discovery, developmental methods, structural properties, and synthesis of graphene nanomaterials have been discussed. After a brief description of the most common methods used for fabricating or extracting graphene derivatives, the main steps of graphene-based composite preparation are introduced. Applications of graphene-based composites in drug delivery, medical, and biomedical fields have been addressed. Finally, the future perspectives and challenges associated with the applications of graphene-based composites have been summarized

Enhancing Structural and Thermal Properties of Poly(lactic acid) Using Graphene Oxide Filler and Anionic Surfactant Treatment

Graphene has attracted extensive attention in various fields due to its intriguing properties. In this work, nanocomposite films based on poly(lactic acid) (PLA and PLLA) polymers filled with graphene oxide (GO) were developed. The impact of treating GO with the anionic surfactant dioctyl sulfosuccinate sodium salt (AOT) on the properties of the resulting nanocomposites was investigated. To determine the morphological, optical, and structural properties of the obtained materials, physicochemical analyses were performed, including scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) analysis. Additionally, the thermal properties and wettability of neat polymers and nanocomposites were thoroughly investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and contact angle analysis. It was observed that GO was well dispersed throughout the PLA and PLLA matrix, leading to stronger interface bonding. The results demonstrate that the untreated and treated GO improved the crystallinity and thermal stability properties of the PLA and PLLA. However, the AOT-treated GO has significantly higher performance compared to the untreated GO in terms of crystallinity, melting temperature (increased by ~15 °C), and wettability (the contact angle decreased by ~30°). These findings reveal the high performance of the developed novel composite, which could be applied in tissue engineering as a scaffold