Nonlinear buckling and folding analysis of a storable tubular ultrathin boom for nanosatellites

In this work we investigated the stability behavior and the folding capability of an ultrathin tubular composite boom with C-cross section to be used in nanosatellites applications. A nonlinear buckling analysis was performed using the Riks method, adopting a perturbed finite element model to study the influence of the unavoidable geometrical variations of the boom thickness, arising from the composite manufacturing processes, on the stability behavior of the tubular structure. The effect of several levels of geometrical imperfection on the buckling behavior was analyzed. The minimum coil radius that can be used for a safe storage the boom was determined by quasi-static explicit analysis. The boom folding process was considered as formed by two sequential steps, the flattening and the coiling. The stress fields associated with both steps were investigated

Advanced Composite Materials by Resin Transfer Molding for Aerospace Applications

Competitiveness drives the aerospace industries to investigate new technology solutions to address market pressure and high-tech demands. The global objective is to reduce to half the amount of fuel by 2020 and at least 70% less by 2025 with respect to the Boeing 777, one of the most efficient aircraft, which is made entirely of carbon fiber. The weight saving to increase payload and the reductions of the cost/time of the production cycle are imperative targets. For these reasons, aerospace companies, which are traditionally based on the use of metal alloys, have been focusing for past decade on composite materials. The main advantages of composites with respect to metals, that are resistance to corrosion and fatigue and high performance/weight ratios, are a set of qualities for winning the current and future aerospace applications. Obviously, this is possible only through the development of economically competitive technologies. The Resin Transfer Molding (RTM) is one of the most promising technology available today. RTM is capable of making large complex three-dimensional part with high mechanical performance, tight dimensional tolerance and high surface finish. A good design by RTM leads to fabricate three-dimensional near-net-shape complex parts, offering production of cost-effective structural parts in medium-volume quantities using low cost tooling. In addition to these advantages, the problems of the joints, typical of the metal structures, can be eliminated by integration of inserts

Flexible nanocomposites based on polydimethylsiloxane matrices with dna-modified graphene filler: Curing behavior by differential scanning calorimetry

Novel silicone-based nanocomposites with varied elastic properties were prepared by blending standard polydimethylsiloxane (PDMS) with a lower viscosity component (hydroxyl-terminated PDMS) and integrating a graphene nanoplatelets (GNP) filler modified by strands of deoxyribonucleic acid (DNA). The curing behavior of these nanocomposites was studied by dynamic and isothermal differential scanning calorimetry. The activation energies of the polymerization reactions were determined using the Kissinger method and two model-free isoconversional approaches, the Ozawa–Flynn–Wall and the Kissinger–Akahira–Sunose methods. Results show that the complex trend of the curing behavior can be described using the isoconversional methods, unveiling lower activation energies for the nanocomposites with standard PDMS matrices. The role of the DNA modification of graphene on the curing behavior is also demonstrated. The curing reactions of the nanocomposites with the PDMS matrix are favored by the presence of the GNP–DNA filler. PDMS/PDMS–OH blends generate softer nanocomposites with hardness and reduced elastic modulus that can be tuned by varying the amount of the filler

Vibration Control of Innovative Lightweight Thermoplastic Composite Material via Smart Actuators for Aerospace Applications

Piezoelectric actuators and sensors can be incorporated into aerospace structures to suppress unwanted flexible oscillations. These devices need to interact with various passive structures, including innovative materials such as thermoplastic composites, which offer several advantages over traditional options. This study explores the application of a piezoelectric-based vibration control system on a lightweight carbon-reinforced thermoplastic material. Numerical and experimental investigations are conducted to assess the mechanical properties and damping behavior of the composite. As a case study, an equivalent orthotropic shell laminate is developed to facilitate finite element modeling of two composite solar panel structures equipped to a spacecraft. Moreover, an electro-mechanical formulation is implemented to integrate smart actuators and sensors onto the composite hosting structure. Finally, the efficiency of the active vibration control system is assessed when significant vibration perturbations are caused on the panels by rigid–flexible dynamics coupling during agile attitude maneuvers. The results demonstrate the damping factor of the material can be noticeably improved, making the proposed system a promising technological solution for further aerospace applications. © 2023 by the authors

DNA wrapping around MWNTs and graphene: a SERS study

In recent years, carbon nanostructure as nanotubes (CNTs) and graphene are at the centre of a significant research effort due to the strong scientific and technological interest because of their unique physical and chemical properties: large surface area, excellent thermal and electric conductivity, high electron transfer kinetics and strong mechanical strength. Recently, a great attention has been paid to the interaction of DNA with carbon-based nanostructures such as C60, multiwalled-nanotubes (MWNTs), single-walled nanotubes (SWNTs) and graphene. The development of these studies is motivated by a wide spectrum of possible use of these materials e.g. as biosensors, drug delivery agents and diagnosis tools. In this work, we applied surface-enhanced Raman spectroscopy (SERS) to the study of DNA/MWNTs and DNA/graphene systems

Hybrid carbon nanocomposites made of aerospace-grade epoxy showing synergistic effects in electrical properties and high processability

In this work, we investigate the processability and the volumetric electrical properties of nanocomposites made of aerospace-grade RTM6, loaded with different carbon nanoparticles. Nanocomposites with graphene nanoplatelets (GNP), single-walled carbon nanotubes (SWCNT) and hybrid GNP/SWCNT in the ratio 2:8 (GNP2SWCNT8), 5:5 (GNP5SWCNT5) and 8:2 (GNP8SWCNT2) were manufactured and analyzed. The hybrid nanofillers are observed to have synergistic properties as epoxy/hybrid mixtures showed better processability than epoxy/SWCNT, while maintaining high values of electrical conductivity. On the other hand, epoxy/SWCNT nanocomposites present the highest electrical conductivities with the formation of a percolating conductive network at lower filler content, but very large viscosity values and filler dispersion issues, which significantly affect the final quality of the samples. Hybrid nanofiller allows us to overcome the manufacturing issues typically associated with the use of SWCNTs. The combination of low viscosity and high electrical conductivity makes the hybrid nanofiller a good candidate for the fabrication of aerospace-grade nanocomposites with multifunctional properties

AUXHEX – a Kirigami inspired zero Poisson's ratio cellular structure

This work describes the development, manufacturing and testing of a zero Poisson’s ratio PEEK cellular structure (AuxHex) made using Kirigami-inspired techniques. The AuxHex hybrid cell pattern is a combination of cells with different shapes that interlock with each other. This principle can lead to graded honeycombs possessing, in different areas, synclastic as well as anticlastic behavior. The AuxHex samples produced have been tested for flatwise compression according to ASTM standards and the results are compared with a unit-cell-based analytical model. Hexagonal-cell shaped honeycombs were also produced with the same technique and used for direct comparison. The mechanical flatwise properties have been benchmarked against the ones of other experimental PEEK-based cores and commercially available honeycombs. AuxHex samples are found to have higher stiffness compared to other experimental PEEK honeycombs, but lower compared with the commercially available honeycombs. The strength thought, while it is still higher compared to the other experimental PEEK cores, it is comparable with other honeycomb configurations

Lezione su invito al "Corso di Prove Meccaniche" tenuto dall' AIM (Associazione Italiana Metallurgia)

Introduzione ai materiali compositi, applicazioni industriali, prove meccaniche e normativ