Aerospace Engineering Structures Research Articles

Mechanical Shock Wave Suppression Structure in Hold-Down and Release Apparatus of Spacecraft

A lightweight and compact structural solution for mechanical shock suppression in spacecraft, such as the hold-down and release apparatus of satellites, is a critical and thorny issue. In this work, a ring-shaped structure is introduced to isolate mechanical waves within cylindrical shells. The underlying mechanism is that the ring-shaped structure undergoes different forms of deformation to counteract different modes of incident waves. A subwavelength Mn-Cu alloy ring is designed as a shock wave barrier in a typical spacecraft hold-down and release apparatus structure with multimodal wave excitation. We experimentally reveal that the Mn-Cu alloy ring reduces the peak value of the acceleration frequency response by 53.4% within a wide frequency range from 1 to 10 kHz. Meanwhile, in the time domain, the instantaneous acceleration peak can be weakened by 37.9%. This work provides a new strategy for shock control of shell structures in aerospace engineering and related fields.

Dynamic modeling and vibration suppression evaluation of composite honeycomb hemispherical shell with functional gradient protective coating

The vibration reduction performance of composite honeycomb hemispherical shells (CHHSs) coated with functional gradient protection coating (FGPC) are investigated in this work. Using the first-order shear deformation theory and the power-law distribution rule, the virtual spring technique, the regional decomposition method, and the Newmark-Beta approach, etc., a dynamic model of the FGPCCHHSs under base excitation is formulated to solve the inherent characteristics and displacement responses in time and frequency domains. After a set of convergence analyses are completed to ascertain an appropriate segment number and the stiffness values of virtual springs employed in the predictive model, the forecasted vibration parameters are verified using the literature and experimental results that are performed on uncoated and coated shells. The maximal natural frequency errors of the current model compared to the experimental results are 3.8% and 4.8%, and the displacement response errors under different excitation amplitudes are less than 10.3% and 12.7%, respectively, which demonstrate the correctness of such a model. Finally, the impact of key structural and material parameters on the vibration behaviors of the FPGCCHHSs is evaluated. To improve their vibration suppression capability, it is recommended to choose a high gradient index of coating material and a large thickness ratio of the FGPC to the overall shell with a reasonable moduli ratio of Material A to Material B of the FGPC to improve vibration reduction capability. This study offers a practical model tool and several important design recommendations for vibration prediction and dynamic attenuation of honeycomb sandwich hemispherical shell structures in aerospace engineering.

Simulation and experimental research on longitudinal-torsional ultrasonic vibration drilling of CFRP/Ti laminates

Carbon fiber reinforced polymer (CFRP) and titanium alloy (Ti) laminated materials are extensively employed as primary load-bearing structures in aerospace engineering due to their exceptional characteristics. During the drilling process of CFRP/Ti laminates, issues like delamination and burr formation significantly impede the overall performance of these laminates. The finite element simulation was carried out to address above challenges using longitudinal-torsional ultrasonic vibration drilling (LT-UVD) of CFRP/Ti laminates. A three-dimensional solid model of CFRP/Ti laminates was developed using the ABAQUS custom VUMAT subroutine interface. A cohesive element was skillfully incorporated into the model to simulate delamination defects in the CFRP material effectively and to elucidate the material damage trends and stress distribution throughout the drilling process of laminated materials. The results obtained from the finite element simulation are meticulously compared with experimental data, revealing a consistent trend in the axial force curve. The simulated axial force’s peak value is 14.45% lower than the peak value obtained from experimental observations. The findings of this research substantiate the efficacy of the developed finite element model for LT-UVD of CFRP/Ti. The model successfully predicted the changing trend of axial force and layered defects during the drilling process. Moreover, it provides a visually intuitive instantaneous cutting state and stress distribution, imparting valuable insights into the intricate drilling mechanisms involved in CFRP/Ti laminates.

Investigation on bearing capacity and fracture behaviour of the bolt in a flange connection considering multiple load cases

In this study, the bearing capacity and fracture behaviour of the superalloy bolts that are commonly used to connect thin-walled structures in aerospace engineering, are investigated. Various load cases (tension, bending, shear, and torque loadings, as well as any combination thereof) are considered in the bolted connection. First, a bolted connection under combined tension–bending loading is considered. The ultimate load calculated by the finite element analysis is compared with that of the experimental test. A single-bolt equivalent model is proposed to reduce the computational cost of the fracture analysis. The parameters in the Johnson–Cook(J–C) model can be efficiently calibrated using the equivalent model. The bolted connection under combined tension–bending–shear loading is further studied using the modified J–C model. Subsequently, a fastener bolted preload is generated by imposing torque loading on the bolt. The bolt torque–preload relationships obtained by the finite element simulation and different theoretical methods are compared. A failure analysis of bolted connections under combined torque–tension loading is conducted. Finally, an ABAQUS plug-in is developed to achieve parametric modelling and a numerical simulation of bolted connections with preloads and multiple loads.

Space membrane wrinkle analytical model based on piecewise stress field

To meet the requirements of membrane structures in aerospace engineering with high precision and surface accuracy, this paper proposes the wrinkle analytical model based on piecewise stress field, then conducts numerical simulation and wrinkle test to complete comparison and verification. On the basis of the corner wedge field, piecewise stress field, with consideration of the edge effect is put forward and applied to establish wrinkle analytical model by deducing the wrinkle details, including wrinkle amplitude, the radius of the wrinkled zone and the number of wrinkles. In order to validate the model, wrinkle simulation and test are introduced and compared with the analytical model in wrinkle contours and profiles. Furthermore, a series of cases with different design parameters are provided based on the analytical model to perform parametric study, which aims to reveal the effect on membrane wrinkle and guide the design of parameters according to the required wrinkle properties.

A thermal resistance detection of heteromorphic devices using SiC diode’s temperature-sensitive parameters

Certain special-shaped devices, such as traveling wave tubes, can be called hollow cylindrical structures in aerospace engineering and other applications. However, the structural complexity of such devices means that their heat dissipation characteristics cannot be measured directly using conventional techniques. The present work describes a method to directly measure such devices’ thermal resistance by semiconductors’ temperature-sensitive parameters. We prepared a special probe to collect transient temperature response, and the differential structure-function curves were obtained by processing the data using the structure-function method. We demonstrate that this method can effectively characterize cylindrical devices’ thermal resistance and detect differences caused by different processes and structures.

The energy dissipation mechanism of bi-metal Kevlar\ itanium fiber metal laminate under high-velocity impact

Fiber Metal Laminate (FML) is an impact resistant material widely used in marine and aerospace engineering structures that need to withstand impact damage, especially deck and bulkhead structures. To investigate the effect of titanium skin on energy dissipation, a series of ballistic impact experiments were performed on a bi-metal FML in this study. The FML were made of Ti–6Al–4V (TC4) skins and orthogonally woven Kevlar-129 fabric impregnated with E54-epoxy resin. Thus, this FML can be also called as bi-metal Kevlar/titanium FML. In addition, a numerical model based on stress wave theory is proposed to study the energy dissipation mechanism of the bi-metal FML under high-velocity ballistic impact. The residual ballistic velocity of the numerical model is verified by the experimental data in this paper and previous experimental data, showing that the numerical model is a more efficient method to analyze the energy dissipation mechanism of bi-metal FML. According to the numerical results, as the dominant energy dissipation, the perfectly inelastic collision of titanium skins dissipated 43%–62% and 17%–27% of total energy at the high-velocity penetration and ballistic limit, respectively. However, regardless of whether the FML has been penetrated, the compression-shear of Kevlar interlayer dissipated 24%–27% of total energy. Furthermore, the numerical calculations also show that the ballistic limit increases approximately linearly with the relative titanium skin thickness when the front titanium skin of the FML is thicker. Finally, this paper proposes a simple specific energy absorption prediction formula that helps to evaluate the energy dissipation capacity of FML.

Graphene Nanocomposites in Space Sector—Fundamentals and Advancements

Graphene is one of the most significant carbon nanomaterials, with a one-atom-thick two-dimensional nanostructure. Like other nanocarbons, graphene has been used as a polymer reinforcement. This review explores the impact of graphene and graphene-based nanocomposites on aerospace applications. The fabrication and indispensable features of graphene-derived nanocomposites have been considered. Numerous polymers and nanocomposites have been employed for aerospace systems such as reinforced thermosetting/thermoplastic polymers and epoxy/graphene nanocomposites. Moreover, graphene-modified carbon-fiber-based composites have been discussed for the space sector. Aerospace nanocomposites with graphene have been investigated for superior processability, structural features, morphology, heat stability, mechanical properties, flame resistance, electrical/thermal conductivity, radiation protection, and adhesion applications. Subsequently, epoxy and graphene-derived nanocomposites have been explored for heat/mechanically stable aerospace engineering structures, radiation-shielding materials, adhesives, coatings, etc.

Configuration Design and Dynamic Characteristics Analysis for Space Membrane Mechanism Based on Deployable Booms

To meet the requirements of deployable structures in aerospace engineering with light weight and high stiffness, this paper proposes the triangular space membrane deployable mechanism based on deployable booms, then conducts dynamic analysis and multiobjective optimization. The configuration design and mass calculation for the membrane mechanism are carried out, including its unfolding support mechanism and tensioned membrane scheme. With a view to performing the dynamic characteristics analysis and parametric studies, the finite element simulation model of the membrane mechanism, including boom, cable and membrane, is built and validated against test results obtained by Polytec. On the basis of the simulation results, a surrogate model of fundamental frequency is established by adopting the response surface method and applied to multiobjective optimization combined with the mass formula. Then, the optimal dynamic and lightweight design parameters are solved via the genetic algorithm. The results provide an indication to aid with the design and analysis of space membrane deployable mechanisms according to the required properties and space mission requirements.

A Review of Origami-Based Deployable Structures in Aerospace Engineering

Origami is a traditional art form of paper folding that originated in east Asia. In recent decades, the concept of origami has been extensively used to design deployable structures. Due to the strict space and load capacity limitations of the aircraft and spacecraft, the equipment they carried must be deployable and light in weight. The origami-based deployable structures provide the possibility for carrying more aerospace equipment. This paper is an overview of current research on origami-based deployable structures and applications in aerospace engineering, which mainly demonstrates the geometric properties, engineering implementations, advantages, and applications of origami-based deployable structures in aerospace engineering. Some of the latest origami-based space instruments are reviewed to have an insight into their basics and applications.

Structural response of sandwich structures with CFRP face sheets under quasi-static indentation and high velocity impact: An experimental and numerical study

Honeycomb sandwich structures (HSSs) with carbon fibre reinforced polymer (CFRP) composite face sheets are extensively used as light-weight structures in aerospace engineering due to their high strength-to-weight ratio and energy absorption properties. However, the composite face sheets are highly vulnerable to impact loads and cause damage to the structure based on the impact energy. This study investigates the structural response of HSS with CFRP face sheets under quasi-static indentation and a wide range of impact energy: low to high velocity impact. A finite-element model was developed and numerical simulations were carried out at various impact energies, thereby providing deeper insights into the impact dynamics and understanding various damage states such as dent, front face sheet perforation, core damage and rear face sheet penetration. The numerical simulation result was compared with the experimentally tested HSS using a single-stage gas gun under 53.6 J to validate the finite-element model in terms of deformation and damage status. A quasi-static indentation test was conducted and numerically predicted force data under impact test for the complete perforation case was compared to address the dependency of rate of loading. The carbon nanotube (CNT) with various weight percentages (wt%), such as 0.2, 0.4 and 0.6, was added to the matrix system through a vacuum assisted resin transfer technique and experiments were conducted at 79, 107 and 135 J. The impact resistance increases with CNT addition and hence no perforation was recorded for all the test cases of 0.6 wt% CNT addition. The influence of CNT addition on the damage area is more on the bottom face sheet and a 57% reduction in damage area was recorded for the case of 0.6 wt% CNT addition at 135 J impact energy when compared to the neat carbon/epoxy composite.

Accelerated Koiter method for post-buckling analysis of thin-walled shells under axial compression

Due to the high specific strength and stiffness, thin-walled shells are widely used in aerospace engineering structures. However, along with the increase of the structure size or the structure hierarchy, the computational cost of the post-buckling analysis of thin-walled shells would increase sharply and then the imperfection sensitivity analysis would become time-consuming. In this study, an accelerated Koiter method is proposed to improve the efficiency of post-buckling analysis and imperfection sensitivity analysis of thin-walled shells under axial compression. In the framework of the accelerated Koiter method, a single mode Koiter method considering pre-buckling nonlinear behavior is used to reduce the computational time of repeated imperfection analysis, which can accurately predict the effect of the small amplitude imperfection. Furthermore, in order to obtain the expanded point of Koiter method, a Combined Approximation (CA)-based iterative eigenvalue algorithm is constructed to obtain the pre-buckling state in the neighborhood of the bifurcation point and reduce computational cost by the reasonable step length prediction. Finally, the efficiency and accuracy of the proposed method are demonstrated by means of four illustrative examples, including the composite cylindrical shell, the isotropic cylindrical shell, the isotropic conical shell and the hierarchical stiffened cylindrical shell under axial compression.

Nanoindentation Properties and Finite Element Analysis of the Rostrum of Cyrtotrachelus buqueti Guer (Coleoptera: Curculionidae).

This work focuses on the application of nanoindentation measurements and the finite element method for analyzing the mechanical properties of the rostrum of the outstanding driller Cyrtotrachelus buqueti Guer. Nanoindentation tests were carried out to measure the Young's modulus and hardness of the rostrum, with the results for the "dry" samples being 13.886 ± 0.75 and 0.368 ± 0.0445 GPa, respectively. The values for the "fresh" samples showed no clear difference from those of the "dry" ones. Moreover, field observation was conducted to determine the motion behaviors of the rostrum on the weevil. Micro-computed tomography technology was employed to obtain structural information about the rostrum, using 9 µm slices. A real three-dimensional model of the rostrum was created using the MIMICS application. Finally, the mechanical properties of the rostrum were determined by finite element analysis. It was concluded that the rostrum provides an ideal biological template for the design of biocomposite materials and lightweight tube-shaped structures. The properties determined in this study can potentially be applied in different fields, such as in the design of automotive hybrid transmission shafts, helicopter tail drive shafts, robotic arms, and other sandwich structures in aerospace engineering.

High residual mechanical properties at elevated temperatures of carbon fiber/acetylene-functional benzoxazine composite

It is always of great practical significance to develop carbon fiber (CF) reinforced polymer composites with high residual mechanical properties at elevated temperatures for aerospace engineering structures, etc. In this work, the CF reinforced composite based on acetylene-functionalized benzoxazine (AFBEN) was manufactured by the resin transfer moulding (RTM) technology. The mechanical properties at elevated temperatures (150–350 °C) are first and systematically examined for the as-prepared CF/AFBEN composite. Differential scanning calorimetry and rheological characteristics are employed to evaluate the adaptability of AFBEN for the RTM process. Dynamic mechanical and thermogravimetric properties of the CF/AFBEN composite are also investigated to evaluate the thermal stability. The results display that the mechanical strengths of the CF/AFBEN composite exhibit the high residual rates of ca. 90% at 250 °C and over 60% at 350 °C compared to the mechanical properties at room temperature. The fracture mechanisms at room and elevated temperatures are studied and the fracture behavior of the CF/AFBEN composite is shown to transform from fiber-matrix interfacial debonding to resin matrix failure as the temperature increases. Consequently, the as-prepared CF/AFBEN composite show great potentials for practical applications in aerospace engineering structures, etc. due to its high residual mechanical properties at elevated temperatures and the ease of the RTM processing.

Compression twist deformation of novel tetrachiral architected cylindrical tube inspired by towel gourd tendrils

Inspired by the coupling geometrical relations of left-hand (LH) and right-hand (RH) climbing towel gourd tendrils within single branch, innovative chiral architected cylindrical tube is proposed, which can convert axial compression loads into angular rotation deformation. Firstly, two series of tetrachiral cylindrical tube samples with rotation disk on the mirror plane (middle cross-section) are designed, where the numbers of unit cells and tetrachiral nodes radius are different. Secondly, the cylindrical tetrachiral tubes are fabricated with Selective Laser Sintering (SLS) nylon sintering techniques, and in-situ compression tests are performed for studying the relation between axial compression strain and rotation angle of the spinning disk. It is found that the proposed innovative tetrachiral cylindrical tube is able to generate lateral rotation, and linear relation between rotation angle and compression force can be harvested. With the progress of micro- and nano-manufacturing techniques, the proposed tetrachiral cylindrical tube with compression-twist deformation mechanism demonstrates robust mechanical performances for future industrial applications, such as: shape memory morphing structures in aerospace engineering, smart actuators and propellers, smart flexible microelectronics and biomechanical devices.

Structural damage identification: A random sampling-high dimensional model representation approach

Structural damage identification and quantification of damage using non-destructive methods are important aspects for any civil, mechanical and aerospace engineering structures. In this study, a novel damage identification algorithm has been developed using random sampling-high dimensional model representation approach. A global sensitivity analysis based on random sampling-high dimensional model representation is adopted for important parameter screening purpose. Three different structures (spring mass damper system, simply supported beam and fibre-reinforced polymer composite bridge deck) have been used for various single and multiple damage conditions to validate the proposed algorithm. The performance of this method is found to be quite satisfactory in the realm of damage detection in structures. The random sampling-high dimensional model representation-based approach for meta-model formation is particularly useful in damage identification as it works well when large numbers of input parameters are involved. In this study, two different optimization methods have been used and their relative capability to identify damage has been discussed. Performance of this damage identification algorithm under the influence of noise has also been addressed in this article.

Modeling Bistable behaviors in Morphing Structures through Finite Element Simulations

Bistable structures, exemplified by the Venus flytrap and slap bracelets, can transit between different configurations upon certain external stimulation. Here we study, through three-dimensional finite element simulations, the bistable behaviors in elastic plates in the absence of terminate loads, but with pre-strains in one (or both) of the two composite layers. Both the scenarios with and without a given geometric mis-orientation angle are investigated, the results of which are consistent with recent theoretical and experimental studies. This work can open ample venues for programmable designs of plant/shell structures with large deformations, with applications in designing bio-inspired robotics for biomedical research and morphing/deployable structures in aerospace engineering.

Damage assessment of pre-stressed structures: A SVD-based approach to deal with time-varying loading

Vibration-based methods are well-established and effective tools to assess the health state of civil, mechanical and aerospace engineering structures. However, their reliability is still affected by the variability of the features commonly used for damage detection. Environmental effects and changes in operational conditions are the main sources of variability in the structural response. As a consequence, the modal identification used to extract damage sensitive features has to face constricting requirements in terms of signals stationarity and performance accuracy. Moreover, with reference to the damage assessment, large variations of monitored features mask subtle effects due to damage, which remain undetected. This study is conceived to address both these issues by focusing, in particular, on the non-stationarity of the loading conditions of tensioned structures, such as cables and pre-stressed beams. The capability of spectral methods to deal with the modal identification of non-stationary systems is enhanced by a curve-fitting procedure based on nonlinear least squares optimization. Wavelet analysis is applied for comparison and validation of the FFT-based technique. Identified natural frequencies are then used for the damage detection, exploiting the capacity of singular values decomposition to discriminate between damage-related events and the intrinsic non-stationary nature of the structural response. A reduced-order realization of the features set is performed to amplify changes not belonging to measurement variability but deriving from exogenous events, such as damage. The proposed methodology is validated by experimental analyses carried out on beams subjected to time-varying loading conditions in order to simulate the health monitoring of quasi and non-stationary systems.

Coupled piezo-elastodynamic modeling of guided wave excitation and propagation in plates with applied prestresses

Plate-like aerospace engineering structures are prone to mechanical/residual preloads during flight operation. This article focuses on the quantitative characterization of applied prestress effects on the piezoelectrically-induced guided wave propagation, which has been widely used in structural health monitoring systems. An analytical model considering coupled piezo-elastodynamics is developed to study dynamic load transfer between a surface-bonded thin piezoelectric actuator and a prestressed plate. The accuracy of the analytical prediction is evaluated by the comparison with the finite element analysis. Based on the developed model, the load-dependent guided wave signal variation in both time-of-flight and amplitude is determined, and its dependence on loading frequency and host material properties is also discussed. It is found that the guided wave signal variation due to the prestress could be significant under some circumstances. A signal difference coefficient is finally proposed to quantitatively assess the signal variation caused by different prestresses. This study can serve as a theoretical foundation for the development of the real-time piezo-guided wave–based structural health monitoring system in a realistic loading environment.

3352 End Milling of Titanium Alloy with a Textured Ball End Mill

Titanium alloy is increasingly applied to parts and structures in aerospace engineering, marine engineering, bioengineering, etc. because of its superior properties. These days, much smaller and more precise parts are required. However, machining of this alloy is still difficult though many different types of coated tools have been developed. In this paper, ball end mills with four different types of texture (grooves) on the rake face were fabricated by focused iron beam irradiation and changes in cutting forces due to the textures were investigated for realizing better cutting conditions. It was found that the textures on the rake face reduced the coefficient of friction.