bluuebunny/crossref_metadata_2025_split huggingface dataset:
Foreign direct investment (FDI) and environmental quality: Is greenfield FDI greener than mergers and acquisitions FDI?
Authors: Ly‐My Dung , Le Thai‐Ha , Park Donghyun 
Published: October 2023

AbstractEnvironmental sustainability is a key objective of sustainable development. In this connection, there are growing concerns about the environmental impact of foreign direct investment (FDI), even though it is a potentially powerful engine of growth and development in developing countries. In this study, we empirically examine and compare the environmental impact of two different types of FDI, namely greenfield FDI, and mergers and acquisitions (M&A) FDI. Using data from 91 countries in 2005–2020, we find significant differences in the environmental effects of the two different types of FDI. In particular, our empirical results show that greenfield FDI is more harmful to the environment of host countries than M&A FDI. In addition, FDI from emerging markets and developing countries tends to be more harmful to the environment than FDI from developed countries.
Practical Ductile Fracture Criterion Model for Metallic Aerospace Structure Static Strength Evaluations
Authors: Yoshida Tsutomu , Ishida Takuya 
Published: October 2023

Abstract
A practical ductile fracture criterion model is developed, which is well suited for the aerospace structure static strength evaluations using detailed finite element analysis. The model is based on the classical Coulomb-Mohr fracture criterion and extended to handle strength anisotropy commonly present in aerospace structural metal materials through the application of stress linear transformation.
The resulting model (TCM: Transformed Coulomb-Mohr model) employs the model parameter identification procedure which utilizes the well-established statistically based material allowable database like MMPDS. Therefore it is relatively easy to establish a MMPDS-compatible TCM model database covering wide range of aerospace structural materials, which makes it usable for the real-world large scale airframe development projects.
To demonstrate the ductile fracture predictive capability of the TCM model, static strength tests for several structural elements are conducted and evaluated. Comparison of TCM model predictions against the ones by two other approaches, namely traditional design chart methods, and naive FE-based evaluation utilizing von Mises stress and Ftu, clearly shows the superior capability of the TCM model approach.
Post-Buckling Analysis of Stringer-Reinforced Composite Wing Panel by Classical and CUF-Based Finite Elements and Effect of Material and Geometrical Uncertainties
Authors: Cabral Pedro H. , Do Prado Alex P. , Pagani Alfonso , Augello Riccardo , Carrera Erasmo 
Published: October 2023

Abstract
The design of reinforced composite aerospace structures and the choice of safety margins are strongly affected by our predictive capability. The analysis of buckling and many other failure mechanisms require the use of mathematical models able to capture 3D complex internal stress states, which is a major concern in composite laminates and represents a challenge of today structural simulations. In this work, a detailed model to characterize the post-buckling behaviour and the stress state of a stringer-reinforced composite wing panel subjected to uniform compression is proposed. The model under consideration has layerwise capabilities and is based on the Carrera Unified Formulation (CUF). According to CUF, refined structural theories can be formulated automatically as a generalization of the three-dimensional equilibrium equations and by making use of arbitrary expansion of the primary unknowns, which can be either distributed along 1D (CUF beam models) or 2D (CUF plate models) supports.
Depending on the choice of the expansion functions, low- to high-order structural theories can be developed in a unified manner. Particular attention is focused on the effect of material and geometric uncertainties on the characterization of the limit load, bifurcations, post-buckling and failure. The numerical results clearly show the advantages of the proposed method and provide good confidence for further experimental testing to justify the use of opportune models able to predict and mimic the stochastic dispersion.
Characterization of Interlaminar Fracture Energy for Asymmetric Laminates With Residual Thermal Strains
Authors: Giles Andrew , Venkataraman Satchi 
Published: October 2023

Abstract
Hybrid composite laminates or fiber metal laminates (FML’s) with fiber reinforced polymer (FRP) matrix composites reinforced with metal foils have been investigated for improvements in fatigue, impact resistance and bearing strengths. In this study, to measure fracture properties of interface of metal foil with FRP composite lamina, the specimens with laminate layup [012, AF, |SS, AF, 012] were used; where 0 represents a 0-degree IM7/977-3 unidirectional pre preg ply, AF represents 3M™ AF-191 adhesive film, and SS represents a 0.005 inch 304 full hardened stainless-steel layer. The location of the starter crack obtained using a Teflon insert is indicated by “|”.
Although the full laminate is symmetric, the two adherents on either side of the crack plane are not. Further, the presence of the metal (Stainless steel foil) on the surface of one of the adherents leads to warping of the adherents due to the mismatch in the thermal expansion coefficients and asymmetry of the lay-up of the adherent sub-laminates. This paper discusses a method for accounting for composite laminate asymmetry, residual thermal stresses, and various contact conditions over a crack surface to obtain fracture toughness. MATLAB program was developed to determine the necessary equations and calculation steps required for processing fracture toughness, as well as for automating the data reduction process. Utilizing these new calculation methods, estimations of GIIc values from test data with and without thermal corrections for two different adhesive thicknesses were obtained. A comparison showed the corrected method led to 8% to 20% higher GIIc values.
A Compositional Study of Regolith Composites With Carbon Nanotube Additives for Extraterrestrial Construction
Authors: Hoe Andrea J. , Lin Wenhua , Wang Yeqing 
Published: October 2023

Abstract
As extraterrestrial construction becomes an increasingly relevant goal in society, it is crucial to identify materials that balance high mechanical performance and ease of sourcing. One such candidate material, suitable for lunar habitat construction, is lunar regolith in combination with urea. This research aims to develop a novel lunar regolith composite for improved material strength. In this study we explore the relationship between the loading of carbon nanotubes within lunar regolith composites and their resulting modification of mechanical properties and porosity. Previous studies have shown the incorporation of carbon nanotubes in various applications such as fly ash composites, increases mechanical properties of interest for the material. The formulation of the composite material consists of lunar regolith, urea, distilled water, phosphoric acid, and carbon nanotube powder. The results of this study will include an assessment of the compressive strength for specimens containing carbon nanotubes at different weight fractions of 0%, 0.25%, 0.50% and 1.00%. Uniaxial compression tests demonstrate a maximum compressive strength of 5.82 MPa. We were able to achieve a 23% increase in compressive strength with carbon nanotube additives over composites containing no carbon nanotubes. However, space habitats require thorough and repeated testing to protect the lives at stake in these extreme environments. This increase in compressive strength allows the development of such materials and will allow for more freedom within the structural possibilities available in space architecture.
Nonlinear Global/Local Stress and Free-Edge Analysis of Ultra-Thin Composite Deployable Booms
Authors: Augello Riccardo , Pagani Alfonso , Carrera Erasmo 
Published: October 2023

Abstract
The purpose of this work is to propose an innovative global/local approach for the failure onset analysis of deployable composite thin and ultra-thin structures in the nonlinear field. The adoption of this technique allows for the overcoming of the weaknesses related to the commercial calculation codes, which make use of three-dimensional finite elements to capture the local stress field arising within the booms. In this framework, the proposed approach leads to a reduction of computational cost, while keeping a high level of accuracy. This is possible thanks to the Carrera Unified Formulation, which allows for the modeling of higher-order plate elements for the analysis of local critical regions of complex composite assemblies.
In order to show the potentialities of the global/local approach, particular attention is given to the problems that mostly characterize composites, among which those related to free-edge, failure concept and interlaminar continuity of the displacements and shear stresses. The triangular rollable and collapsible boom is considered in this study. The results show a perfect accuracy of the in-plane stress components between the global stress values, evaluated with commercial software, and local distribution evaluated with a refined layerwise model. The description of the out-of-plane components is shown too, along with the failure indeces.
Development of a Bio-Inspired Sweeping Wing Structure by Utilizing the Emerging Materials in Advanced Additive Manufacturing
Authors: Soydas Velda Basak , Peel Larry D. 
Published: October 2023

Abstract
Birds, bats and insects inspired the design of sweeping wing aircraft. Their ability to sweep and fold their wings to sharper angles increases maneuverability and assists in navigating air currents. Aerospace engineers developed the sweeping wing by installing mechanical pivots between wing sections, such as on the F-111, F-14, and MiG-23 fighter aircraft. However, their wing structures require additional heavy components, which decreases reliability, payload capacity and aircraft performance. This conceptual work replaces mechanical parts with lighter, bio-inspired flexible hinges and compliant structures, allowing wing-sweeping up to 60°. The primary objective of this study is to have the skin of an un-swept wing fold at multiple locations into a swept wing with fences, reducing spanwise flow. Mathematical models of a flat wing were developed to create multi-segment rectangular and tapered sweeping wings. Several configurations with three wing segments and segment sweep angles were evaluated. 3D CAD models were developed and 3D printed with flexible, compliant hinges and rigid components. These prototype hinges and sweeping mechanisms held their un-swept and swept shapes in proper configurations without tearing or failure and demonstrated viability. The current work is only for a flat wing. However, future work could expand to a traditional wing cross-section using flexible composites.
Flexural Fatigue Behavior of Sea Water Conditioned Carbon/Epoxy Nanoclay Composites
Authors: Tareq Md. Sarower , Hosur Mahesh , Zainuddin Shaik 
Published: October 2023

Abstract
In this work, the flexural fatigue behavior of carbon fiber reinforced plastic (CFRP) composites with respect to stiffness degradation, fatigue life prediction and 3D damage mode with addition of nanoclay as matrix filler is investigated. Three-point static flexural tests were conducted to measure the elastic modulus and failure strength/deflection of the composites. Load-controlled flexural fatigue tests were performed at different stress levels; 0.9, 0.8, 0.75 and 0.7 times the static strength of the corresponding control and nanophased samples to determine the fatigue life and stiffness degradation, respectively. The fatigue life was reliably predicted by means of combined Weibull and Sigmoidal model. It was found that nanoclay added samples exhibited more than 327% improvement in the mean fatigue life and more than 352% improvement in the predicted fatigue life (Pf = 0.5), compared to the control samples. At 0.7 stress level, all the nanoclay added samples passed the ‘run-out’ fatigue criteria of one million cycles, whereas majority of the control samples failed much earlier. Conditioning (6 months under seawater at ambient temperatures) effect on the fatigue performance of the CFRP samples showed that both control and nanoparticles added samples demonstrated lower fatigue life in comparison with corresponding unconditioned samples.
Nonlinear Model Predictive Control of Urban Air Mobility Aircraft for Vibration Suppression and Trajectory Tracking
Authors: Santos Martins Nunes Jessica , Su Weihua 
Published: October 2023

Abstract
This paper presents the development and simulation of the Nonlinear Model Predictive Controller (NMPC) of a tiltrotor urban air mobility (UAM) aircraft. The free flight of the aircraft is governed by a set of nonlinear rigid-body dynamic equations with multiple tiltrotors and their gyroscopic and inertial effects. As a comparison, a feedback Linear-Quadratic Regulator (LQR) is also designed. The control variables include two rotors‘ spin rates, in addition to the traditional elevator, aileron, and rudder deflections. Both controllers are compared in two cases: level flight for vibration suppression and lateral trajectory path tracking. Even though similar results can be obtained in the vibration suppression with the NMPC and LQR, better performance of the NMPC can be observed in the path-tracking case. Unlike the vibration control case, the nonlinear nature of the aircraft flight dynamics should be accounted for by the controller design to properly track the ever-changing path reference, which is not the case for the LQR. In short, while the NMPC has a higher computational cost, it also demonstrates a much better control performance than the LQR.
The Effect of Oxidation in Environmental Barrier Coatings Subject to Foreign Object Damage
Authors: Hoffman Leland C. , Presby Michael J. , Stokes Jamesa L. , Harder Bryan J. , Salem Jonathan A. 
Published: October 2023

Abstract
Oxidation and foreign object damage (FOD) are two key failure modes for environmental barrier coatings (EBCs). For EBCs with a silicon (Si) bond coat, a thermally grown oxide (TGO) layer forms at the EBC – bond coat interface. The TGO layer is considered the weak interface, and directly influences the life of the EBC. Moreover, FOD has been shown to cause significant subsurface damage resulting in delamination or spallation of the EBC which can occur at the EBC - bond coat interface or the bond coat - substrate interface. The purpose of this work is to investigate the synergistic effects of oxidation and FOD in a ytterbium disilicate (Yb2Si2O7) EBC. FOD testing is conducted on as-deposited and steam oxidized samples at room temperature using a 1.59 mm hardened steel ball projectile. The resulting damage is characterized by optical profilometry and scanning electron microscopy (SEM). Additionally, a quasi-static, mechanical assessment of the EBC bond strength in the presence of a growing TGO is presented.
Effects of Manufacturing Processes on Progressive Damage of Composites
Authors: Meka Sai Krishna , Enos Ryan Scott , Zhang Dianyun 
Published: October 2023

Abstract
The manufacturing processes of composites involve complex and inter-related procedures that span across multiple physics domains and scales. To understand the effects of the manufacturing processes on a composite laminate we perform a progressive damage analysis on the composite. We aim to compare residual stresses that are developed due to the Cure Hardening Instantaneous Linear Elastic (CHILE) model, and residual stresses developed due to a simple temperature drop from the rubbery state to glassy state during the manufacturing of the composite. On the application of mechanical loading after the curing of the composite, we incorporate the smeared crack approach to account for the progressive damage of the composite.
A Combined Finite Element and Machine Learning Approach to Accelerate Calibration and Validation of Numerical Models for Prediction of Failure in Aerospace Composite Parts
Authors: Eskandariyun Amirali , Joseph Ashith , Stere Alexandru , Byar Alan , Fomin Sergey , Kabir Mohammed , Dong John , Zobeiry Navid 
Published: October 2023

Abstract
The need for a large number of costly experimental tests is a major challenge in the certification of composite parts in the aerospace industry. While computational simulation, specifically the finite element method (FEM), can accelerate this process through analysis supported by testing, the time-consuming calibration of composite failure models remains a drawback. This often requires an engineer with years of experience to perform trial-and-error simulations. To address this, an automated machine learning framework has been proposed to simulate and calibrate the failure models of composites in an accelerated and low-cost manner. In this framework, FEM parameters are calibrated using probabilistic machine learning in a step-by-step and targeted approach. The single-edge notch tension (SENT) test was chosen as a case study and simulated explicitly with predefined initial parameters. The result was compared with experiments to calculate the calibration error. Then, Gaussian process regression (GPR) was used in an in-house developed program to automatically select new failure parameters based on initial values and the calibration error in the previous step. The program continues this process until the error becomes negligible. For validation, the calibrated model was used to predict the behavior of a center-notch tension (CNT) test. The presented automated framework provides a robust and reliable calibrated model in a significantly faster manner. It also reduces a substantial amount of computational costs, eliminates the need for high expertise, and saves valuable engineering time.
Truss Topology Optimization With Semidefinite Programming and Parametric Model Order Reduction
Authors: Sanmugadas Varakini , Kapania Rakesh K. 
Published: October 2023

Abstract
The feasibility of a hybrid PMOR-SDP approach, that combines semidefinite programming (SDP) and parametric model order reduction (PMOR) was investigated. When an optimization problem comprises of a linear objective and linear matrix inequality constraints, SDP provides an efficient algorithm for arriving at a globally optimum design. This is achieved by solving a linear systems of equations that simultaneously satisfies the optimality conditions of the primal and dual problems. Weight minimization of a structure subjected to frequency or buckling constraints is amenable to this approach. It is postulated that with the right choice of basis and sufficient reduction in the size of the system matrices defining the problem, the convergence of the SDP problem can be accelerated. To test this idea, the weight minimization of a 200-bar truss, subjected to a frequency constraint, was studied here owing the relative simplicity of the problem. The MOSEK solver was used to solve the linear SDP problem. It was found that the Krylov space containing the second moment provided the best basis set. However, the expected reduction in optimization time was not achieved as this approach did not preserve the sparse nature of the stiffness and mass matrices. Future work will study structure-preserving model order reduction to address this issue.
Effect of Preload on Joint Rotation Constant of Conventional Aerospace Bolted Joints
Authors: Medepalli Varadanam , Kalahasti Kishore Kumar , Popuri Bangarubabu 
Published: October 2023

Abstract
Airframe assembly with axial bolted joints in flange configuration is subjected to combined loading of axial load, bending moment and shear force. Structural Integrity of full-scale airframe assemblies is evaluated by conducting full-scale bend load test and by measurement of Joint Rotation Constant (JRC) at different joints to estimate natural frequencies, mode shapes and global deflections accurately and also to classify the joints. Structural integrity, JRC and class of joints primarily depend on type of joint and its preload. Experiments are carried out on axial bolted joint configurations with Pipe and Airframe sections. Effect of preload on JRC at both joints is studied at different torque levels with increasing bending moment. Reduction in measured JRC is observed with increasing preload at Pipe section as well as Airframe section joints. Measured JRC values at both joints have shown decreasing trend with increasing BM for initial preloads before showing increasing trend for higher preloads. Initially, no variation in measured frequencies of first three modes is observed with increasing preload followed by mild increase before showing no variation again for higher preloads for Airframe section joint. The behavior of JRC at different preloads with increasing bending moment indicates how the modal parameters of the assembly and deflections are expected to behave for various preloads.
Self-Healing of Fatigue Delamination in Thermoset Composites Using Thermoplastic Healants
Authors: Vishe Nilesh J. , Mulani Sameer B. , Roy Samit 
Published: October 2023

Abstract
In this study, fatigue testing under mode-I loading was carried out on double cantilever beam (DCB) specimens, and subsequent healing of the delamination was investigated. Due to the susceptibility of laminated composites to delamination, fatigue delamination is one of the crucial damage modes in laminated composites that may result in catastrophic structural failure. Hence, it is necessary to investigate and quantify the delamination crack growth behavior due to fatigue loading and explore methods to heal the delamination. Therefore, DCB specimens of a carbon fiber-reinforced thermoset polymer (CFRP) composite containing thermoplastic healants were manufactured. The main objective of using thermoplastic healants, i.e., polycaprolactone and shape memory polymer, was to close and then heal the fatigue cracks. In-situ self-healing was achieved by activating macro fiber composite (MFC) actuators bonded to the DCB specimen, where the high-frequency vibration of the actuator provides the heat necessary to close the cracks using thermoplastic healants.
Development of a Test Rig for Improved Estimation of Structural Damping of Wind Turbine Composite Materials
Authors: Brough Euan , Nash David , Kazemi Amiri Abbas Mehrad , Couturier Philippe , Reis Vitor Luiz 
Published: October 2023

Abstract
Material damping affects the vibrational response of composite wind turbine blades, which in turn has an impact on the structural stability and fatigue life of the entire system. Understanding material-level structural damping is crucial for improving the performance and reliability of wind turbines. The present work aims to develop an increased understanding of material-level structural damping and focuses on the development of a rig to reliably quantify energy dissipation properties of candidate wind turbine materials. The novel test rig employs Experimental Modal Analysis (EMA) in a vacuum to improve experimental structural damping characterization of high-modulus materials. The test rig allows for a non-constrained, free-free suspension of a sample which minimizes energy loss mechanisms that can lead to unrepresentative results. Sample excitation methods were also compared, and an automated excitation method was devised. The capabilities of the test rig are presented by the damping extraction of aluminum specimens. The results presented also quantify the component of aerodynamic damping present by comparing EMA with and without the presence of air, for several tests, allowing for the characterization of structural damping.