Abstract

The present work focuses on the mechanical characterization of polymer matrix composites reinforced with graphene oxide (GO) nanostructures. Firstly, the selection of the polymer matrix, the parameters for performing a proper curing and the fabrication of the composite material are carried out. The proposed procedure results in an adequate dispersion of the GO, without the need for solvents, which positively influences the mechanical properties of the resulting material. The epoxy resin selected as matrix is ​​reinforced with different percentages of GO in order to study the influence of the reinforcement on the apparent mechanical properties. The composites obtained using such nanostructures are characterized by compression and three-point bending testing. Through the use of the Digital Image Correlation (DIC) technique is possible to evaluate the strain state of the material during the tests. This behaviour is combined with the analytical estimations developed to take into account in the results of the bending testing the difference of the tensile and compressive elastic properties of the material. In addition, numerical simulations are developed by applying both the Finite Element Method (FEM) and the eXtended Finite Element Method (XFEM) whose results are used to validate the experimental data and the analytical model.

Abstract

The use of different stereospecific metallocene catalysts: isotactic (iPP, C2-symmetry) and syndiotactic (sPP, Cs-symmetry) has been investigated in order to improve the mechanical properties of polypropylene/nanoclay nanocomposites obtained by in-situ polymerisation. Stereoregular nanocomposites have been synthetized in the presence of polar comonomers (1-undecenol (R-OH) and acid-undecenoic (R-COOH) for improving the matrix-nanoclay chemical compatibility. An important study of variables: amount of nanoparticles used as co-catalyst support, type of catalyst, type and amount of comonomer have been studied in a full factorial design of experiments in order to identify the main factors that achieve a balance between the stiffness and toughness of the polypropylene nanocomposites.

Important results were found from ANOVA (analysis of variance): the nanoclay has a greater influence on the syndiotactic configuration and, the amount of polar comonomer is the main factor in maximising mechanical properties, irrespective of stereospecificity of the polypropylene nanocomposites.

Abstract

In the current work we present a series of nanocomposite materials printed via stereolithography using an acrylic organic matrix together with graphite nanoplatelets (GNP) as inorganic filler. It was generally observed that presence of GNP decreases the mechanical properties with respect to the unmodified resin, probably because the presence of pores around GNP. However, composites containing 2.5 wt% GNP showed electrical resistivity values in the range of 10⁶ Ohm·cm, nine orders of magnitude below unmodified resin. In these conditions we state we have a material with characteristic semiconductive properties.

Abstract

One of the most critical challenges in the aerospace industry is the mismatch in the coefficient of thermal expansion (CTE) between optical components in satellites and their metallic supports, which limits system reliability and performance. Ceramic materials, due to their superior thermal properties, offer a potential solution; however, their adoption has been limited by the complexity of their geometries and conventional manufacturing constraints. Additive manufacturing has opened new opportunities for the development of advanced ceramics, including ceramic matrix composites (CMCs). Within the framework of the AERORECORD-3D project, funded by the Spanish Ministry of Science and Innovation, ceramic cordierite-based supports reinforced with reduced graphene oxide (rGO) have been developed for aerospace applications. In this study, cordierite nanocomposites with varying rGO contents were successfully fabricated via 3D printing. Their thermal, electrical, and mechanical properties were evaluated to assess their performance, exploring their potential as advanced materials for demanding space applications. This work represents a significant step toward the implementation of 3D-printed ceramic nanocomposites by combining innovative materials with advanced additive manufacturing technologies.

Abstract

Cellulose nanocrystals (CNC) have attracted great interest as nanoreinforcement due to their excellent mechanical properties. Furthermore, their dispersibility in water makes them suitable for their incorporation in many aqueous systems such as waterborme polyurethanes (WBPU). WBPUs ​​have gained attention due to their versatility and ability to ajust their properties to a wide range of applications, in addition to their non-toxicity, non-flammability and environmental sustainability. Therefore, in this work a waterborne polyurethane has been synthesized for the preparation of nanocomposites with different contents of cellulose nanocrystals, incorporated by different routes, the classical mixing by sonication once the waterborne polyurethane has been synthesized, and the alternative in-situ by adding the CNCs in water during the WBPU synthesis, just in the phase inversion step. The obtained dispersions have been used in the preparation of films by casting and mats by electrospinning. The films and mats have been characterized from the point of view of their physical-chemical, morphological and superficial properties.

Abstract

The family of polyolefins are materials with a high demand, due to thermoplastics are structurally simpler and economical in their production and processing. Within the polyolefins, the commercial use of polypropylene began with the rise of the catalyzed reactions, in this way it was possible to control its specific conformation and with it, the final properties. In order to improve their properties, these materials are usually reinforced, specially with nanometric loads. So far, three methods have been developed for obtaining nanocomposites: In situ polymerization, melt intercalation and solution mixing. In order to solve the existing problems, in terms of charge dispersion, molecular weight control of the synthesized matrix and the complexity of the immobilization processes of the metallocene catalysts, this research uses In situ polymerization of polypropylene-Sepiolite, using the nanoclay as support of the catalytic system. This study proposes a method of immobilization that contemplates the use of the density of the polar groups that has the surface of Sepiolite, to fix the co-catalyst. In addition, the resulting polymerization process defines the reaction temperature as a variable which will provide a mechanism for controlling the molecular weights of the polypropylene. The proposed method has allowed the polypropylene to be added in its own synthesis process, besides controlling its structure in terms of its stereo-specificity and molecular weight, thus improving its final properties.

Abstract

Bio-polyamide nanocomposites were prepared using the two most viable techniques from the industrial point of view: the melt intercalation process and in situ polymerization. The effect of the synthesis approach and the amount of nanofibre were evaluated in order to check their influence on morphological, thermal and mechanical properties. Regardless of the preparation method, all nanocomposites showed good despersion of nanoclay in polyamide matrix and significant improvements in Young modulus, tensile strenght and heat-distortion temperature were achieved. However, the nanocomposites obtained by in situ polymerization presented higher values since the dispersion of the nanoclay occurs during polymerization, when polymer chains are growing and the viscosity of the matrix is still low.