Image Correlation Analysis Research Articles

Comparative study of failure mechanism of CFRP partially confined normal strength concrete (NSC) and UHPC cylinders under axial compression

Ultra-high performance concrete (UHPC) holds significant potential in marine structures due to its superior compressive strength and enhanced durability in comparison to normal strength concrete (NSC). Carbon fiber-reinforced polymer (CFRP) confinement has been proven to improve these properties further. However, the compressive behavior of CFRP-confined UHPC, especially for partial confinement, presents complexities arising from the intricate interaction mechanism between UHPC and wrapped CFRP strips. To address this issue, the present study conducted axial compression tests accompanied by digital image correlation (DIC) analyses. Failure modes, stress-strain behavior, hoop strain distribution, and cracking evolution of CFRP partially confined NSC/UHPC were elucidated, thereby uncovering the underlying load transfer mechanism between NSC/UHPC and wrapped CFRP strips. Research outcomes show that the enhancement in compressive strength fcc/fco (0.99 ∼ 1.43) and strain εcu/εco (1.51 ∼ 2.59) of CFRP partially confined UHPC is relatively lower than the NSC counterparts (1.28 ∼ 2.98 and 3.82 ∼ 15.14, respectively). Moreover, lower hoop strain efficiency εh,rup/εfrp can be found for CFRP partially confined UHPC compared to NSC (0.61 vs. 0.86). These phenomena were primarily attributed to the localized shear-cracking pattern and low dilation behavior of confined UHPC. Based on the experimental results, the elucidation of the underlying load transfer mechanism between UHPC/NSC and wrapped CFRP strips provides valuable insights into comprehending the compressive behavior of CFRP partially confined UHPC. Finally, the “arching effect” is found to exhibit limited effect on the ultimate condition’s prediction of partially confined UHPC according to the failure mechanism and Li et al.’s model can reliably predict the ultimate conditions among the existing models.

Integrated testing and modelling of substructures using full-field imaging and data fusion

A new integrated testing and modelling paradigm based on full-field imaging and finite element (FE) analysis that utilises full-field data fusion is proposed for structural evaluation and model validation at substructure level. The approach is developed for the assessment of a composite wind turbine blade (WTB) substructure subjected to multiaxial loading, mimicking in-service conditions, using a new reconfigurable loading rig. A steel mock-up equivalent to the WTB substructure was used to demonstrate the new experimental, numerical, full-field imaging, and data fusion approaches. Digital Image Correlation (DIC) and Thermoelastic Stress Analysis (TSA) were used to obtain the complex load response of the substructure. Strains and displacements derived from DIC were fused with numerical predictions obtained using a FE-based stereo-DIC simulator, which provided unparalleled like-for-like data comparisons. A numerical FEA solution for TSA was also obtained that accounts for heat transfer and allowed an independent means of structural evaluation. The challenges of deploying full-field imaging on the substructure scale are highlighted alongside procedures for mitigating multiple deleterious effects that are concatenated in large structures testing. It is demonstrated that high quality and fidelity experimental data can be obtained and fused with numerical models to provide a comprehensive and quantitative structural assessment at the substructure scale. It is shown that the proposed full-field data fusion efficiently reveals uncertainties in both the models and experiments. The work provides important steps to support virtual testing at higher length scales and their integration into the design, development, and certification programs of next generation, high-performance structures.

Tensile Fracture Initiation and Propagation of Granite and Gneiss at Wedge Splitting Tests: Part 2—Fracturing Studies Based on Digital Image Correlation and Thin Section Analysis

AbstractThe crack development in quasi-brittle granite and brittle gneiss under mode I loading condition was monitored using digital image correlation (DIC) technique during wedge splitting tests. The cracking behavior was studied on granite specimens that were split in one material direction, perpendicular to the rift plane, and gneiss specimens that were split in three different material directions, parallel and perpendicular to the foliation (along and across a lineation). The granite specimens had a saw cut 5 mm-wide notch and a blunt round notch in form of a 32 mm borehole. The gneiss specimens had a saw cut notch. The results from the DIC measurements revealed a meandering and branching crack path for the granite, whereas a smoother crack path for the gneiss with almost no branching. This behavior was confirmed by microscopy images from thin sections taken from specimens after testing. The thin sections showed that the fractures were prone to propagate across grains in the more coarse-grained granite than in the fine-grained gneiss, where the fractures propagated almost entirely along grain boundaries. The crack initiation occurred mainly in the corner of the saw cut notches and centrally in the round notch. However, the initiation locations in the granite were affected by the medium- to coarse-grained microstructure with grains preventing initiation and propagation which yielded displaced positions out from the ideal ones with respect to the highest stress in some cases. The crack opening displacement was determined along the crack path from the DIC measurements at 12 stages on each specimen of the advancing crack during the splitting progress. The critical crack opening displacement and length of the fracture process zone were assessed and the crack front position yielding the crack length along the tests was determined. The results showed a critical crack length when the deformations in the ligament (also called plastic hinge) affected the cracking process. The average crack velocity in gneiss during the test was more than twice as high as in the granite. This is attributed to a combined effect of the higher brittleness in the gneiss and the effect of a too large elastic energy in the specimen and test setup in relation to the dissipated fracture energy which made the initial crack propagation in the gneiss specimens nearly unstable. The strain energy release rate was calculated along the crack propagation and showed a lower value when the crack lengths were less than 40–60 mm. The calculation of the strain energy release rate was made on crack length measurements from DIC results. The results from the investigation were discussed in relation to the few other similar results found in the literature. The findings give an insight and understanding of the cracking process via both qualitative and quantitative results. Several used methods were novel or not used together in a single study as in this one.

In situ SEM analysis of cracking and its quantitative link to resistance evolution in uniaxially stretched nanocomposite inks

Nanocomposite conductive inks consisting of metal flakes embedded in a polymer binder are employed as interconnect materials in flexible hybrid electronics (FHE) devices. Crack formation has been hypothesized to play a key role in the ink's electrical degradation (increase of resistance), but the two have not been directly correlated. To address this gap, two classes of inks are studied using uniaxial stretch experiments, with in situ SEM imaging, and synchronous electrical resistance measurement. In plane strain maps obtained from digital image correlation (DIC) analysis of wide-field SEM images (∼300 μm in width) identify crack patterns at various applied strains. From these strain maps, crack length measurements are obtained. A finite-element based numerical model adapted for non-uniform crack lengths is used to predict normalized resistance increase from the crack lengths. The model predictions are compared against the experimentally measured resistance changes. There is a remarkable correlation between the predicted and experimentally measured normalized resistance values. The linear crack density was also used to help understand the relation between the effective crack length and resistance increase. Closeup images of the ink top surface and the ink cross-section during the in situ SEM stretch experiment are used to explain differences between predicted and measured normalized resistance.

Comparison of mode II delamination behaviours in multidirectional and unidirectional composite laminates

Multidirectional (MD) composite laminates are extensively employed in structural applications owing to their superior mechanical characteristics. Nevertheless, the evaluation of the fracture toughness of composite laminates primarily relies on tests using unidirectional (UD) specimens. This study evaluates the reliability of characterizing mode II delamination behaviour in MD laminates by using UD specimens. The quantification of delamination area through Digital Image Correlation (DIC) analysis is integrated with a physical Energy Release Rate (ERR) method to ascertain the fracture resistance, which is compared with the ERR derived via a modified J-integral method and the standardized compliance methods. Fractographic analysis reveals similar fracture mechanisms in specimens with identical interfaces. The physical ERR increases notably due to large-scale fibre bridging induced by fibre nesting at 0∘//0∘ interfaces. Conversely, in 0∘//90∘ interfaces, large-area matrix cracking enhances the intrinsic fracture resistance, excluding the extrinsic toughening provided by fibre bridging.

Mechanical properties and crack deflection mechanisms in 3D-Printed porous geopolymers with cellular structures

ABSTRACT This study focuses on using helical design patterns via 3D printing to create geopolymer with a highly porous structure in order to enhance their strength-density relationship and fracture properties. In this regard, to create porous structure, different pitch angles and infill densities were chosen, and mechanical and fracture properties were examined. The results of mechanical strength tests revealed that while the pitch angle does not significantly affect compressive strength, flexural strength is improved by implementing a low pitch angle helical structure, which leads to the strength-density relationship improvement. Additionally, the work of fracture results demonstrated an enhancement for samples with low pitch angles, such as α15° and α30°, compared to cast and non-directional printed samples. The digital image correlation and fracture surface analysis showed several fracture mechanisms, predominantly crack deflection and twisting, in samples with low pitch angles, which contributes to the observed improvements in the work of fracture.

Analytic modeling and validation of strain in textile-based OLEDs for advanced textile display technologies

In the IoT era, the demand for wearable displays is rapidly growing, catalyzing the advancement of research into textile-based organic light-emitting diodes (OLEDs). This growing interest stems particularly from the inherent flexibility of textile-based OLEDs1,2, allowing for seamless integration into the dynamic and interactive functionalities of cutting-edge wearable technology, alongside their superior electrical performance. The durability and mechanical robustness of these displays, especially under physical stress and deformation, are critical to their practical application and longevity. Thus, understanding and enhancing the mechanical properties of textile-based OLEDs is paramount for their successful integration into wearable technologies. However, many studies assessing the mechanical properties of OLEDs have predominantly relied on simplistic bending test outcomes determined by the radius, often neglecting or insufficiently analyzing the strain exerted on the OLEDs atop textile substrates in relation to curvature of these devices. Existing analyses typically presume pure bending, though such an assumption leads to considerable errors in strain estimations, making such approaches problematic if the goal is practical application in actual wearable display products. To address these limitations, an analytic model that includes a comprehensive energy equation is introduced, considering the stretching energy, bending energy, and shear energy of each layer composing the textile substrate. This holistic approach provides a novel formula specifically designed to calculate the top surface strain of textile substrates. Robust validation of this formula is conducted by comparing its results with strain measurements obtained from digital image correlation (DIC) and finite element analysis (FEA) outcomes from ANSYS across various bending radii (or equivalently, curvatures). The close alignment of the calculated strain values with those derived from DIC and FEA not only underscores the precision of this formula but also highlights its significant potential for enhancing the designs and functionalities of future wearable display technologies under real-world conditions.

Experimental Investigation on Rock Failure Characteristics of Large-Span Goafs Using Digital Image Correlation Analysis and Acoustic Emission Monitoring

Rockmass in deep mining is highly susceptible to large-scale collapses under high stress and blast-induced disturbances, leading to casualties and economic losses. To investigate the evolution characteristics of goaf instability and the types of seismic sources that induce instability, an experiment on goaf instability was designed under uniaxial compression conditions based on actual mining operations. The entire experimental process was monitored using digital image correlation analysis and acoustic emission monitoring. By calculating the digital speckle field on the surface of the rock specimen during the experiment, the evolution characteristics of the deformation and strain fields from the beginning of loading to complete failure were analyzed. The study explored the dynamic behavior of cracks from initiation to propagation and eventually inducing large-scale collapse. The results show that the instability process of the goaf begins with the formation of tensile cracks. As stress increases, shear cracks occur in the specimen, leading to macroscopic failure. Furthermore, based on the differences in overall microfracture types measured by RA-AF characteristic parameters during specimen failure, large amplitude acoustic emission events corresponding to the formation of dominant macroscopic cracks were selected, and the focal mechanisms of these events were inverted. The results indicate that shear failure sources are significantly more prevalent than tensile failure sources in acoustic emission events leading to goaf instability. These findings can provide useful guidance for the support design and the prevention and control of rockmass instability disasters.

Low-cycle fatigue properties and fracture location transition mechanism of dissimilar steel welded joints in towers of wind turbines

This study investigates the low-cycle fatigue (LCF) behavior of two types of dissimilar steel welded joints (DSWJs): AISI 1035 & S550Q and AISI 1020 & S550Q. Digital image correlation (DIC) and finite element analysis (FEA) were used to analyze the heterogeneous strain distribution. The results reveal that the location of maximum strain, which is load-dependent and related to strength mismatch, corresponds to the fracture location of the LCF specimens. Specifically, the crack initiation site shifts from the weld toe to the base metal as strain increases. Moreover, the weld reinforcement of the DSWJs significantly affects the failure site transition, introducing strain concentration at lower stress levels while enhancing deformation resistance at higher stress levels, as evidenced by DIC strain measurements and FEA. These findings highlight the importance of joint reinforcement profile, strength mismatch and external load level in designing DSWJs for wind turbine towers against LCF failure.

Material volume reduction for creep testing using composite cantilevers and its application for residual life assessment

Digital image correlation (DIC) and finite element analysis (FEA) demonstrate that creep deformation in bending occurs primarily in ≈30 % of the cantilever volume near the fixed end, especially when the creep stress exponent ranges from 5 to 7. As an alternative approach to minimize the material volume required for testing, the concept of fabricating composite cantilevers is proposed and validated in this study. A composite cantilever sample consists of an “active” creeping portion (e.g., T22 boiler steel) and an additively extended “passive” non-creeping portion (e.g., IN718). The volume reduction process involved varying the length of the “active” section, a, while keeping the total length of the cantilever, L, constant. The DIC measurements conducted at 600 °C to assess the creep behavior of T22 steel revealed that analytical expressions for monolithic cantilevers could aptly predict the constitutive steady-state creep laws from the composite cantilevers if measurements are made in a region at a critical distance away from the interface. FEA indicates that accurate stress estimation enables predicting monolithic creep behavior using composite samples with “a/L” ratios of as small as 5 %. Using the developed approach, the loss of creep resistance of T11 boiler steel that was in service for ∼ 240,000 h was ascertained in high throughput fashion using a composite cantilever having only 30 vol % of the “active” material. Guidelines to minimize the volume fraction of the “active” portion in the composite cantilever and the implications of the observations for estimating the residual life of in-service high-temperature components are discussed.

Multiscale evaluation of sand-geomaterial interface shear response in terms of material geometry effects

This study evaluates the effects of particle and surface geometric features on the interface shear behavior of sand-geomaterial. Particle shape and size were adjusted for the sand, and surface roughness form and height were set for the geomaterial part. 3D printing technology was used to produce geomaterials in the desired form. A custom-made transparent interface shear box was developed to perform digital image processing. For macroscale response, peak and residual strengths and dilation angle were measured. Sliding percentage and shear band thickness were determined from digital image correlation analyses for the mesoscale response. The experimental results showed that the macroscale response parameters increased as the overall regularity of the sand particles decreased. The increase in mean particle size and roughness height led to an increase in macroscale parameters. Digital image correlation analyses showed that the sliding percentage had an inverse correlation with the shear band thickness in terms of the particle shape and the roughness height effects. The roughness form controlled the trend of mean particle size effects on the sliding percentage. Overall, the mesoscale parameters revealed the traces of interlocking response, particle kinematics, and the failure mechanism in the interface region. Thus, a bridge was established between meso- and macro-scale responses.

Thin-layer Ultra-High-Strength Engineered Cementitious Composites (UHS-ECC) reinforced with small-diameter FRP bars for structural strengthening

This study proposed a novel strengthening system for reinforced concrete (RC) structures using a thin layer of Ultra-High-Strength Engineered Cementitious Composites (UHS-ECC) reinforced with small-diameter Fiber-Reinforced Polymer (FRP) bars. Experimental investigation, digital image correlation analysis, and numerical simulation were conducted to evaluate the flexural performance and failure mechanism of RC beams strengthened with 20-mm UHS-ECC layers and 3-mm FRP bars. It was found that the 20-mm UHS-ECC layer alone improved the load capacity of RC beams by 8.3 %, though with reduced deflection, whereas incorporating two 3-mm FRP bars increased load capacity by up to 40.4 %, without sacrificing deflection. Failure in all specimens was caused by concrete crushing; however, FRP-reinforced UHS-ECC layers mitigated early crack localization, significantly enhancing both strength and ductility. This study also revealed that cast-in-place FRP-reinforced UHS-ECC layers exhibited higher load capacity and could avoid ECC/concrete interfacial cracks compared to epoxy-bonded prefabricated layers. A three-dimensional finite element model was proposed for the strengthening system, and the flexural behavior was successfully predicted. It is revealed that the FRP-to-UHS-ECC bond had a marginal influence on performance, while the bond at the UHS-ECC-to-concrete interface significantly impacted flexural behavior. Remarkably, the small-diameter FRP bar achieved 75 % of its tensile strength at the ultimate stage. These findings underscore the potential of FRP-reinforced UHS-ECC layers as an effective solution for enhancing the mechanical and durability performance of RC structures.

Ground failure and soil erosion caused by bursting of buried water pipeline: experimental and numerical investigations

Pressurized water pipelines buried in an urban environment are prone to bursting failures, threatening public safety and traffic convenience. The limited studies in literature just focused on soil fluidization while few studies considered ground failure, shear strain, soil erosion and the influence of leakage locations during pipe bursts. In this study, extensive experimental tests along with a finite difference method – discrete element method (FDM-DEM) solid–fluid coupling analysis were conducted to investigate these issues. It was disclosed that the failure development during pipe bursts can be divided into three stages, i.e., seepage diffusion, erosion cavity expansion, and soil fluidization. By digital image correlation (DIC) analysis of the experimental results, a wedge-shaped displacement zone in ground was identified, with peak shear strain near its boundaries. Moreover, it was revealed that leakage locations affected the expansion origin of erosion cavity; as the burial depths increased, the ground heave range increased linearly; the maximum water outflow distance was closely related to the internal pressures of buried pipeline, which could be modeled by a square root formula based on turbulent jet theory. Mesoscopic analyses revealed that finer particles were more susceptible to erosion during pipe bursts because of the low possibility of forming strong connections with surrounding particles. The findings yielded from this study can enhance the understanding of pipe bursts and help professionals mitigate potential damage.

Study on tensile damage evolution of Ti6Al4V alloy based on DIC technique

Abstract Both optical microscopy (OM) and scanning electron microscopy (SEM) were used to analyze the microstructure of the Ti6Al4V alloy and evaluate its tensile damage behavior. Using Lemaitre’s definition of damage, the variation rule of damage during the reduction of elastic modulus was obtained. Combining the digital image correlation (DIC) analysis approach allowed for an experimental investigation of the alloys’ tensile mechanical characteristics. The strains at 500 independent points were extracted using VIC-2D software. The damage factor of the whole strain field was established by equations and 3D graphics, and the damage evolution process was visualized and analyzed. The results show that the Ti6Al4V alloy has good plasticity, and its fracture mode is a ductile fracture. The sample’s modulus of elasticity falls, and the extent of damage increases as the stretching continues. The sample undergoes a localized violent deformation during the tensile process, as opposed to a homogenous deformation state. The harm progressively concentrates and increases at an increased rate.

Digital Image Correlation Analysis of Fatigue Degradation of Layered Polymer Composites (Polyetheretherketone/Polyetherimide, PEEK/PEI) with Carbon-Fiber Fabric Prepreg

In this work, the relationship was considered between the structure and cyclic loading resistance of a layered composite consisting of PEI (PEEK) plate/PEI (PEEK) film/PEI-impregnated carbon-fiber fabric prepreg/PEI (PEEK) film/PEI (PEEK) plate by analyzing the time variation in the parameters of mechanical hysteresis loops calculated using digital image correlation. It was shown that the polyetherimide-based layered composite has low fatigue life under cyclic loading (0.8 of the yield strength), resulting from incompatible deformation between the PEI plates and the prepreg due to a layer interface formed by low-melting TecaPEI film. In the PEEK layered composite, the layer interface was formed by neat PEEK energy director and therefore had a little amount of defects, due to which the load was well transferred from the PEEK plates to the middle reinforcement layer. As a result, the fatigue life at a load level of 0.8 of the yield strength corresponded to high-cycle fatigue (more than 86000 cycles).

Damage identification in composite structures using high-speed 3D digital image correlation and wavelet analysis of mode shapes

ABSTRACT In this study, the damage identification procedure combining the advantages of high-speed 3D digital image correlation (DIC) that is used for modal analysis and wavelet-based processing algorithm is presented. The proposed procedure has been successfully validated on sandwich composite structures with internal damage of a core and impact damage, and its performance was demonstrated by detection, localisation, and identification of shapes of damage in tested structures, comparable to the results from scanning laser Doppler vibrometry (SLDV). The effectiveness in damage identification was achieved by the development of processing algorithm of acquired mode shapes, which uses a 2D double-density directional wavelet transform with increased sensitivity with entropic weights allowing to automatically select those wavelet coefficients and mode shapes, which are most sensitive to damage. The procedure presented in this paper demonstrates the performance of 3D DIC for damage identification as a cost-effective alternative to the procedures based on SLDV measurements.

Achieving superior strength and ductility synergy in bulk ultrafine grained Al-Mg-Sc-Zr alloy via powder pre-aging

Introducing high density of nano-precipitates to recrystallized ultrafine grains is helpful to realize strength-ductility synergy but is a challenging task, because recrystallization and precipitate growth/coarsening usually concur. Here we develop a pre-aging powder metallurgy processing route to achieve such microstructure in Al-Mg-Sc-Zr alloy. During the pre-aging stage, atomic clusters including short-range order are formed within the grains, which provide new sites for the nucleation and enable the formation of fine Al3(Sc, Zr) precipitates. Subsequent high-temperature sintering and hot extrusion lead to grain recrystallization. The nano-precipitates not only further strengthen the ultrafine-grained alloy by Orowan mechanism, but also greatly enhance the strain-hardening rate by dislocation-precipitate interaction, resulting in excellent strength-ductility synergy. The utilization of digital image correlation (DIC) analysis allows for the observation of dynamic strain aging during the tensile process, whereby the strain demonstrates a distinctive step-like transition coinciding with the passage of the Portevin-Le Chatelier (PLC) band. This work provides a new path for improving the mechanical properties of the same type of metallic materials.

Quantitative evaluation of local strain distribution induced by deformation twins and triggering effect of deformation twinning on neighboring grains in polycrystalline AZ31 magnesium alloys

{101‾2}<1‾011> deformation twinning commonly occurs in Mg/Mg alloys. In their polycrystals, however, twinning is not always activated at locations with high Schmid factor for {101‾2}<1‾011> twinning. It is believed that twinning behavior in polycrystalline Mg/Mg alloys can be understood with a consideration of interaction between adjacent twins as well as local deformation behavior on a micro- and meso‑structural scale. In this study, we theoretically estimate local plastic strain within twins by transforming coordinates and then compare it with that experimentally obtained from digital image correlation (DIC) analysis for understanding the reason for non-Schmid twinning in polycrystalline-Mg alloys. The theoretically estimated strain of twins was found to be in good agreement with the DIC-strain value. Furthermore, it was observed that the variant selection of twin can be explained by the compatibility parameter m’, rather than Schmid factor, suggesting that twin activation in polycrystalline-Mg is strongly influenced by adjacently appeared twins.

Fracture mechanism and ductility performances of fiber reinforced shotcrete under flexural loading insights from digital image correlation (DIC)

This paper investigates the fracture mechanism and ductility performance of fiber-reinforced shotcrete (FRS) under flexural loading through digital image correlation (DIC) analysis. The focus is on determining the optimal mix design, utilizing recycled and manufactured fibers in shotcrete through four-point bending tests. These tests reveal significant improvements in flexural strength and ductility, as well as crack resistance, attributed to the synergistic effect of both types of fiber in hybrid fiber reinforcement. Notably, the inclusion of recycled fibers from automobile tires enhances mechanical characteristics and impact resistance, contributing to environmental sustainability and cost reduction. DIC analysis offers crucial insights into crack initiation and propagation in shotcrete, highlighting the impact of fiber reinforcement on crack patterns. Manufactured fibers delay crack onset effectively, while hybridization enhances fracture characteristics, offering improved crack control and flexural strength. The study underscores the potential of hybrid fiber mixes for enhancing structural performance in tunnel support applications, emphasizing the synergistic effect of hybrid of different fiber types. Overall, the research contributes to advancing understanding of fracture behavior in fiber-reinforced shotcrete and provides practical insights for optimizing mix designs to achieve superior mechanical properties and durability.

Strain rate sensitivity of rotating-square auxetic metamaterials

This study provides an in-depth analysis of the mechanical behavior of rotating-square auxetic structures under various strain rates. The structures are fabricated using stereolithography additive manufacturing with a flexible resin. Mechanical tests performed on structures include quasi-static, intermediate, and high strain rate compression tests, supplemented by high-speed optical imaging and two-dimensional digital image correlation analyses. In quasi-static conditions (5 × 10–3 s-1), multiscale measurements reveal the correlation between local and global strains. It is shown that cell hinges play a significant role in structural deformation and load-bearing capacity. In drop tower impact conditions (intermediate strain rate of ca. 200 s-1), the auxetic structures display significant strain rate hardening compared to loading at quasi-static rates. The thin-hinge structures maintain a Poisson's ratio of approximately -0.8, showing higher auxeticity than slow-rate compression tests. High strain rate conditions (ca. 2000s-1) activate additional deformation mechanisms, including a delayed state of equilibrium exemplified by a heterogeneous distribution of lateral strains, possibly due to stress wave interactions and inertial stresses. The study further reveals nonlinear correlations between Poisson's ratio, strain, and strain rate, indicating reduced auxeticity at higher strain rates. These observations are discussed in terms of complex wave interactions and the strain rate hardening characteristics of the base polymer.