This study presents a comprehensive evaluation of the thermal performance of an air-supported membrane (ASM) structure equipped with thermal insulation under dynamic seasonal conditions. A hybrid methodology combining eight months of on-site monitoring and validated numerical simulation (using COMSOL Multiphysics 6.1.0) was employed to assess the effectiveness of the insulation system. Real-time inner surface temperature data were recorded on one representative day per month, providing baseline temperature profiles. The numerical model, validated against experimental data, enabled detailed analysis of surface temperature distributions, with and without insulation. Thermal performance was evaluated using two key indices: the Maximum Reduction in Temperature (MRT) and the Time Delay Factor (TF). The results showed that insulation delayed heat transfer by up to 1.2 h and reduced indoor temperatures by nearly 20 degrees C during summer months. Thermal resistance values calculated using ISO and ASHRAE methods demonstrated consistency throughout the year, with the envelope Rvalue ranging from 1.86 to 1.91 m2 & sdot;K/W. A parametric study further quantified the impact of insulation thickness, revealing that thermal resistance increases linearly with thickness but exhibits diminishing returns beyond 100 mm. This research fills a critical gap in literature by offering the first full-scale, long-term thermal assessment of a membrane dome structure. The findings highlight the significance of insulation in stabilizing indoor thermal conditions and optimizing energy performance. Practical benchmarks for insulation thickness and heat transfer mitigation are also established, contributing to the advancement of lightweight, energy-efficient building envelope design.

In 2021, following the launch of the Core Module, large-scale flexible solar arrays were successfully deployed in orbit. However, unexpected bending deformations were observed in the arrays post-deployment. Such deformations can adversely affect retraction performance and may increase the risk of substrate-solarcell circuit damage. Currently, the underlying causes of in-orbit deformation remain unclear. Regarding this, this study establishes a coupled thermal-structural model to investigate the integrated synergistic behavior of the substrate-solarcell multilayer structure and identify the fundamental sources of in-orbit deformation. This work indicates that the mismatch of thermo-mechanical parameters (the coefficient of thermal expansion, elastic modulus, and thickness) among layers induces imbalanced stress under the in-orbit thermal environment, which in turn generates a bending moment about the neutral axis and results in bending deformation. The analytical solution for the in-orbit bending deformation curvature is derived. Subsequently, numerical simulations of the flexible solar arrays are performed, successfully reproducing the observed deformation patterns. To prevent recurrence of similar issues in future related products, two distinct mitigation strategies for reducing in-orbit bending deformation are proposed. The findings of this research are expected to contribute significantly to the advanced design methodology for flexible solar arrays.

Viscoelastic mechanics, a critical branch of solid mechanics, characterizes materials exhibiting time-dependent mechanical responses, manifesting as creep, stress relaxation, hysteresis, and rate-dependent effects. For linear viscoelasticity, the classical Boltzmann hereditary integral model provides a rigorous characterization. However, many materials exhibit nonlinear viscoelasticity, which depends on factors such as temperature, humidity, and stress levels. For nonlinear problems, nearly all current research adopts the Schapery hereditary integral model, which is based on the time-temperature superposition principle (TTSP) and the time-stress superposition principle (TSSP). For certain materials, the TTSP/TSSP assumption proves inadequate. This study develops a generalized double hereditary integral model based on the micro-element method, offering a physically intuitive framework that accurately quantifies the individual contributions of temperature, stress level, and other factors to nonlinear viscoelastic behavior. Besides, to address the challenge of characterizing the normalized attenuation factor in nonlinear viscoelasticity, an innovative curve-scaling method is proposed. This method transforms the unstructured fitting of all curves into a well-defined problem of identifying a few universal parameters. Validation against three benchmark cases demonstrates the model's superior predictive capability. These results provide a novel idea for characterizing nonlinear viscoelasticity in solids, establishing a foundation for subsequent research on failure mechanisms, fracture propagation, and contact behavior.

Photovoltaic modules, which convert solar energy into electricity, have been utilized in various applications such as solar farms and building-integrated systems. However, hailstorms present critical challenges to maintain the high efficiency and structural safety during their operational lifespan. To evaluate the mechanical response of photovoltaic module under hail impact, the hail diameters of 30 mm and 50 mm in relation to the 95th and 99th percentiles of historical hail size distribution were selected to represent normal and extreme conditions. An improved numerical model was established considering the state equation, rate dependent and tension-compression asymmetry as well as the Smoothed Particle Hydrodynamics (SPH) method. The layer-specific stress characteristics are analyzed to investigate the stress evolution between material layers. The results show that the maximum stress under a 30 mm diameter hail exists on the upper and lower surfaces of the glass layer rather than the solar cell layer, since the soft encapsulant layer can absorb and dissipate impact energy to mitigate mechanical response. For the hail diameter of 50 mm, the increasing impact energy exceeds the energy dissipation capacity of the encapsulant layer. Therefore, the maximum stress of about 196 MPa mainly localizes in the solar cell layer and exceeds its ultimate strength. A further parametric analysis demonstrates that the reduction of elastic modulus of the encapsulant layer significantly decreases the maximum stress of solar cell layer by 72%, whereas the increase of encapsulant layer thickness only reduces stress by 21%, indicating that the elastic modulus of the encapsulant layer plays a more dominant role than its thickness in mitigating photovoltaic stress. The layer-specific stress analysis of photovoltaic panels under hail impact can provide insights for designing impact-resistant photovoltaic modules.

The application of stratospheric airships as high-altitude platforms (HAPs) has attracted considerable attention from all over the world. Most of the design schemes are non-rigid airships, and no stratospheric airships of semirigid structures have been reported yet. The structural rigidity and stability of a non-rigid airship are completely maintained by the internal and external pressure difference of the hull, whereas that of a semi-rigid airship is maintained by the collaboration of a rigid skeleton and inflated skins. Therefore, compared with non-rigid airships, the operation of semi-rigid airships is less difficult. However, the manufacturing and assembly of non-rigid airships are still challenging, because the skeleton is required to be large span but ultra-light weight. This paper proposes an innovative assembly method for large carbon fiber reinforced polymer (CFRP) spokes designed for semi-rigid stratospheric airship skeletons. A prototype of 21.3 m in diameter was manufactured for method demonstration. The spoke was mainly consisted of a hoop truss, a hub shaft and 28 x 2 radial tendons. The hoop truss was assembled by 28 identical standard modules to reduce the manufacturing difficulty, then the hub shaft and tendons were mounted on the hoop truss to form the spoke. A synchronized stretching scheme was proposed to guarantee that the deformations of all radial tendons were coordinated. After assembly, the tensions of all tendons were tested based on a non-contact measurement method, and a large tension deviation was observed. Then an adjustment strategy was proposed to optimize the tensions of all tendons, and the maximum deviation decreased from 54.3% to 10.6% after four adjustments.

Single-ply fabric reinforced polymer composites (SpFRPCs) are promising materials for deployable space structures due to their temperature-dependent mechanical properties and large deformation bending capability. Before reaching the operational configuration in space, deployable structures undergo repeated bending during ground-based folding-unfolding tests, stowage and on-orbit deployment. This study investigates the damage introduced by repeated large deformation bending in the rubbery state and the corresponding influences on viscoelastic bending in the glassy state of SpFRPC. Dynamic mechanical analysis identifies the glass transition temperature to be approximately 21.5 degrees C. Accordingly, 10 degrees C and 60 degrees C are selected as the representative glassy and rubbery states for bending experiments. The novel column bending test is employed with a specially designed loading protocol consisting of folding, relaxation, unfolding, and recovery steps. An elastic unidirectional glass fiber-reinforced PEEK composite is tested for comparison. Following repeated loading, microscopic observations reveal kinking and bending damage in the reinforcing fabric, accompanied by a reduction in bending stiffness from 405.4975 to 212.4908 Nmm2 per 1 mm specimen width. The viscoelastic bending parameters are experimentally characterized and implemented into the finite element modeling.

The envelope is a critical component determining the structural strength of airships, with its ultimate strength highly sensitive to temperature variations and exhibiting significant statistical dispersion. However, research on the probabilistic failure modeling of envelope materials, particularly methods applicable to structural-level analysis, remains limited. To address this gap, this study proposes a data-to-failure workflow for flexible Vectran woven composite membranes, integrating artificial neural network (ANN)-based constitutive modeling with probabilistic failure surface construction. Uniaxial and biaxial tensile-to-failure tests were conducted over a temperature range of -80 degrees C to 80 degrees C, with full-field strain distributions captured using the digital image correlation (DIC) method and statistical parameters of strain non-uniformity extracted. Following a finite element (FE)-assisted stress correction, ANN-based response surfaces and interpolated probabilistic failure surfaces were developed. Strain uncertainty was propagated into the stress space via the Monte Carlo (MC) method to quantify failure probability distributions. The trained ANN models were then integrated into FE simulations through a COMSOL external material subroutine, enabling test-data-driven prediction of the envelope structural failure probability. Simulation results demonstrate that the proposed approach effectively captures non-uniform strain distributions and associated failure probabilities. Notably, FE-assisted stress correction shrinks the failure surface, while accounting for strain non-uniformity substantially increases the predicted failure probability.

PTFE-coated fiberglass fabric membrane is widely used in architectural structures, but its mechanical properties and constitutive relationship at highly elevated temperature remain unclear. This paper investigates PTFE membrane and welded seams with widths of 50 mm and 75 mm over a temperature range from 20 degrees C to 250 degrees C. Results show that the base material exhibits stable high-temperature performance. Its ultimate tensile strength decreases by only 12.2-12.6% at 250 degrees C, and the strength retention rate exceeds 87%. In contrast, the strength of welded seams drops significantly after the temperature exceeds 150 degrees C, with a reduction of 59.9-73.0% at 250 degrees C. The failure mode shifts from base material fracture to heat-affected zone failure or weld slip. Microscopic observations reveal that coating loss with a thickness decrease of 31.3%, fiber loosening with a thickness increase of 25.8%, and bonding layer degradation caused by high temperatures are the main reasons for performance deterioration. Based on the weld influence coefficient which should not be less than 0.8, the maximum safe working temperatures for 75 mm welds are 216 degrees C in the warp direction and 130 degrees C in the weft direction. For 50 mm welds, they are 169 degrees C in the warp direction and 82 degrees C in the weft direction. An orthotropic hyperelastic constitutive model considering temperature effects is established. Numerical simulations agree well with experimental results, with R2 greater than 0.9 and relative error of ultimate tensile strength within 11%. This study provides a theoretical basis for connection design and safety assessment of PTFE membrane structures under fire conditions.

The analysis of self-consistent constitutive models or finite element models hinges on the conversion between linear viscoelastic material properties, relaxation modulus, and creep compliance. Current techniques, including numerical collocation using the Prony series expansion and analytical techniques, exhibit significant limitations. These limitations manifest as nonphysical negative terms in the material model, arising from the inversion of ill-conditioned matrices. Additionally, there is a lack of spectral consistency between relaxation and retardation spectra, and the analysis is marred by noisy numerical differentiation. In this paper, the authors propose a direct-term interconversion technique between the relaxation modulus and the creep compliance, formulated in the frequency domain. As a result, the complex interconversion between complex relaxation modulus and complex compliance is achieved in terms of the characteristic frequency associated with the Prony series mode. Algebraic expressions yield retardation strengths, ensuring thermodynamic consistency in the material model (positive material parameters) and spectral consistency between the relaxation and retardation spectra. Therefore, the limitations of current techniques are bypassed by the direct interconversion method. The validity of this method is ensured in the paper by using dynamic mechanical analysis (DMA) results from a carbon fiber-reinforced polymer (CFRP) test piece in two directions and from a Henkel Teroson EP5089 adhesive. Hence, the use of the direct term method in viscoelastic interconversion is ensured to be physically accurate and computationally efficient in predicting the durability of polymeric and composite structures.

The retrofitting of existing stadiums with retractable roof systems presents a complex interdisciplinary challenge, requiring the reconciliation of aged structural capacity with modern performance demands. This paper investigates the engineering design and analysis of a new retractable roof system for the Ningbo (Yinzhou) Tennis Center, a facility originally completed in 2007 and now requiring an upgrade to host higher-tier WTA 500 events. The retrofit is further complicated by increased seismic design requirements and the need to preserve the existing structure. To address these constraints, this study proposes a novel, structurally independent roof system comprising 12 radially deployable units supported by an external single-layer spatial grid and lambda-shaped columns. A multidisciplinary approach integrates structural engineering, mechanical systems, and architectural technology. Key innovations include (1) the selection and detailed modeling of a rack-and-pinion drive mechanism, with a floating engagement design to accommodate dynamic load transfer; (2) a two-stage analytical framework employing both sub-assembly and integrated assembly finite element models to capture the unique mechanical behavior and coupling effects between the new and existing structures; (3) the strategic implementation of circumferential hoop cables to counteract uplift forces and redirect the internal force distribution in the supporting bifurcated columns; and (4) the validation of structural integrity through comprehensive static, stability, and seismic gap analyses, informed by wind tunnel testing. The results demonstrate that the proposed system satisfies all strength, stiffness, and stability criteria under multiple operational states (open, closed, and transitional) and meets the enhanced seismic fortification standards. This research provides a validated theoretical foundation and practical implementation guidelines for this specific stadium retrofit, demonstrating a viable pathway for extending the service life of aging sports infrastructure, with insights that may inform similar urban renewal projects under comparable conditions.

Geometrically structured suture interfaces in natural systems exhibit remarkable mechanical performance, inspiring innovative engineering joint designs. In this study, generalized trapezoidal suture geometries are integrated into Strain-Hardening Cementitious Composite (SHCC) specimens to investigate their mechanical behavior and to guide the development of high-performance joints. Flexural tests were performed on SHCC specimens featuring bio-inspired structured suture joints with geometrically tuned deformation. Key mechanical properties, including flexural strength, ductility, failure modes, and energy absorption, were evaluated to optimize suture geometry. Triangular suture geometries were found to promote uniform stress distribution and superior mechanical performance. Specimen S beta-1A90W1.0 achieved an 18.8% increase in loadbearing capacity and a 6.8% enhancement in energy absorption compared to the unjointed cast counterpart. These results demonstrate that coupling bio-inspired suture interfaces with the strain-hardening characteristics of SHCC enables synergistic enhancements in strength and energy absorption, providing a reliable pathway for designing structurally efficient engineering joints.

Despite continuous advances in concrete technology, its inherently low tensile strength and brittle fracture characteristics have long restricted its application to compression-dominated design paradigms. Robotic additive manufacturing (RAM), endowed with geometric programmability and meso-architected control, enables precise fiber alignment along deposition trajectories, thereby offering an unprecedented opportunity to transcend this long-standing limitation. Yet, the inevitable emergence of weak deposition interfaces unveils a critical, unresolved mechanistic incongruity between the continuity-centered material principle of cementitious systems and meso-architected functionality toward intelligent construction. This study introduces a process-structure-material integrated design strategy based on programmable robotic deposition, embedding the bouligandinspired helicoidal sequence-unattainable through conventional casting-into 3D-printed strain-hardening cementitious composites (3DP-SHCC). Biaxial flexural tests reveal that the bouligand architecture reconfigures interfacial deformation and stress redistribution, thereby enhancing toughness and energy dissipation. Compared with its parallel-printed counterpart, the bouligand-architected specimen exhibits markedly higher flexural strength and energy dissipation, indicating a pronounced architecture-enabled enhancement in strength-toughness performance without altering the material composition or mix design. This work transforms weak deposition interfaces from intrinsic defects into programmable dissipation channels, demonstrating the potential of mesoscale architectural design to enhance energy dissipation in cementitious composites fabricated via RAM, and advancing digital construction strategies-from passive defect mitigation toward bio-inspired mesoscale architectures with programmable functionalities.

Radiative cooling-coated polyvinyl chloride (PVC) membranes offer an effective solution to reduce cooling energy demand in membrane-based buildings. However, PVC membranes as load-bearing components are subjected to significant tensile deformation, which may alter the microstructure of the coating and degrade its spectral selectivity and cooling capacity. In this study, a radiative cooling coating was developed and applied to PVC membranes, and its optical stability and cooling performances under varying uniaxial strains were systematically investigated through macro-scale measurements and micro-structural analysis. It is obtained that uniformly dispersed BaSO4 microparticles enhance Mie scattering, enabling a solar reflectance of 92.4% across 0.3-2.5 mu m. Abundant functional groups contribute to a high mid-infrared emissivity of 93.1% in the 8-13 mu m atmospheric window. With increasing strain, surface roughening and crack formation disrupt scattering paths, resulting in a reflectance reduction to 87.5%, while the chemical structure remains stable and emissivity only slightly decreases to 92.0%. Outdoor tests confirm that unstrained membrane achieves a peak temperature reduction of 12.9 degrees C due to high reflectance and high emissivity. Tensile strain weakens Mie scattering and reduces cooling efficiency, but the coated membrane still achieves a 10.1 degrees C temperature drop until 20% strain. This study reveals the strain-dependent optical and thermal mechanisms of radiative cooling coatings in their application to membrane materials, and provides technical and theoretical support for the performance evaluation and practical utilization of radiative cooling-coated membrane structures.

Flexible solar arrays (FSAs) are utilized as the power supply for spacecraft due to their high power-to-mass ratio. However, on-orbit telemetry data shows that irreversible out-of-plane deformations in FSAs pose severe threats to power generation efficiency and cyclic deployment capability. This study investigates the deformation behavior of FSAs under space thermal cycling environments through experiments and numerical simulations. Multi-cycle thermal cycling tests (-100°C to +100°C) were conducted on FSAs submodule specimens, with surface strain and deformation monitored by 3D digital image correlation (DIC). Results revealed that upon returning to room temperature, the surface of substrate retained a residual strain of 0.12% and an out-of-plane bending curvature of 0.025cm-1. Moisture absorption and dehydration shrinkage tests were executed under room temperature and standard atmospheric pressure, a dehydration shrinkage coefficient of 457.42/%. Furthermore, the thermal expansion and dehydration shrinkage coefficients were decoupled via multi-cycle coefficient of thermal expansion (CTE) tests and the calculated shrinkage coefficient showed excellent agreement with the direct dehydration measurements. Finally, a simplified equivalent calculation method was developed to map hygroscopic shrinkage to thermal expansion, and finite element simulations based on this approach demonstrated good consistency with experimental results. By incorporating moisture-induced deformation alongside thermal mismatch, this study provides critical insights for explaining FSAs deformation behavior.

Spatial structures exhibit complex load-transfer mechanisms, strong spatial coupling, and high sensitivity to environmental actions, which impose increasing demands on spatial structural health monitoring (SSHM). Advances in sensing technologies have enabled SSHM systems to acquire substantial data. Based on structural characteristics and monitoring requirements, this review defines multi-source data as complementary information differing in source, location, or temporal scale, and summarizes data foundations from field monitoring, numerical simulation, and experiments. Following the information flow from acquisition and quality assurance to condition estimation, deep learning (DL) methods are reviewed for compressive sensing, missing data recovery, response prediction, anomaly and damage detection. Analysis indicates that DL has potential for nonlinear feature extraction and spatiotemporal correlation modeling. However, existing studies remain dominated by specific applications and homogeneous data. Future directions involving heterogeneous data fusion, graph neural network (GNN), physics-informed neural network (PINN), and performance assessment are discussed. This review establishes a unified framework of SSHM, supporting the transition of DL from algorithmic validation toward practical applications.

Buildings integrated with ethylene-tetrafluoroethylene (ETFE) cushions as roofs and fa & ccedil;ades are increasingly adopted as lightweight and high-performance alternatives to glass curtain walls. However, limited understanding of their thermal behavior often leads to inaccuracies in building environmental design. Therefore, this study employs a methodology combining experiment, simulation and theory to evaluate the thermal performance of ETFE cushions. Hot-box tests were conducted on ETFE cushion models under varying temperature differences (10 degrees C, 20 degrees C, 30 degrees C, and 40 degrees C), installation angles (0 degrees, 45 degrees, and 90 degrees), and number of film layers (two and three). The results show that increasing the number of film layers from two to three nearly doubles the thermal resistance, whereas increasing the temperature difference from 10 to 40 degrees C reduces it by up to 22.1%, depending on the installation angle and layer. By contrast, the installation angle has a minor effect. Numerical simulations were subsequently carried out, which showed strong agreement with the experimental results. The simulations further elucidate the dominant heat transfer mechanisms: radiation contributed over 70% of the total heat flux and was mainly affected by temperature difference and number of layers, while inclination mainly affects convection by altering internal flow patterns. The thermal resistance calculation formula for rectangular ETFE cushions was finally proposed, which was corrected by the numerical results. The corrected formula, incorporating a perspective correction factor and a volume-equivalent thickness, proves strong applicability in calculating the thermal resistance of rectangular ETFE cushions. Generally, these findings provide valuable guidance for the environmental design of ETFE cushion buildings.

The integration of membrane structures with photovoltaic systems represents a promising low-carbon solution for green buildings and thin-walled structural applications. However, intrinsic material defects may cause tearing failures in architectural fabrics when exposed to the combination of external loads and high-temperature arising from solar radiation and photovoltaic components. To facilitate the practical application of building-integrated photovoltaic membranes, high-temperature uniaxial tearing tests were conducted on polyvinylidene fluoride (PVDF)-coated warp-knitted fabrics with pre-existing central notches. The influences of temperature, off-axis angle, slit parameters, and loading speed on tearing behavior were systematically examined. The results indicate that the tearing process comprises four characteristic stages: initial crack, crack opening, crack steady propagation, and crack unsteady propagation, accompanied by pronounced strain concentration at the notch tip. Increasing temperature significantly degrades material stiffness, with elastic stiffness decreasing by 72.1 % at 100 degrees C compared with 25 degrees C. The off-axis angle is the dominant factor governing tearing strength, reaching a maximum at 45 degrees and minima near 30 degrees and 60 degrees, approximately 30 % of the peak value. Slit parameters also markedly influence tearing resistance: increasing the slit orientation angle enhances tearing strength, whereas increasing slit length leads to a reduction. Loading speed has a relatively minor effect within the investigated range. Two-way analysis of variance reveals strong thermomechanical coupling between temperature and both off-axis angle and loading speed, while interactions involving crack-related parameters are comparatively weak. Generally, this study provides insight into the high-temperature tearing behavior of warp-knitted fabrics and contributes to the structural safety evaluation of photovoltaic membrane systems.

Flexible photovoltaic (PV) modules with thin frontsheet are increasingly demanded for lightweight and curved applications but remain susceptible to hail-induced damage under extreme weather conditions. This study presents a combined experimental and numerical approach to evaluate the hail impact response of lightweight flexible PV modules using a representative hail size derived from historical statistics. Based on microscopic characterization of the PV module, an enhanced numerical model that incorporates the elastic-plastic behavior and phase transition of hail is developed to reveal the stress propagation and transfer within the layered structure during impact. The model is validated against macroscopic impact experiments, which show localized cell damage with negligible electrical degradation. Stress analysis demonstrates that the thick encapsulant mitigates stress through the cushioning mechanism, whereas the stiff backsheet contributes to the global stress redistribution. The simulations capture a peak cell stress of approximately 116 MPa and estimate a corresponding fracture probability of 23.5% according to a statistical model. By quantitatively linking hail parameters, module design, and cell-level damage, this study can provide a comprehensive assessment for evaluating the impact resilience of advanced flexible PV modules from laboratory-scale testing to real-word deployment.