In-plane Mechanical Properties Research Articles

In-plane energy absorption characteristics and mechanical properties of 3D printed novel hybrid cellular structures

This paper developed and fabricated four novel hybrid metamaterial structures by combining honeycomb, re-entrant, and star-shaped unit-cells by additive manufacturing (AM) techniques and tested them to evaluate the enhanced mechanical properties. Then, the in-plane energy absorption capacity and uniaxial compressive response of novel structures were compared using finite element simulation and experimental techniques. In addition, all structures' failure modes and deformation mechanisms were explained in detail. A type one re-entrant-star-shaped (RS1) structure demonstrated higher compressive strength, plateau stress, and energy absorption than other structures, mainly due to the unique deformation mechanism. For comparing energy absorption and mechanical properties between the parent and hybrid cellular structures (HCS), the RS1 performed the best. A Poisson's ratio curve for HCS was also obtained, and the relevant results were analyzed. In addition, the results of this research should aid in determining the best unit-cell arrangement for HCS to improve their mechanical properties and energy absorption.

In-plane dynamic crashing behavior and energy absorption of novel bionic honeycomb structures

A series of novel bionic honeycombs (bio-honeycombs) are proposed by incorporating the microstructure of the beetle elytra intersection unit into the regular hexagonal honeycomb (Hex) cell. To explore the in-plane mechanical properties and energy absorption performance of bio-honeycombs under different impact speeds, finite element (FE) models are established and verified by empirical formulas and current experiments. The results indicate that the bio-honeycombs outperform the Hex in terms of energy absorption capacity, and the nominal stress–strain curves of the bio-honeycombs show two prominent stages (stage Ⅰ and stage Ⅱ) under quasi-static and mid-impact. Bionic units also undergo two evident deformation stages: preliminary collapse and further crushing. The bending and traction of bionic units make more adjacent cells added to the collapse earlier, forming a global crushed trend, leading to an interesting phenomenon that the localized band of bio-honeycombs are always wider than that of Hex. Also, negative Poisson’s ratio is observed in stage Ⅱ from several bio-honeycombs under quasi-static and mid-speed due to bionic units' bending and traction in the further crushing stage. Besides, the number and distribution of ribs have a considerable impact on the crashworthiness of bio-honeycombs. Compared with the Hex, the incorporated bionic units reduce the peak crushing force (PCF) while improving the crashworthiness of bio-honeycomb in the case of the same relative density, which provides a promising potential solution to strengthen the energy absorption performance of honeycomb structures.

Designing a Cruciform Specimen via Topology and Shape Optimisations under Equal Biaxial Tension Using Elastic Simulations.

Stress uniformity within the gauge zone of a cruciform specimen significantly affects materials’ in-plane biaxial mechanical properties in material testing. The stress uniformity depends on the load transmission of the cruciform specimen from the fixtures to the gauge zone. Previous studies failed to alter the nature of the load transmission of the geometric features using parametric optimisations. To improve stress uniformity in the gauge zone, we optimised the cross-arms to design a centre-reduced cruciform specimen with topology and shape optimisations. The simulations show that the optimised specimen obtains significantly less stress variation and range in the gauge zone than the optimised specimen under different observed areas, directions, and load ratios of von Mises, S11, S22, and S12. In the quantified gauge zone, a more uniform stress distribution could be generated by optimizing specimen geometry, whose value should be estimated indirectly each time through simulations. We found that topology and shape optimisations could markedly improve stress uniformity in the gauge zone, and stress concentration at the cross-arms intersection. We first optimised the cruciform specimen structure by combining topology and shape optimisations, which provided a cost-effective way to improve stress uniformity in the gauge zone and reduce stress concentration at the cross-arms intersection, helping obtain reliable data to perform large strains in the in-plane biaxial tensile test.

In-plane elasticity of a novel arcwall-based double-arrowed auxetic honeycomb design: Energy-based theoretical analysis and simulation

In this paper, a new design of auxetic honeycomb is proposed for mechanical performance enhancement by combining the arc-shaped wall and the normal double-arrowed auxetic configuration. On basis of Mohr's 2nd theorem and Castigliano 2nd theorem, an analytical model considering strut bending and stretching is developed to modulate the in-plane mechanical properties of the proposed honeycomb with the geometric parameters. Further, an integrated experimental, simulation and theoretical approach is carried out to investigate its elastic properties and Poisson's ratios in a wide range. The comparison shows that the theoretical results are in good agreement with the experimental and simulation results, verifying the established analytical model. The results reveal that both the in-plane modulus and the Poisson's ratio of the proposed auxetic honeycomb are simultaneously improved compared to the typical double-arrowed and the re-entrant hexagonal designs, and show high and diverse dependencies on the geometric parameters. Additionally, the honeycomb features a stiffer modulus and stronger auxeticity along y direction than that along x direction when the arc angle of “bone”, θ1, not exceeding a “turning point”. The present design may provide an extensive reference for the design and application of mechanical meta-materials.

In-plane mechanical properties of a novel hybrid auxetic structure

This paper presents a novel hybrid auxetic structure with enhanced mechanical properties, combining the re-entrant and double-arrowhead structures, based on the structural stretching-dominated deformation mechanism. The unit cell of the developed hybrid structure comprises an external quadrilateral frame and an internal arrowhead part. The theoretical analysis model for predicting its in-plane mechanical properties in the two principal directions is presented and verified by both numerical simulations and experimental measurements. On this basis, a parametric study on the in-plane mechanical properties of the hybrid structure is performed to optimize geometrical parameters. The results show that both the negative Poisson’s ratio behavior and the elastic properties of the hybrid structure can be enhanced by increasing the length of the vertical wall or reducing the angle of the inclined wall in the internal arrowhead part. The hybrid structure, with the obvious difference in elastic properties between the two principle directions, can be obtained by individually adjusting the width of the hybrid unit cell, while the elastic properties in bothdirections can be improved by simultaneously reducing the length of the vertical wall and the width of the hybrid unit cell. In addition, compared with the re-entrant and double-arrowhead structures, the hybrid structure demonstrates higher elastic moduli and a wider range of Poisson’s ratios from negative to positive. The study provides guidance for the optimized design of hybrid auxetic structures in practical applications.

A novel enhanced anti-tetra-missing rib auxetic structure with tailorable in-plane mechanical properties

In analogy with the enhanced hexa-missing rib structure, a novel enhanced anti- tetra-missing rib structure was proposed in this work. Using a simple energy-based approach, mechanical modelling under infinitesimal deformation was proposed to provide guidelines for determining the geometries with targeted mechanical properties. It is shown that the proposed structure provides tunable Poisson’s ratios and elastic and shear moduli in wide ranges. The analytic solutions of the effective Poisson’s ratio, elastic and shear moduli from the mechanics model were validated by systematic finite element (FE) calculations on one unit-cell with considering periodic boundary conditions (PBCs). The underlying deformation mechanism accounting for the auxetic behavior on different geometric parameters of the proposed design was then investigated by elaborated FE analysis in a large deformation regime. The targeted NPR performance was also verified with a nonlinear base material. Uniaxial tensile experiments and the corresponding numerical simulations for lattice structures consisting of an array of proposed unit-cells were also performed to validate the theoretical and FE results obtained from one unit-cell analysis.

In-plane mechanical properties of birch plywood

There is an increasing demand for engineered wood products in modern structures. Birch plywood is promising in structural applications, due to the combined advantages of its superior mechanical properties and the cross lamination configuration. However, the off-axis mechanical properties of birch plywood have not been thoroughly investigated. The aim of this paper is to establish a comprehensive experimental dataset that could serve as the input in the analytical or numerical models to design birch plywood under various load conditions. Specifically, tensile, compressive and shear tests were conducted under five different angles to the face grain, i.e., from 0° (parallel) to 90° (perpendicular) to the face grain, with an interval of 22.5°. The stress–strain relationships, failure modes, strength and elastic properties of birch plywood are highly dependent on the load-to-face-grain angle. The strength and the elastic properties are also predicted by various analytical and empirical models. Parametric analyses are performed to study the influence of the interaction coefficient F12 in Tsai-Wu failure criterion and the Poisson’s ratio νxy in the transformation model on the predicted strength and modulus respectively. Lastly, the possibilities of predicting the on-axis shear modulus based on the off-axis uniaxial tests are discussed in this paper.

Plant-inspired multi-stimuli and multi-temporal morphing composites

Plants are inspiring models for adaptive, morphing systems. In addition to their shape complexity, they can respond to multiple stimuli and exhibit both fast and slow motion. We attempt to recreate these capabilities in synthetic structures, proposing a fabrication and design scheme for multi-stimuli and multi-temporal responsive plant-inspired composites. We leverage a hierarchical, spatially tailored microstructural and compositional scheme to enable both fast morphing through bistability and slow morphing through diffusion processes. The composites consisted of a hydrogel layer made of gelatine and an architected particle-reinforced epoxy bilayer. Using magnetic fields to achieve spatially distributed orientations of magnetically responsive platelets in each epoxy layer, complex bilayer architectural patterns in various geometries were realised. This feature enabled the study of plant-inspired complex designs, via finite element analysis and experiments. We present the design and fabrication strategy utilizing the material properties of the composites. The deformations and temporal responses of the resulting composites are analysed using digital image correlation. Finally, we model and experimentally demonstrate plant-inspired composite shells whose stable shapes closely mimic those of the Venus flytrap, while maintaining the multi-stimuli and multi-temporal responses of the materials. The key to achieving this is to tune the local in-plane orientations of the reinforcing particles in the bilayer shapes, to induce distributed in-plane mechanical properties and shrinkage. How these particles should be distributed is determined using finite element modelling. The work presented in this study can be applied to autonomous applications such as robotic systems.

Comparative study of the mechanical properties of woven and unidirectional fibres in discontinuous long-fibre composites.

Discontinuous long-fibre (DLF) composites can be made with randomly oriented unidirectional pre-impregnated composite chips. High fibre volume fraction unidirectional fibre chips provide good mechanical properties to the DLF composite architecture, which enables this material to contribute to bridging the gap between continuous-fibre and randomly-oriented short-fibre composites. However, it is well known that unidirectional fibres have highly anisotropic in-plane behaviour, which causes weak points in the parts when chips are oriented at unfavourable angles. This can be problematic since chips are randomly oriented in DLF composites. To overcome this problem, this research utilizes woven fibre chips instead of unidirectional fibre chips to fabricate DLF composites. Woven fibres diminish the potential for weak points due to their more homogenized in-plane mechanical properties. For comparison purposes, compression moulded carbon/PEI samples were made from both unidirectional chips and 5HS woven chips. Bending and tensile tests following ASTM guidelines were performed to compare both types of fibre arrangement. The results show that woven fibre chips increase the mechanical properties of the DLF composites and reduce their variability.

The effects of compaction and interleaving on through-thickness electrical resistance and in-plane mechanical properties for CFRP laminates

The electrical conductivity of carbon fibre reinforced polymer (CFRP) laminates has previously been shown to be significantly improved by using different electrically functionalized interleaves - Functional Interleave Technology (FIT), particularly in through-thickness direction. Here, the mechanism of FIT is explored via the influence of compaction and interleaving of nickel plated polyester non-woven veils (NPVs) on through-thickness electrical conductivity and in-plane mechanical properties for the CFRP laminates are investigated. The through-thickness electrical property is found to be dominated by the electrically conductive network elements (carbon fibres) and components (carbon fibre layers and NPV layers), which, in turn, is strongly affected by compaction. By using the highly conductive NPVs, the through-thickness resistivity for cured FIT laminates was consistently lowered from 9.3 Ω⋅m to 0.48 Ω m and 1.54 Ω⋅m to 0.016 Ω m for 56% and 64% carbon fibre volume fraction laminates, respectively. The conductive mechanism of FIT specimens follows the series-resistor model, providing the potential to predict the through-thickness electrical conductivity (TTEC) value by interleaving the desired number of NPV layers. Investigation of in-plane mechanical properties indicates the flexural properties and interlaminar shear strength (ILSS) are less affected by compaction. Meanwhile, a 20% reduction of ILSS for FIT laminates is detected because of the lower intra-ply shear resistance of NPV layers.

Toughening and Healing of CFRPs by Diels-Alder-Based Nano-Modified Resin through Melt Electro-Writing Process Technique.

In the current study, a novel approach in terms of the incorporation of self-healing agent (SHA) into unidirectional (UD) carbon fiber reinforced plastics (CFRPs) has been demonstrated. More precisely, Diels–Alder (DA) mechanism-based resin (Bis-maleimide type) containing or not four layered graphene nanoplatelets (GNPs) at the amount of 1 wt% was integrated locally in the mid-thickness area of CFRPs by melt electro-writing process (MEP). Based on that, CFRPs containing or not SHA were fabricated and further tested under Mode I interlaminar fracture toughness experiments. According to experimental results, modified CFRPs exhibited a considerable enhancement in the interlaminar fracture toughness properties (peak load (Pmax) and fracture toughness energy I (GIC) values). After Mode I interlaminar fracture toughness testing, the damaged samples followed the healing process and then were tested again under identical experimental conditions. The repeating of the tests revealed moderate healing efficiency (H.E.) since part of the interlaminar fracture toughness properties were restored. Furthermore, three-point bending (3PB) experiments were conducted, with the aim of assessing the effect of the incorporated SHA on the in-plane mechanical properties of the final CFRPs. Finally, optical microscopy (OM) examinations were performed to investigate the activated/involved damage mechanisms.

Spanwise wing morphing using multistable cellular metastructures

Morphing wings have the potential to provide additional functionality or increased performance to aircraft that serve in multiple roles and exhibit distinct aerodynamic characteristics. In-flight aspect ratio adaptation from spanwise morphing is one avenue for achieving this potential. This shape adaptability would allow the aircraft to extend the wings for an efficient loitering mode and retract them to better enable a high-speed dash. Spanwise morphing has historically been accomplished through the use of telescoping mechanisms, which lead to greater mechanical complexity and increased weight. This paper proposes a novel, lightweight, compliant structure composed of cellular metamaterials exhibiting multiple stable shapes. These metastructures enable spanwise morphing by allowing large, elastic deformations while maintaining their ability to bear loads. The physical and mechanical properties of a selection of multistable honeycombs with different unit cells are characterized using analytical and numerical methods. Their in-plane and flexural mechanical properties and their structural efficiency are compared to each other and to a conventional hexagonal honeycomb. Two multistable honeycombs are selected and utilized to develop a beam-like metastructure capable of shape adaptation in a single direction. The flexural mechanical properties of this metabeam are investigated using numerical and physical methods. We demonstrate the viability of the metabeam as a shape adaptable metastructure by developing a hybrid span-morphing wing concept that combines conventional, rigid structures with the compliant metabeam. The wing is analyzed using an uncoupled static aeroelastic tool to assess its performance under aerodynamic loading, showing the ability to increase lift from spanwise morphing without increasing wing flexural deflection.

2D Janus and non-Janus diamanes with an in-plane negative Poisson's ratio for energy applications

Motivated by the successful synthesis of 2D C2F diamanes [Bakharev, P.V. et al., Nat. Nanotechnol. 15, 59–66 (2020)], we have systematically investigated the structural stability, in-plane mechanical, optoelectronic, photocatalytic, piezoelectric, and thermoelectric properties of non-Janus and Janus diamanes monolayers named as C2H, C2F, C2Cl, C4HF, C4HCl and C4FCl. The structural stability is confirmed by cohesive energy, phonon dispersion spectra, and mechanical properties. The electronic properties has been calculated by HSE06 functional and the band gap are found to be 3.85, 5.64, 2.32, 4.16, 0.73 and 1.91 eV for C2H, C2F, C2Cl, C4HF, C4HCl and C4FCl, respectively. The hydrogen-containing non-Janus and Janus diamanes monolayers have a higher negative Poisson's ratio (NPR) and therefore are good auxetic materials. From the Poisson's ratio and Young's modulus of each configuration of non-Janus and Janus diamanes monolayer, anisotropic behavior was displayed. From the optical properties calculations, the refractive index values are around 1.5, which means that it will be a transparent monolayered materials. Also, C2Cl, C4HCl and C4FCl monolayers displayed high absorption spectra with an order of 105 cm−1 in the visible region, which shows great applications in optoelectronic devices. Additionally, the valence and conduction band-edge positions of 2D Janus and non-Janus diamanes of C2H, C2F, and C2Cl and C4HF monolayers have to straddle the redox potentials of water. It means that the photogenerated electrons and holes are sufficient to drive the overall water splitting. Whereas non-Janus diamanes C4HCl, and C4FCl monolayers displayed only water oxidation. The investigated in-plane piezoelectric coefficient has larger in non-Janus diamanes C4HF, C4HCl, and C4FCl monolayers. Therefore, it is very useful in the field of piezoelectric applications. From the thermoelectric properties, the non-Janus and Janus diamanes monolayers have great thermoelectric efficiency and were found to be 10.52 and 10.63% for C2H and C2F, respectively. Our results demonstrate the new class of 2D carbon-based monolayers has good auxetic materials as well as a wide range of applications in optoelectronics, piezoelectric, and thermoelectric fields.

Effective elastic properties of irregular auxetic structures

This paper presents an analytical framework with a bottom-up multi-step approach to predict the in-plane mechanical properties including the effective Young’s modulus and Poisson’s ratio in two directions. There are deviations for the analytical predictions with respect to the numerical results because of the simplifications of boundary conditions of the representative unit cell. To remedy the deviations, a modification coefficient is embedded to revise the analytical model. A finite element code for obtaining elastic properties of the irregular auxetic structures is developed to validate the revised analytical model. The good agreement between the revised analytical predictions and numerical results affirms the accuracy of the revised analytical model. It is noticeable that the effects of irregularity on the effective Young’s modulus are more prominent than on the Poisson’s ratio.

Experimental Characterization and Analysis of the In-Plane Elastic Properties and Interlaminar Fracture Toughness of a 3D-Printed Continuous Carbon Fiber-Reinforced Composite.

The use of continuous fiber as reinforcement in polymer additive manufacturing technologies enhances the mechanical performance of the manufactured parts. This is the case of the Carbon-Fiber reinforced PolyAmide (CF/PA) used by the MarkForged MarkTwo® 3D printer. However, the information available on the mechanical properties of this material is limited and with large variability. In this work, the in-plane mechanical properties and the interlaminar fracture toughness in modes I and II of Markforged’s CF/PA are experimentally investigated. Two different standard specimens and end-tabs are considered for the in-plane properties. Monolithic CF/PA specimens without any additional reinforcement are used for the interlaminar fracture toughness characterization. Two different mode I specimen configurations are compared, and two different test types are considered for mode II. The results show that prismatic specimens with paper end-tabs are more appropriate for the characterization of the in-plane material properties. The use of thick specimens for mode I fracture toughness tests complicates the characterization and can lead to erroneous results. Contrary to what has been reported in the literature for the same material, fracture toughness in mode I is lower than for mode II, which agrees with the normal tendency of traditional composite materials.

Investigation of in-plane heat distribution, thermal stability and mechanical properties of SS-(Fe3O4)/Ti/AlN/Ti/SiO2 as absorber coatings for efficient high temperature concentrated solar power systems

Despite numerous achievements recorded so far in developing solar absorber coatings for photothermal applications, the study of the thermal stability in humid and cold environment remains very scarce and the underlaying physics behind the transfer of the absorbed energy to the working fluid has never been investigated. In this perspective, we developed Ti/AlN/Ti/SiO2 film as multilayer selective solar absorber coating (MSSAC) on Fe3O4 modified stainless steel substrate using Direct Current (DC)/Radio Frequency (RF) magnetron sputtering at room temperature. The coating exhibited solar absorptance of 0.969 and thermal emittance of 0.220 in the solar and infrared spectrum regions respectively. The MSSAC was found to be thermally stable up to 500 °C in air. Further increase in annealing temperature to 600 °C resulted to a slight decrease in solar absorptance from 0.969 to 0.953 and a small rise in the emittance value from 0.220 to 0.258. A high humidity test and rapid heating-cooling cycling (RHCC) test revealed the stability of this coating and its potential application in humid (90 mmHg) and cold (− 50 °C) environments. Additionally, the coating shows good adhesion strength even after humidity and RHCC tests. The in-plane heat distribution analysis using thermal infrared imaging camera illustrated that there is a good possible transfer of the absorbed heat to the working fluid due to high surface temperature exhibited by Ti/AlN/Ti/SiO2 coated modified stainless steel (SS) substrate than the other boundary conditions. Overall, these results indicate that the present coating has the potential application in both high temperature, humid and cold environments.

Composites epoxídicos de fibra de carbono modificados con velos electrohilados de PA6 funcionalizados con nanopartículas

Epoxy resin composites inherent brittleness and poor crack resistance make necessary some form of toughening. Recently, several types of nanoparticles are being incorporated due to their theoretical high stiffness and strength. However, the addition of tougheners to the entire matrix resin could lead to a decrease in in-plane mechanical properties and to an increased viscosity of the system, being reduced the processing ability of matrix resin. Moreover, a homogeneous dispersion of these nanoparticles is still a problem. Thermoplastic nanofibrous structures can tackle these problems. They offer a solution for the dispersion issue, since they can be readily embedded in the resin and incorporate a nanosized phase in the composite. These nanofibres also do not increase the viscosity of the resin. Moreover, due to their macro scale length, no health hazards are involved in the production and use of these nanofibres. This paper investigates the effect of electrospun nanofibrous veils made of polyamide 6 modified with TiO2 nanoparticles on the properties of a carbon fibre/epoxy composite. The nanofibres were incorporated in the carbon fibre/epoxy composite as stand-alone interlayered structure during a vacuum infusion process. The effect of positioning these veils in different composite positions has been investigated. Incorporation of polyamide nanofibers increases the stress at failure and the Young’s modulus. Furthermore, mode I tests showed a slight improvement. When TiO2 modified veils are incorporated in the composite, similar mechanical properties were obtained, but new antibacterial properties were achieved when irradiated with UV light widening the application area of these composites.

Identification of printed circuit boards mechanical properties using response surface methods

PurposeThis study aims to discuss the determination of the unknown in-plane mechanical material properties of printed circuit boards (PCBs) by correlating the results from dynamic testing and finite element (FE) models using the response surface method (RSM).Design/methodology/approachThe first 10 resonant frequencies and vibratory mode shapes are measured using modal analysis with hammer testing experiment, and hence, systematically compared with finite element analysis (FEA) results. The RSM is consequently used to minimize the cumulative error between dynamic testing and FEA results by continuously modifying the FE model, to acquire material properties of PCBs.FindingsGreat agreement is shown when comparing FEA to measurements, the optimum in-plane material properties were identified, and hence, verified.Originality/valueThis paper used FEA and RSMs along with modal measurements to obtain in-plane material properties of PCBs. The methodology presented here can be easily generalized and repeated for different board designs and configurations.

Tuning interlaminar fracture toughness of fine z-pin reinforced polymer composite

This paper aims to improve the interlaminar fracture toughness of carbon fiber reinforced polymer (CFRP) composites by implanting fine z-pins with the minimum damage on in-plane fibers. Z-pins with diameters as small as 0.1 mm and 0.2 mm were prepared by using carbon fiber tows with different mechanical properties. The effect of the mechanical property of carbon fiber pin on the interlaminar fracture toughness of composite laminate was investigated to reveal the enhancement mechanism. The results show that fine z-pins significantly improve the interlaminar fracture toughness and simultaneously are favorable for maintaining high retentions of in-plane mechanical properties of composite laminate. Compared with control sample, the propagation GIC values of CFRPs implanted with 0.2 mm and 0.1 mm CCF800 z-pins increase by 276 % and 541 % respectively at a low pin volume fraction of 0.16 vol%. Both z-pin pull-out and z-pin fracture failure behaviors can be observed for these fine z-pin reinforced composites. The higher tensile properties of z-pins and better transverse shear resistance tend to result in the failure of z-pin pull-out. With the decrease of z-pin diameter, the probability of z-pin fracture failure becomes greater, and correspondingly stronger pinning effect and larger failure load are achieved.

Enabling Selectively Tunable Mechanical Properties of Graphene Oxide/Silk Fibroin/Cellulose Nanocrystal Bionanofilms.

Enhancing and manipulating the mechanical properties of graphene oxide (GO)-based structures are challenging because the GO assembly is easily delaminated. We develop nacre-like bionanofilms whose in-plane mechanical properties can be manipulated through water vapor annealing without influencing their mechanical properties in the thickness direction. These bionanofilms are prepared from GO, silk fibroin (SF), and cellulose nanocrystals (CNCs) via a spin-assisted layer-by-layer assembly. The postannealing mechanical properties of the films are determined with atomic force microscopy (AFM) bending and nanoindentation, and it is confirmed that the mechanical properties of the bionanofilms are altered only in the in-plane direction. While AFM bending shows Young's moduli of 26.9, 36.3, 24.3, and 41.4 GPa for 15, 15 annealed, 30, and 30 annealed GO/SF/CNC trilayers, nanoindentation shows reduced moduli of 19.5 ± 2.6 and 19.5 ± 2.5 GPa before and after annealing, respectively. The unaltered mechanical properties of the bionanofilms along the thickness direction after annealing can be attributed to the CNC frame in the SF matrix acting as a support against stress in the thickness direction, while annealing reorganizes the bionanofilm structure. The tunability of the bionanofilms' mechanical properties in only one direction through structure manipulation can lead to various applications, such as e-skin, wearable sensors, and human-machine interaction devices.