Effective Coefficient Of Thermal Expansion Research Articles

Numerical prediction of thermal conductivity and thermal expansion coefficient of glass fiber-reinforced polymer hybrid composites filled with hollow spheres

The optimal performance of composites enriched with hollow spheres has been reported in contemporary literature, whereas their thermal properties have received less attention. In this regard, a finite element method (FEM)-based micromechanical model has been developed systematically to investigate the role of intra-matrix embedding of hollow spheres on the thermal conductivity and coefficient of thermal expansion (CTE) of unidirectional fiber-reinforced hybrid composites. In so doing, the concept of representative volume element (RVE) considers microstructures comprising an epoxy matrix, E-glass fiber, and E-glass hollow spheres, assuming perfect bonding (ideal interface) between the components and modified approximate periodic boundary conditions. By computing the longitudinal and transverse temperature gradients generated due to the application of uniform heat flux as well as the geometrical variation in RVE owing to temperature enhancement, thermal conductivity and CTE have been respectively determined. Comprehensive evaluations have been conducted to examine the effects of microstructural-level features, including fiber volume content and orientation, plus volume content and thickness of hollow spheres, on the effective thermal conductivity and CTE of pseudo-porous ternary E-glass/epoxy composites.

Thermomechanical analysis of carbon fiber-reinforced polymer representative volume elements with voids

This work presents results of numerical simulations to investigate the effect of different void percentages on composite materials’ Coefficient of Thermal Expansion (CTE) and local stress fields. A random distribution of voids is considered within the Representative Volume Element (RVE) matrix, and different types of microstructures are considered, including square-packed and randomly distributed fibers. The use of a higher-order beam model within the framework of Carrera Unified Formulation (CUF) leads to a Component-Wise (CW) approach, resulting in an accurate, 3D description of the cross-section although using a 1D formulation. Numerical results for different fiber volume fractions and void concentration percentages demonstrate the agreement of the computed effective coefficients of thermal expansion of the present micromechanical thermoelastic model with references from the literature. The local stress fields are affected by voids, with higher effects over the matrix. Furthermore, higher void fractions lead to higher variability of stress peaks.

Multimaterial Additively Manufactured Metamaterials Functionalized with Customizable Thermal Expansion in Multiple Directions.

Metamaterials functionalized with customizable multidirectional coefficient of thermal expansion (CTE) are urgently needed for advanced shape control or dimensional stability under temperature variations. The currently reported metamaterials still lack the development of diverse base material systems and exploration of the multimaterial fabrication process. Especially, the reported range of customizable CTEs for metamaterials in multiple directions is limited within [-68.1, 56.4] ppm/°C. Here, this work explicitly proposes a strategy for closely linking base materials, additive manufacturing (AM) process, architecture, and CTE tunability, in order to provide a general guideline for the design or customization of such metamaterials. In detail, first, we systematically identify the key process parameters and related performance for additive manufacturing of polymers and propose various multimaterial systems such as polypropylene-polycarbonate (PP-PC). Then, six types of metamaterials have been fabricated with high quality by the established multimaterial additive manufacturing. By measuring the effective CTEs in multiple directions, the CTE tunability of metamaterials, including large positive values (+523.36 ppm/°C) and large negative values (-230.61 ppm/°C), far beyond the literature-reported CTE range, has been experimentally verified. Further, we have developed a bidirectional requirement-solution strategy here that acts as a bridge between design and fabrication. This work opens advanced avenues for metamaterials with multidirectionally customizable and extensive CTE tunability for a variety of engineering applications such as actuators, thermal stress relief, and improved structural stability.

Negative thermal expansion mechanical metamaterial using the swastika shape

Materials and structures operating under thermal fluctuation encounter thermal expansion and/or thermal stresses, which require components that allow expansion compensation in certain directions and zero expansion in other directions. A 2D mechanical metamaterial with negative thermal expansion and zero thermal expansion in the in-plane and out-of-plane directions, respectively, is established herein by inspiration from the swastika shape. The swastika units are rigid and are interconnected to each other by positioning the connecting materials, which possess high thermal expansion, at the inner surfaces of the swastika arms. In this way, thermal expansion of the connecting materials tends to draw the swastika units towards each other, thereby generating an overall thermal contraction. Theoretical results indicate that the negativity of the thermal expansion is enhanced by the size of the connecting materials, but suppressed by the size of the swastika units. The results also reveal that the connecting material thickness and the swastika arm length exert major roles while the connecting material length and the swastika arm width play minor roles in influencing the effective thermal expansion coefficient of the metamaterial. These observations offer solutions for quick coarse-tuning and slow fine-tuning of the metamaterial’s CTE. Although swastikas have cultural, religious, and even political connotations, the author would like to clarify that the swastika considered herein has been used purely for its geometric shape. The author does not intend to convey any cultural or ideological meaning by its use in this article.

Expansivity of Fused Quartz Glass Measured with 6 x 10-10/K

Thermal expansion sometimes dominates uncertainty in a precision measurement. A cell-based refractometer has been designed at NIST which targets 10−6 relative uncertainty in the measurement of helium refractivity; in terms of absolute refractive index at ambient conditions, the accuracy goal is 3 × 10−11. To achieve this level of accuracy, the length of a 0.5 m gas cell would need to be known within 100 nm. This is achievable when cell length is measured by coordinate-measuring machine at 20 °C. However, the refractometer will operate at the thermodynamically known fixed-points of water and gallium, near 0 °C and 30 °C, respectively. The cell is made from fused quartz glass, which has a nominal thermal expansion coefficient of 0.4 (μm/m)/K. Therefore, to scale the accuracy of the dimensional metrology across 20 °C to the triple-point of water requires that the thermal expansion coefficient of fused quartz glass is known within 10 (nm/m)/K, or 2.5 %. A method is described to measure the thermal expansion coefficient of fused quartz glass. The measurement principle is to monitor the change in resonance frequency of a Fabry–Perot cavity as its temperature changes; the Fabry–Perot cavity is made from fused quartz glass. The standard uncertainty in the measurement was less than 0.6 (nm/m)/K, or 0.15 %. The limit on performance is arguably uncertainty in the reflection phase-shift temperature dependence, because neither thermooptic nor thermal expansion coefficients of thinfilm coatings are reliably known. However, several other uncertainty contributors are at the same level of magnitude, and so any improvement in performance would entail significant effort. Furthermore, measurements of three different samples revealed that material inhomogeneity leads to differences in the effective thermal expansion coefficient of fused quartz; inhomogeneity in thermal expansion among samples is 24 times larger than the measurement uncertainty in a single sample.

Measurement of Thermal Stress by X-ray Nano-Diffraction in (111)-Oriented Nanotwinned Cu Bumps for Cu/SiO2 Hybrid Joints.

X-ray nanodiffraction was used to measure the thermal stress of 10 µm nanotwinned Cu bumps in Cu/SiO2 hybrid structures at -55 °C, 27 °C, 100 °C, 150 °C, and 200 °C. Bonding can be achieved without externally applied compression. The X-ray beam size is about 100 nm in diameter. The Cu bump is dominated by (111) oriented nano-twins. Before the hybrid bonding, the thermal stress in Cu bumps is compressive and remains compressive after bonding. The average stress in the bonded Cu joint at 200 °C is as large as -169.1 MPa. In addition, using the strain data measured at various temperatures, one can calculate the effective thermal expansion coefficient (CTE) for the 10 µm Cu bumps confined by the SiO2 dielectrics. This study reports a useful approach on measuring the strain and stress in oriented metal bumps confined by SiO2 dielectrics. The results also provide a deeper understanding on the mechanism of hybrid bonding without externally applied compression.

Novel metamaterial structures with negative thermal expansion and tunable mechanical properties

The thermal expansion and stiffness characteristics are significant in determining the responses of lightweight mechanical metamaterials in a thermal environment. This paper proposed a novel trapezoid unit with negative thermal expansion (NTE) by three conventional materials with positive thermal expansion, and constructed a series of lightweight metamaterials by sharing edges and sharing vertexes. The effective linear coefficients of thermal expansion (CTE) of these metamaterial structures are theoretically explored by considering axial and bending deformations. Based on Euler beam theory, the effective linear elastic stiffnesses of these metamaterials are given accurately by the stiffness matrix method. The accuracy of the theoretical effective CTE and stiffness is well verified by numerical modeling. The effective linear CTE, elastic stiffness, and Poisson's ratio of these metamaterials can be programmable by controlling geometrical parameters and material properties. The NTE effect can be achieved in ET, EQ, EH, and VT metamaterials due to the presence of re-entrant structures, in which the ET metamaterial can fulfill the maximum magnitude NTE. The NTE and negative Poisson's ratio can simultaneously be realized in EQ metamaterial. Significantly, a broader range of CTE from negative to positive values can be fulfilled in these metamaterials compared with the conventional triangle unit. Furthermore, the high specific stiffness with extremely low thermal stress can be obtained in EQ, VT, and VH metamaterials, which benefits the stability controlling and enhancing natural frequencies of structures in a thermal environment.

Three-dimensional bi-metallic lattice with multi-directional zero thermal expansion

Metamaterials with zero coefficient of thermal expansion (CTE) are of increasing interest with the rapid development in aerospace applications. Despite numerous two-dimensional (2D) metamaterials with high thermal stability have been investigated, studies on three-dimensional (3D) zero CTE structures are still limited by the complexity of fabrication and geometric connections. In this study, novel 3D bi-metallic lattices with multi-directional zero CTEs are designed, fabricated and experimentally validated. A theoretical method has been developed to predict the effective CTE of the lattice with different materials and geometric parameters and illustrated by comparison with experimental results and numerical simulation results. The 3D lattice had identical effective CTEs along three orthogonal directions and the CTE results were extreme close to zero (0.62 ppm/°C), which is the first time to achieve nearly zero CTE over a wide temperature range in 3D metallic lattice. In addition, the mechanical performance and the effect of geometric parameters of the lattice has been investigated using finite element analysis (FEA). Different thermal deformation mechanisms in the lattice are revealed by different selections of materials for connection bar. The proposed design method and thermal mechanisms are promising for the design of the bearing platform with zero CTE in aerospace engineering.

Tailorable thermoelasticity of cubic lattice-based cellular and granular materials by prestress

When a cubic lattice packaged by a boundary layer is subjected to a mechanical and temperature load, the force and length change of the bonds are equivalently evaluated by the average stress and strain of the unit cell. Provided a displacement gradient variation at a certain stress state, the variation of stress related to the strain variation provides the effective stiffness of the material at the corresponding configuration. It is discovered that the effective elasticity and thermal expansion coefficient can be tailored by the prestress through the boundary layer, which generates a configurational stress. Because the bonds of a cubic lattice depend on the material types, we consider the harmonic potential of springs for cellular lattices and Hertz's contact potential of balls for granular lattices, respectively. The cubic symmetry of effective elasticity is demonstrated for the three types of cubic lattices. By taking the orientational average, isotropic elastic constants can be obtained for randomly oriented lattices. As the bond length changes with the prestress of the boundary layer and controls the thermoelastic behavior, a novel design method of lattice-based materials confined in a spherical shell is demonstrated to achieve zero thermal expansion and a positive temperature derivative of elasticity.

4D printed thermally tunable metasurface with continuous carbon fibre

ABSTRACT Multifunctional metamaterials with unique electromagnetic and mechanical properties are highly desired in many fields, including space exploration and satellite communication, where broad tunability of the working frequency and controllable mechanical deformation properties are usually necessary. In this study, we propose a metasurface exhibiting simultaneous electromagnetic frequency selection capability and isotropic negative/positive/near-zero thermal expansion. The metasurface is designed based on chiral structures and is fabricated via 4D printing of continuous fibre composites. Both the effective thermal expansion coefficient and electromagnetic transmission band were investigated in different structural parameters based on theoretical calculation, finite element analysis simulations and experiments. The measured results were in good agreement with the theoretical data which reveal the influence law of structural parameters on thermal deformation and electromagnetic frequency control. Thus, the electromagnetic functionality of the metasurface can be thermally controlled and is expected to be useful in extreme situations where the coupling of multiphysical fields is required.

Development of a hybrid model for fuel performance analysis of spherical fuel elements under normal conditions

The spherical fuel element (SFE) dispersed with many tri-isotropic fuel (TRISO) particles has been primarily employed in the high-temperature gas-cooled reactor. Owing to the complex structure of SFE, behaviors will be evolved for both TRISO particles and the fuel matrix with the increasing burnup. To evaluate the fuel performance of SFE, the homogenization method has been conventionally adopted for SFE scale modeling, and dispersed TRISO particles are analyzed subsequently with fixed temperature boundary conditions. However, owing to the varying properties of TRISO particles under reactor operation, the homogenization models dedicated to certain circumstances can hardly reflect the properties evolution of TRISO with high fidelity, which may lead to uncertainties in analysis results. To this end, a hybrid model, namely the conventional homogenization model informed by the lower scale model online, has been developed in this paper, which may increase modeling fidelity for both SFE and particles. Specifically, property models for the TRISO particle and graphite matrix have been implemented in COMSOL. Subsequently, based on the linking of COMSOL and MATLAB, the hybrid model for SFE analysis was established. Through the hybrid model, the temperature field and stress distribution of TRISO, the evolution of effective properties, and the thermal and mechanical state of the SFE were obtained and analyzed. The results show that within the scope of this paper, the central temperature of TRISO in the innermost region rises with the increasing burnup for the decreasing thermal conductivity of materials, and the peak value is about 1324 K, which is about 60 K higher than that in the outermost region. The difference in the maximum plenum pressure is more than 5 MPa among TRISO particles, which is mainly caused by the variations in CO production. Consequently, the hoop stress of SiC in the outermost region is slightly elevated. The distribution of effective thermal conductivity (ETC) for TRISO is nearly 4.3 W/(m·K) at the beginning of life (BOL), while it was reduced to 3.6 W/(m·K) at the end of life (EOL). There are marginal variations along the radial direction for the ETC of TRISO. Meanwhile, the ETC of SFE decreases from about 21 W/(m·K) for fresh fuel to 13 W/(m·K) for spent fuel. The predicted effective elastic modulus and coefficient of thermal expansion of SFE increase gradually versus time. The former is caused by the densification of pyrolytic carbon, and the latter is mainly determined by the high volume fraction of matrix and the changes of CTE for pyrolytic carbon. In addition, the comparison in the temperature field between the proposed model and the Differential Effective Material Theory (D-EMT) model may further demonstrate the feasibility and effectiveness of the hybrid model.

Metamaterial with Tunable Positive and Negative Hygrothermal Expansion Inspired by a Four-Fold Symmetrical Islamic Motif

A metamaterial with controllable positive and negative thermal and hygroscopic expansions is investigated herein by inspiration from a range of Islamic geometric patterns. Constructing from eight pairs of pin-jointed Y-elements, each unit cell manifests eight rhombi that are arranged circumferentially, thereby manifesting four axes of symmetry. By attachment of bimaterial spiral springs of contrasting expansion coefficients to the far arms of the paired Y-elements, a change in the environment’s thermal or hygroscopic condition alters the offset angle of the paired Y-elements such that the unit cell of the metamaterial ranges from the eight-pointed star to the regular octagon. The effective coefficient of thermal expansion (CTE) and the coefficient of moisture expansion (CME) of this metamaterial were developed for small and large changes in environmental fluctuations using infinitesimal and finite models, respectively. Generated data indicates that the sign and magnitude of the effective thermal and hygroscopic expansion coefficients can be controlled by geometrical descriptors of the bimaterial spiral spring—such as its coil number and the ratio of its mean radius to its thickness—as well as the properties of the bimaterial’s layers such as their expansion coefficients, Young’s moduli and, in the case of effective hygroscopic expansion, their relative absorptivity. The obtained results suggest that the proposed metamaterial can be designed to perform as highly sensitive thermal and/or moisture sensors, as well as other functional materials or devices that take advantage of environmental changes as stimuli.

Lightweight 3D carbon fibre reinforced composite lattice structures of high thermal-dimensional stability

In this study we develop and investigate a novel lightweight 3D composite lattice structure of high thermal-dimension stability, i.e., with zero coefficient of thermal expansion (CTE). First, a base planar composite lattice, comprised of a continuous carbon fibre reinforced polyamide (CCF/PA) central cross-lattice and four short carbon fibre reinforced polyamide (SCF/PA) outer strips for good thermal-dimensional stability, was additively manufactured in a rotated cross-ply sequence, i.e., at alternative 45°/135°. Experiments were performed to validate an effective numerical model where effective thermo-elastic properties were applied; the results proved the effective numerical model’s accuracy and efficiency. Second, a novel 3D composite lattice structure was developed and calculated, exhibiting a negative effective CTE at −0.18×10 −6 /℃, based on the planar composite lattices. Then, parametric analysis was performed to investigate the effects of geometric parameters on the effective CTE and density. Finally, lightweight optimisation was conducted with a constraint of effective CTE as zero. The results show that the optimal 3D composite lattice structure can achieve an effective density of 0.0266 g/cm 3 and an effective CTE of 0.0173×10 −6 /℃, which are 15.3% and 90.39%, respectively, improved over the initial 3D composite lattice. The outcomes proved the effectiveness of the design in achieving a novel lightweight 3D composite lattice structure of high thermal-dimensional stability.

Physical Mechanism and Chemical Trends in the Thermal Expansion of Inorganic Halide Perovskites.

The considerable thermal expansion of halide perovskites is one of the challenges to device stability, yet the physical origin and modulation strategy remain unclear. Herein, we report first-principles calculations of the thermal properties of halide perovskites at 300 K using oxides as a reference. We found that the large thermal expansion of halide perovskites can mainly be attributed to their low bulk modulus and volumetric heat capacity because of the soft crystal lattice, whereas composition-dependent anharmonicity emerges as the most important factor in determining thermal expansion with the same structure. We discovered that thermal expansion of halide perovskites can be decreased by weakening the B-X bond to promote the octahedral anharmonicity. We further proposed an effective thermal expansion coefficient descriptor of halide perovskites with a Pearson correlation coefficient of nearly -80%. Our findings provide insights into the underlying mechanisms and chemical trends in the thermal expansion behavior of halide perovskites.

Thermal expansion and bandgap properties of bi-material triangle re-entrant honeycomb with adjustable Poisson's ratio

The future mechanical metamaterials should achieve multifunctional integration to meet the requirements of structures and materials in the aviation field for service in complex environments. In this paper, a bi-material triangle re-entrant honeycomb (BTRH) with the tunable coefficient of thermal expansion (CTE), Poisson's ratio (PR), and bandgap is proposed. Analytical analysis and numerical simulations are implemented to quantify the evolution of the effective CTE, PR, and Young's modulus. Experiments are conducted to verify the correctness of the theory of the effective PR and Young's modulus. Based on Bloch's theorem, the band structures of the BTRH are calculated by finite element analysis, and the correctness of the band structure calculation is verified by calculating the transmission characteristic curve. The effects of geometric parameters and material combinations on the mechanical properties are investigated systematically. The results of analytical and numerical simulations exhibit that the CTE and PR can be coupled with regulation from positive to negative through changing the geometry configuration and material combinations of the BTRH. Meanwhile, the function of tunable bandgap and large total effective bandgap width can be obtained. This work provides an important reference for the rational design of multifunctional metamaterials to maintain shape stability and efficient sound insulation.

Tunable thermal expansion and bandgap properties of the bi-material-directional honeycomb metamaterial

The excellent shape stability of thermally expanded metamaterials and the good bandgap properties of acoustic metamaterials have a wide range of promising applications in aerospace and sensors. Here, a bi-material-directional honeycomb metamaterial (BHM) with tunable coefficient of thermal expansion (CTE) and bandgap properties is proposed. The theoretical analysis and numerical simulations are employed to reveal the thermal deformation mechanism of the BHM. In addition, the analytical expression of the effective Young’s modulus is established by considering both tensile and bending deformation. Based on the Bloch theorem, the band structures of the BHM are calculated by the finite element method. Parameter analysis confirms that the CTE and bandgap of the BHM can be simultaneously regulated and drastically adjusted by changing the geometric parameters and material combinations. Meanwhile, the coupling relationship of the effective CTE, Young’s modulus, and total effective bandgap width are investigated. The results show that the BHM can have tunable CTE function and large total effective bandgap width by selecting suitable parameters while satisfying stiffness requirements. This study achieves a dual objective of specific CTE properties and bandgap design through rational material selection and shape design, which makes the metamaterials have better tunability and multifunctionality.

Stiffness characteristics for bi-directional tunable thermal expansion metamaterial based on bi-material triangular unit

The stiffness and coefficient of thermal expansion (CTE) are of great significance for lightweight metamaterials that adapt to variations in temperature. Toward this goal, bi-directional tunable thermal expansion metamaterial based on bi-material triangular unit is reported and fabricated using multi-layer assembly strategy. The CTE and stiffness of the designed metamaterial can be programmed in two directions, which provides a method for existing metamaterials can only be regulated in a single direction. To describe the mechanical properties, theories of the effective CTE and stiffness are established considering bending, tensile, and shear deformations and verified by numerical analysis. The mechanical response, especially stiffness, of the multi-material metamaterial is experimentally verified. By rationally modulating the cell architectures, the high relative stiffness and tunable CTE can be realized. In particular, the proposed metamaterial achieves a wide range of tunable CTEs from -31.16 ppm/°C to 56.43 ppm/°C. The exclusive integrated functions of the metamaterials including low density, considerable stiffness, and tunable CTE are superior compared with common materials. The coupling design of the CTE, stiffness, and relative density further demonstrates that this work has a positive effect on the development of metamaterials in aerospace applications and other fields.

Numerical Study of Simultaneously Negative Thermal Expansion and Poisson's Ratio in a Class of Auxetic Structures

Cellular solids whose ligaments are made of two distinct materials are constructed for studying their auxeticity and negative thermal expansion via 2D models with the methodology of finite‐element numerical analysis. Three bimaterial cellular models with various radii of ligament curvature (Rc = 5, 8, 11 cm) are analyzed. It is found that when the ligaments comprise aluminum and titanium alloy with Rc = 5 cm, the cellular solid exhibits simultaneous negative effective Poisson's ratio (−0.418) and negative thermal expansion coefficient (−20.82 × 10−6 K−1). When the radius of ligament curvature increases, auxeticity is less pronounced. Positive and negative thermal expansion can be tuned solely by the coefficients of thermal expansion of ligaments’ constituents. Furthermore, smaller radii of curvature give rise to larger negative thermal expansion. In addition, modulus mismatch in the bimaterial ligament can be used to tune overall properties. Our findings herein may serve as foundations for the future quantitative design of such cellular materials. In addition, effective Poisson's ratio and coefficient of thermal expansion can be positively or negatively enhanced due to the interplay between the positive and negative phases. Interactions between negative stiffness and larger curvatures may make the system less unstable.

A comparative analysis of thermos-mechanical behavior of CNT-reinforced composite plates: Capturing the effects of thermal shrinkage

In this study, an analytical model based on the classical laminate theory (CLT) is developed for the prediction of the effective thermal expansion coefficients (ETECs) of general angle-ply laminates (symmetrical and asymmetrical). The applications of the derived model are shown by solved examples for the prediction of ETEC of carbon nanotube-reinforced (CNTRC) angle ply laminates for various ply angles. CNTRC laminates with a negative thermal coefficient (NTC) are obtained and considered as a special case. For an extreme case, a laying angle of (35/-35)3T and (55/-55)3T, along with an NTC of −0.79 × 10−5/K is achieved. Meanwhile, the Reddy shear plate model is extended to the framework of Von Kármán nonlinearity. The corresponding dynamic equations are analytically established. With the help of the two-perturbation approach, the deflection time history curves of the forced vibration are obtained. Numerical results show that the thermal-vibration behaviors may be adjusted and controlled by changing the TEC and functionally graded pattern. The presented analytical results not only are theoretically fundamental for understanding the thermal-vibration behavior of FG-CNTRC but also serve as guidelines for NTC design of composited laminated structures.

Smart sandwich structures with dynamically switchable in-plane thermal expansion coefficients from positive to negative

Capacity to autonomously respond to external stimuli with some switchable structural shapes/properties/functions is highly desirable in many occasions where either system service environments or functional requirements are dynamically changing over time. In this paper, we conceptually propose a new type of smart sandwich structure with the ability to dynamically switch in-plane coefficients of thermal expansion (CTEs) from initially positive to negative or even zero value through internal microstructural transformation triggered solely by a certain temperature stimulus. To this end, a thermally driven snap-through action is purposely added into the design of the microstructure of periodic face-sheets by introducing an active spherical shell component constituted by two materials with different positive CTEs. The lattice core is connected to the upper and lower face-sheets for preventing the overall transverse deformation of face-sheet during temperature variation. Numerical simulations are subsequently carried out to demonstrate the completely reversible snap-through behavior, and the designed function of dynamically switchable in-plane CTE is also validated. Numerical results also reveal that the increasing thickness ratio of high CTE layer to low ones causes a decreased tendency for effective in-plane CTE before snapping, but the influence on after-snapping CTE is negligible. Similarly, the larger shell span brings an obvious increase in effective after-snapping in-plane CTE but without influence on before-snapping CTE. These significant results are beneficial to be summarized as practical design skills for simultaneously designing customized snap-through temperature and effective before or after-snapping in-plane CTE, all of which enable the proposed smart sandwich structure to be flexible to satisfy various requirements in more potential applications.