Composites in Aerospace and Mechanical Engineering.

An important step towards improving performance while reducing weight and maintenance needs is the integration of composite materials into mechanical and aerospace engineering. This subject explores the many aspects of composite application, from basic material characterization to state-of-the-art advances in manufacturing and design processes. The major goal is to present the most recent developments in composite science and technology while highlighting their critical significance in the industrial sector-most notably in the wind energy, automotive, aerospace, and marine domains. The foundation of this investigation is material characterization, which offers insights into the mechanical, chemical, and physical characteristics that determine composite performance. The papers in this collection discuss the difficulties of gaining an in-depth understanding of composites, which is necessary to maximize their overall performance and design. The collection of articles within this topic addresses the challenges of achieving a profound understanding of composites, which is essential for optimizing design and overall functionality. This includes the application of complicated material modeling together with cutting-edge simulation tools that integrate multiscale methods and multiphysics, the creation of novel characterization techniques, and the integration of nanotechnology and additive manufacturing. This topic offers a detailed overview of the current state and future directions of composite research, covering experimental studies, theoretical evaluations, and numerical simulations. This subject provides a platform for interdisciplinary cooperation and creativity in everything from the processing and testing of innovative composite structures to the inspection and repair procedures. In order to support the development of more effective, durable, and sustainable materials for the mechanical and aerospace engineering industries, we seek to promote a greater understanding of composites.

Prediction of frequency band gaps in one-dimensional endohedral fullerene and carbon nano-onion chains.

CONTEXT: Acoustics have always played a central role in contemporary engineering, especially in the fields of communication, sensing, and even in more extraordinary applications such as non-invasive high-intensity focused ultrasound surgery. The rapid development of nano-scale-based technologies makes imperative the need for novel acoustic devices that take advantage of nanomaterials as well as their extraordinary physical properties. The successful design of such acoustic components requires the implementation of efficient nanostructures accompanied by fast and accurate modeling. Here, endohedral fullerene and carbon nano-onion one-dimensional nano-chains are explored as possible candidate nanodevices that generate unique frequency band gaps. METHODS: The wave propagation in chains of fullerene-based molecules is predicted by representing them as infinite one-dimensional mass-in-mass chains properly assembled by the use of springs whose coefficients are expressed according to the van der Walls (vdW) atomistic interactions. Based on Bloch's theorem, interesting elastic wave dispersion curves are obtained and illustrated, characterized by distinctive frequency ranges that waves cannot propagate, revealing the unique vibroacoustic behavior of the proposed nano-systems.

Cumulative Fatigue Damage of Composite Laminates: Engineering Rule and Life Prediction Aspect.

The analysis of cumulative fatigue damage is an important factor in predicting the life of composite elements and structures that are exposed to field load histories. A method for predicting the fatigue life of composite laminates under varying loads is suggested in this paper. A new theory of cumulative fatigue damage is introduced grounded on the Continuum Damage Mechanics approach that links the damage rate to cyclic loading through the damage function. A new damage function is examined with respect to hyperbolic isodamage curves and remaining life characteristics. The nonlinear damage accumulation rule that is presented in this study utilizes only one material property and overcomes the limitations of other rules while maintaining implementation simplicity. The benefits of the proposed model and its correlation with other relevant techniques are demonstrated, and a broad range of independent fatigue data from the literature is used for comparison to investigate its performance and validate its reliability.

Fullerene Derivatives for Drug Delivery against COVID-19: A Molecular Dynamics Investigation of Dendro[60]fullerene as Nanocarrier of Molnupiravir.

In this paper, a theoretical investigation is made regarding the possibility of using a water-soluble derivative of C60 as a drug delivery agent for treating Coronavirus disease 2019 (COVID-19). Molnupiravir is chosen as the transporting pharmaceutical compound since it has already proved to be very helpful in saving lives in case of hospitalization. According to the proposed formulation, a carboxyfullerene known as dendro[60]fullerene is externally connected with two molnupiravir molecules. Two properly formed nitrogen single bonds (N-N) are used as linkers between the dendro[60]fullerene and the two molnupiravir molecules to create the final form of the C60 derivate/molnupiravir conjugate. The energetics of the developed molecular system and its interaction with water and n-octanol are extensively studied via classical molecular dynamics (MD) using the COMPASS II force field. To study the interactions with water and n-octanol, an appropriate periodic amorphous unit cell is created that contains a single C60 derivative/molnupiravir system surrounded by numerous solvent molecules and simulated via MD in room conditions. In addition, the corresponding solvation-free energies of the investigated drug delivery system are computed and set in contrast with the corresponding properties of the water-soluble dendro[60]fullerene, to test its solubility capabilities.

Nonlinear Finite Element Analysis of γ-Graphyne Structures under Shearing.

In this study, a nonlinear, spring-based finite element approach is employed in order to predict the nonlinear mechanical response of graphyne structures under shear loading. Based on Morse potential functions, suitable nonlinear spring finite elements are formulated simulating the interatomic interactions of different graphyne types. Specifically, the four well-known types of γ-graphyne, i.e., graphyne-1 also known as graphyne, graphyne-2 also known as graphdiyne, graphyne-3, and graphyne-4 rectangular sheets are numerically investigated applying appropriate boundary conditions representing shear load. The obtained finite element analysis results are employed to calculate the in-plane shear stress-strain behaviour, as well as the corresponding mechanical properties as shear modulus and shear strength. Comparisons of the present graphyne shearing response predictions with other corresponding estimations are performed to validate the present research results.

Design of Laminated Composite Plates with Carbon Nanotube Inclusions against Buckling: Waviness and Agglomeration Effects.

In the present study, a buckling analysis of laminated composite rectangular plates reinforced with multiwalled carbon nanotube (MWCNT) inclusions is carried out using the finite element method (FEM). The rule of mixtures and the Halpin-Tsai model are employed to calculate the elastic modulus of the nanocomposite matrix. The effects of three critical factors, including random dispersion, waviness, and agglomeration of MWCNTs in the polymer matrix, on the material properties of the nanocomposite are analyzed. Then, the critical buckling loads of the composite plates are numerically determined for different design parameters, such as plate side-to-thickness ratio, elastic modulus ratio, boundary conditions, layup schemes, and fiber orientation angles. The influence of carbon nanotube fillers on the critical buckling load of a nanocomposite rectangular plate, considering the modified Halpin-Tsai micromechanical model, is demonstrated. The results are in good agreement with experimental and other theoretical data available in the open literature.

Thermomechanical Behavior of Bone-Shaped SWCNT/Polyethylene Nanocomposites via Molecular Dynamics.

In the present study, the thermomechanical effects of adding a newly proposed nanoparticle within a polymer matrix such as polyethylene are being investigated. The nanoparticle is formed by a typical single-walled carbon nanotube (SWCNT) and two equivalent giant carbon fullerenes that are attached with the nanotube edges through covalent bonds. In this way, a bone-shaped nanofiber is developed that may offer enhanced thermomechanical characteristics when used as a polymer filler, due to each unique shape and chemical nature. The investigation is based on molecular dynamics simulations of the tensile stress-strain response of polymer nanocomposites under a variety of temperatures. The thermomechanical behavior of the bone-shaped nanofiber-reinforced polyethylene is compared with that of an equivalent nanocomposite filled with ordinary capped single-walled carbon nanotubes, in order to reach some coherent fundamental conclusions. The study focuses on the evaluation of some basic, temperature-dependent properties of the nanocomposite reinforced with these innovative bone-shaped allotropes of carbon.

Thermomechanical Response of Fullerene-Reinforced Polymers by Coupling MD and FEM.

The aim of the present study is to provide a computationally efficient and reliable hybrid numerical formulation capable of characterizing the thermomechanical behavior of nanocomposites, which is based on the combination of molecular dynamics (MD) and the finite element method (FEM). A polymeric material is selected as the matrix-specifically, the poly(methyl methacrylate) (PMMA) commonly known as Plexiglas due to its expanded applications. On the other hand, the fullerene C240 is adopted as a reinforcement because of its high symmetry and suitable size. The numerical approach is performed at two scales. First, an analysis is conducted at the nanoscale by utilizing an appropriate nanocomposite unit cell containing the C240 at a high mass fraction. A MD-only method is applied to accurately capture all the internal interfacial effects and accordingly its thermoelastic response. Then, a micromechanical, temperature-dependent finite element analysis takes place using a representative volume element (RVE), which incorporates the first-stage MD output, to study nanocomposites with small mass fractions, whose atomistic-only simulation would require a substantial computational effort. To demonstrate the effectiveness of the proposed scheme, numerous numerical results are presented while the investigation is performed in a temperature range that includes the PMMA glass transition temperature, Tg.

Vibration Analysis of Carbon Fiber-Graphene-Reinforced Hybrid Polymer Composites Using Finite Element Techniques.

In this study, a computational procedure for the investigation of the vibration behavior of laminated composite structures, including graphene inclusions in the matrix, is developed. Concerning the size-dependent behavior of graphene, its mechanical properties are derived using nanoscopic empiric equations. Using the appropriate Halpin-Tsai models, the equivalent elastic constants of the graphene reinforced matrix are obtained. Then, the orthotropic mechanical properties of a composite lamina of carbon fibers and hybrid matrix can be evaluated. Considering a specific stacking sequence and various geometric configurations, carbon fiber-graphene-reinforced hybrid composite plates are modeled using conventional finite element techniques. Applying simply support or clamped boundary conditions, the vibrational behavior of the composite structures are finally extracted. Specifically, the modes of vibration for every configuration are derived, as well as the effect of graphene inclusions in the natural frequencies, is calculated. The higher the volume fraction of graphene in the matrix, the higher the natural frequency for every mode. Comparisons with other methods, where it is possible, are performed for the validation of the proposed method.