Force-displacement Data Research Articles

A Pragmatic Approach for the Evaluation of Depth-Sensing Indentation in the Self-Similar Regime

Abstract This work evaluates and revisits elements from the depth-sensing indentation literature by means of carefully chosen practical indentation cases, simulated numerically and compared to experiments. The aim is not to provide a comprehensive study, but to close a series of debated subjects, which constitute major sources of inaccuracies in the evaluation of depth-sensing indentation data in practice, with the help of illustrative examples. First, own examples and references from the literature are presented in order to demonstrate how crucial self-similarity detection and blunting distance compensation are, for establishing a rigorous link between experiments and simple sharp indenter models. Moreover, it is demonstrated, once again, in terms of clear and practical examples, that no more than two parameters are necessary to achieve an excellent match between a sharp indenter finite element simulation and experimental force–displacement data. The clear conclusion is that reverse analysis methods promising to deliver a set of three unique material parameters from depth-sensing indentation cannot be reliable. Lastly, in light of the broad availability of modern finite element software, we also suggest to avoid the rigid indenter approximation, as it is shown to lead to unnecessary inaccuracies. All conclusions from the critical literature review performed lead to a new semi-analytical reverse analysis method, based on available dimensionless functions from the literature and a calibration against case specific finite element simulations. Implementations of the finite element model employed are released as supplementary material, for two major finite element software packages.

Machine Learning in Model-free Mechanical Property Imaging: Novel Integration of Physics With the Constrained Optimization Process

The Autoprogressive Method (AutoP) is a fundamentally different approach to solving the inverse problem in quasi-static ultrasonic elastography (QUSE). By exploiting the nonlinear adaptability of artificial neural networks and physical constraints imposed through finite element analysis, AutoP is able to build patient specific soft-computational material models from a relatively sparse set of force-displacement measurement data. Physics-guided, data-driven models offer a new path to the discovery of mechanical properties most effective for diagnostic imaging. AutoP was originally applied to modeling mechanical properties of materials in geotechnical and civil engineering applications. The method was later adapted to reconstructing maps of linear-elastic material properties for cancer imaging applications. Previous articles describing AutoP focused on high-level concepts to explain the mechanisms driving the training process. In this review, we focus on AutoP as applied to QUSE to present a more thorough explanation of the ways in which the method fundamentally differs from classic model-based and other machine learning approaches. We build intuition for the method through analogy to conventional optimization methods and explore how maps of stresses and strains are extracted from force-displacement measurements in a model-free way. In addition, we discuss a physics-based regularization term unique to AutoP that illuminates the comparison to typical optimization procedures. The insights gained from our hybrid inverse method will hopefully inspire others to explore combinations of rigorous mathematical techniques and conservation principles with the power of machine learning to solve difficult inverse problems.

Nonlinear Finite Element Load-Displacement Model and Analysis of Circular-Axis Hinge, Self-Similar Mechanism With Large Out-of-Plane Motion

Abstract This research studies the large-displacement response of a fractal-architecture mechanism with circular-axis flexible hinges by formulating an efficient and accurate nonlinear finite element model. Two three-dimensional line elements are proposed whose nodal degrees-of-freedom include the three spatial Tait–Bryan angles. The nonlinear finite element is generated using the minimum potential energy condition for the entire deformed structure in a non-incremental approach. The error does not depend on the number of load steps since one step is sufficient to achieve the final, deformed state. The method is applied to predict the nonlinear, large, out-of-plane displacement of the fractal-hinge compliant mechanism. The model predictions are validated by finite element code simulation and experimental testing. The nonlinear finite element force-displacement data coincide with the linear compliance model predictions of Lobontiu et al. (2019, “Stiffness Design of Circular-Axis Hinge, Self-similar Mechanism With Large Out-of-Plane Motion,” ASME J. Mech. Des., 141(9), p. 092302) for approximately one-fourth lower portion of the load range and display the expected hardening-spring features for the load range remainder.

A validated lateral response model for mass timber frames with knee-braces

Efforts to increase the use of renewable materials in construction are pushing the use of timber frames into new boundaries—for example, as lateral load-resisting systems in medium to high-rise buildings. This drive brings forth higher performance requirements for timber structures against hazards such as fires and earthquakes. The present study focuses on the development and parameter calibration of a cyclic lateral response model for mass timber frames with knee-braces (MTF-KBs) through a full-scale test. The model primarily comprises plastic hinges, which represent the hysteretic behavior of the MTF-KB specimen. The model parameters are estimated from test data using a Particle Filter (PF) method, which yields the optimal parameters together with their uncertainties. The calibrated model is then used in parametric studies to examine their lateral response, including stiffness and strength degradation, and damage evolution. The performance of MTK-FB in various single- and multi-story structural configurations is also investigated based on this calibrated model, and a novel energy-based damage index is devised that maps visual observations to various thresholds of damage. The proposed MTK-FB model can be readily recalibrated to new/other experimental data. Moreover, the PF-based model updating method presented in this study can be applied to any hysteretic force-displacement data that exhibit complex behavior such as cycle degradation, inelastic deformations, and pinching. The availability of model parameter uncertainties is a useful feature for performance-based seismic assessment studies.

Simultaneous Regression and Selection in Nonlinear Modal Model Identification

High fidelity finite element (FE) models are widely used to simulate the dynamic responses of geometrically nonlinear structures. The high computational cost of running long time duration analyses, however, has made nonlinear reduced order models (ROMs) attractive alternatives. While there are a variety of reduced order modeling techniques, in general, their shared goal is to project the nonlinear response of the system onto a smaller number of degrees of freedom. Implicit Condensation (IC), a popular and non-intrusive technique, identifies the ROM parameters by fitting a polynomial model to static force-displacement data from FE model simulations. A notable drawback of these models, however, is that the number of polynomial coefficients increases cubically with the number of modes included within the basis set of the ROM. As a result, model correlation, updating and validation become increasingly more expensive as the size of the ROM increases. This work presents simultaneous regression and selection as a method for filtering the polynomial coefficients of a ROM based on their contributions to the nonlinear response. In particular, this work utilizes the method of least absolute shrinkage and selection (LASSO) to identify a sparse set of ROM coefficients during the IC regression step. Cross-validation is used to demonstrate accuracy of the sparse models over a range of loading conditions.

Damaged and failure characterization of 7075-T6 Al alloy based on GISSMO model

Failure simulation of 7075-T6 Al alloy is very important due to its relatively low ductility compared to conventional steel. A hybrid numerical-experimental method was developed to determine plastic strains at fracture as a function of triaxiality. The uniaxial tension tests were performed by using the specimens including pure shear, 45° shear, smooth, R5 notch and R15 notch. The fracture locus was established by calibrating the parameters of the Hosford-Coulomb fracture model and was implemented into the GISSMO damage model. The results showed that the predicted force-displacement data were in good agreement with the experimental results. The results of the mesh dependence showed that the mesh size in the range of 0.5–5 mm did not have much influence on the damage results. To assess the accuracy of the damage model, three-point bending tests of the anti-collision beam were performed. The calibrated GISSMO damage model could accurately predict the load-displacement data.

A numerical study of the constitutive characterization of thermoplastic materials submitted to finite strain

The mechanical characterization of thermoplastics submitted to finite strain is a non-trivial procedure since they may present necking and cold-drawing. These phenomena are associated with heterogeneous strain fields that may mask the real stress–strain curve and lead to mistaken conclusions about the capability of constitutive models to represent the material mechanical response. Aiming to shed light on this issue, this paper presents a numerical study based on a Finite Element Method Updating (FEMU) technique to obtain the true stress–strain curve of a thermoplastic specimen. FEMU technique is employed to characterize three elastoplastic models with different mathematical frameworks. Inverse problems are constructed considering force response and displacement data of a heterogeneous strain field on the specimen due to the necking and neck propagation kinematics. Results shown that even a very simple multilinear elastoplastic model, available in commercial software, is capable of representing force response of a tensile test when only experimental force data is considered. However, when the necking kinematics is taken into account, the studied models present different results and poor mechanical behavior representation, indicating that only the force data obtained from a tensile test is not enough to establish conclusions about the performance of a constitutive model when heterogeneous strain field occurs. Since none of the models was capable of accurately reproduce the experimental force and kinematics data, to evaluate which model performs better, it is proposed a multi-objective analysis of Pareto front results.

A novel technique for dynamic shear testing of bulk metals with application to 304 austenitic stainless steel

This paper describes a new single-shear specimen (SSS) and method to characterize the dynamic shear behavior of bulk metals using a traditional Split Hopkinson Pressure Bar (SHPB). By this method, the shear behavior of materials can be tested conveniently over a wide range of strain rates within 105 s−1. This technique was applied to a 304 austenitic stainless steel (ASS) under shear strain rates from 0.001 s−1 to 38700 s−1 at room temperature. Based on finite element (FE) simulations, it was found that the deformation of the specimen shear zone was dominated by shear stress/strain components. Stress state parameters represented by stress triaxiality η and Lode angle parameter θ- were found very close to zero, indicating a deformation mode of simple shear. Besides, an obvious gap existed between the local deformation behavior in the specimen shear zone and the macroscopic stress-strain relations measured by the strain gauges on the SHPB bars. A correction coefficient method was adopted to extract the real shear behavior from the experimentally obtained force-displacement data. Through comparisons between the tested and simulated stress-strain curves, a good agreement was obtained.

Evaluation of Lactose-Based Direct Tableting Agents' Compressibility Behavior Using a Compaction Simulator.

A compaction simulator (CS) is a single-punch instrument that records data during the powder compaction process. The aim of the study was to determine the behavior of lactose-based direct tableting agents (DTAs) by CS. The data recorded were used to evaluate the flowability and compressibility of powders. The focus of the study was on comparing the compressibility of StarLac® [alpha lactose monohydrate (85%) and white maize starch (15%)] and FlowLac®100 (spray-dried alpha lactose monohydrate) in order to make tablets containing poorly flowable paracetamol. Two lactose-based DTAs were used. Physical characterization of these powders was done by measuring bulk, tapped, and true densities alongside scanning electron microscopy analysis. Flow properties were then calculated by the angle of repose, Hausner ratio, and Carr's compressibility index. Force, in-die thickness, and punch displacement data produced by the CS were captured during in-die compression. Compressibility was calculated using the Heckel equation. The physical characterization test results showed no significant difference between the two DTAs. Hardness results revealed that tablet formulations containing FlowLac® had higher sensitivity to an increase in compression force in comparison with StarLac®. From the Heckel plots generated by the CS during the compression cycle, yield pressure (Py) values were calculated for FlowLac®100 and StarLac®. The Heckel parameter (Py) for FlowLac®100 and StarLac® was calculated as 87.5 MPa and 85.2 MPa, respectively, during the compaction cycle at 5 kN. These data indicated that both powders are compressible and have brittle behavior. StarLac® is less brittle, which was shown by its lower sensitivity to compression force. Py values obtained from the Heckel equation described the plasticity of particles, which gives distinct information on the compressibility of both DTAs in real time during the compaction cycle.

Experimental test for mechanical properties of new tenon composite wall using thermal self-insulation block

Concrete hollow blocks have the advantages of simplified construction, reduced construction time, and better thermal performance, and can thereby achieve energy conservation in building engineering and significantly improved thermal and mechanical performance. A new tenon composite block is presented to achieve better self-thermal insulation and mechanical performance by integrating thermal materials into blocks. The tenon composite block application requires satisfying mechanical and seismic performance. Therefore, to prove the mechanical and seismic performance of the tenon composite block, a low cyclic loading test was performed on two self-thermal insulation wall specimens: the tenon composite block and the “Martha” block (used as the comparison specimen). The crack distributions, failure modes, force–displacement data expressed using hysteresis and skeleton curves, mechanical parameters of strengths, displacements, ductility coefficients, stiffness degradations, and equivalent viscous damping coefficients of the two specimens were analyzed in the low cyclic loading test. By analyzing the specimen crack distributions and failure modes, the tenon composite block was proven capable of effectively connecting the heat insulation and loading bearing parts. The differences in the force–displacement data and the mechanical parameters between the tenon composite block and “Martha” block specimens, such as the higher strength and stiffness of the tenon composite block specimen and similar ductility performance with the widely applied “Martha” specimen, were mainly caused by the size differences between the tenon composite block and “Martha” specimens. Finally, suggestions for tenon composite block applications are proposed to overcome the limitations of the tenon composite block’s ability to consume seismic energy.

Effect of Tempering on the Ductile-to-Brittle Transitional Behavior of Ni-Cr-Mo Low-Alloy Steel

About 10 years ago, super-high energy Charpy specimens at the National Institute of Standards and Technology were removed from inventory due to unacceptable variability in absorbed energy, leading to the advent of new methods and materials to reduce the variability and maintain the prescribed energy levels. In this paper, we investigated the ductile-to-brittle transitional behavior of Ni-Cr-Mo low-alloy steel by testing Charpy specimens with side-grooves as a function of the final temper temperature to define the processing conditions for these super-high energy levels. For each temper, absorbed energy and force-displacement data were measured as a function of test temperature; the former was used to assess transition temperature and upper-shelf energy and the latter was used to estimate shear fracture appearance (SFA). From the upper-shelf energy results, it was found that two of the temper conditions yielded energies in the super-high energy range and that side-grooves reduced the variability of the energy by preventing the formation of shear lips. From the SFA data, it was shown that the instrumented striker data and fractography were in excellent agreement, with the minor discrepancies attributed to difficulties with transitional fracture surfaces in the fractography and multiple crack arrest points in the instrumented striker data. In all, the data provided clear evidence that Ni-Cr-Mo low-alloy steel is a good solution for super-high energy Charpy indirect verification specimens.

Enhanced Biomechanical Performance of a Modern Polyester Surgical Mesh for Extensor Mechanism Reconstruction in Total Knee Arthroplasty

BackgroundExtensor mechanism (EM) disruption following total knee arthroplasty is a devastating postoperative complication. Reconstruction with a synthetic mesh is one treatment option, although the optimal mesh material remains unknown. This study sought to compare the mechanical properties of 2 mesh material types that can be used for EM reconstruction. MethodsMechanical properties of a polypropylene mesh (Marlex mesh) and Ligament Advanced Reinforcement System (LARS) mesh were compared using force-displacement data from a material testing machine simulating knee movement during normal human gait. Tension to failure/ultimate tensile load, stiffness coefficients, axial strain, and cyclic hysteresis testing were measured and calculated. ResultsCompared to polypropylene mesh, LARS mesh demonstrated a significantly higher mean ultimate tensile load (2223 N vs 1245 N, P = .002) and stiffness coefficient (255 N/mm vs 14 N/mm, P = .035) in tension to failure testing, and significantly more energy dissipation (hysteresis) in hysteresis testing (771 kJ vs 23 kJ; P ≤ .040). LARS mesh also demonstrated significantly less maximum displacement compared to the polypropylene mesh (9.2 mm vs 90.4 mm; P ≤ .001). ConclusionCompared to polypropylene mesh, LARS mesh showed superior performance related to force-displacement testing. The enhanced mechanical performance of LARS mesh may correlate clinically to fewer failures, increased longevity, and higher resistance to plastic deformation (extensor lag). Future research should evaluate survivorship and clinical outcomes of these meshes when used for EM reconstruction.

Billion degree of freedom granular dynamics simulation on commodity hardware via heterogeneous data-type representation

We discuss modeling, algorithmic, and software aspects that allow a simulation tool called Chrono::Granular to run billion-degree-of-freedom dynamics problems on commodity hardware, i.e., a workstation with one GPU. The ability to scale the solution to large problem sizes is traced back to an adimensionalization process combined with the use of mixed-precision data types that reduce memory pressure and improve arithmetic intensity, judicious use of the memory ecosystem on GPU cards as exposed by CUDA on Nvidia architectures, and a software implementation that prioritizes execution speed over modeling generality. The simulation approach is demonstrated for 3D scenarios with up to 710 million bodies for the frictionless case (of relevance in emulsions), and up to 210 million bodies for scenarios with friction (of relevance in terradynamics, additive manufacturing, soft-matter physics). The frictional contact model used draws on the Discrete Element Method (DEM). A performance benchmark shows linear scaling with problem size up to GPU memory capacity. The implementation has an application programming interface that enables it to interact in a cosimulation framework with third-party dynamics engines. This interaction is anchored by a force–displacement data exchange protocol that brings in external bodies as geometries defined by triangle meshes. We demonstrate the cosimulation mechanism by interfacing to an open source, multiphysics simulation engine called Chrono. Therein, triangular meshes define moving boundary conditions for Chrono::Granular, which in turn provides forces and torques acting on the triangular meshes. Several tests are considered for validation and scaling analysis purposes. The limiting aspects of the current implementation are its exclusive support of monodisperse granular systems, and its lack of handling geometries beyond spheres. These limitations are addressed by ongoing work.

Particle Compression Test: A Key Step towards Tailoring of Feedstock Powder for Cold Spraying

Cold spray is on the way to becoming a mainstream technology for coating and additive manufacturing processes. While there have been many advances in various aspects of this technology, the question of tailoring the ‘ideal’ feedstock powder for cold spraying has remained open. In particular, the mechanical strength and its dependence on the particle size, which are amongst the most relevant properties of the feedstock powder for cold spraying, are rarely covered when reporting powder specifications. This is mainly because of the lack of standardised methods of characterisation for these specific properties. In the present case study, we demonstrate how compression tests of single Inconel 718 particles by using a modified nanoindenter can address this central question. Data analyses are supported by finite element modelling of particle compression for a range of plastic behaviours. The results of simulation are then stored in the form of a surrogate model for subsequent comparison with the experimental data. Thus, the ultimate tensile strength and the size of the examined particles are calculated directly from the measured force-displacement data. The paper will also discuss how this information can be used to optimise cold spraying, and so, unveils a key step towards the design and manufacturing of cold-spray-specific feedstock powder.

Estimation of the hyperelastic parameters of fresh human oropharyngeal soft tissues using indentation testing

Patient-specific finite element (FE) modeling of the upper airway is an effective tool for accurate assessment of obstructive sleep apnea (OSA) syndrome. It is also useful for planning minimally invasive surgical procedures under severe OSA conditions. A major requirement of FE modeling is having reliable data characterizing the biomechanical properties of the upper airway tissues, particularly oropharyngeal soft tissue. While some data characterizing this tissue's linear elastic regime is available, reliable data characterizing its hyperelasticity is scarce. The aim of the current study is to estimate the hyperelastic mechanical properties of the oropharyngeal soft tissues, including the palatine tonsil, soft palate, uvula, and tongue base. Fresh tissue specimens of human oropharyngeal tissue were acquired from 13 OSA patients who underwent standard surgical procedures. Indentation testing was performed on the specimens to obtain their force–displacement data. To determine the specimens' hyperelastic parameters using these data, an inverse FE framework was utilized. In this work, the hyperelastic parameters corresponding to the commonly used Yeoh and 2nd order Ogden models were obtained. Both models captured the experimental force-displacement data of the tissue specimens reasonably accurately with mean errors of 11.65% or smaller. This study has provided estimates of the hyperelastic parameters of all upper airway soft tissues using fresh human tissue specimens for the first time.

Mechanical properties of starch esters at particle and compact level - Comparisons and exploration of the applicability of Hiestand's equation to predict tablet strength

Hydrophobic starch esters have potential as tablet matrix formers in controlled drug delivery. The mechanical properties of native starch (SN), starch acetate (SA) and starch propionate (SP) were studied at particle and compact level. Particle microhardness and modulus of elasticity were evaluated by nanoindentation. Force-displacement data of compressed powder were analyzed using Heckel in conjunction with piecewise regression, Kuentz-Leuenberger, Kawakita and Adams models, and yield pressure parameters were derived. Starches were characterized for chemical structure by Raman spectroscopy, crystallinity from powder x-ray diffraction (PXRD) patterns and surface energy from apparent contact angle measurements. A-type starch reflections were absent in the PXRDs of esters indicating greater amorphicity. Consequently, the particle microhardness of starch esters decreased leading to greater deformation during compaction and lower values of yield pressure parameters. These parameters increased with microhardness and ranked the starches in the order: SP < SA < SN. Fitting the experimental data into Hiestand's bonding index equation, a linear correlation (R2 = 0.902) was established between experimental and calculated tablet strength describing results of all starches, when Adams (το') yield pressure was used as the ‘effective compression pressure’ in the above equation.

Influence of compression at elevated temperature on the compactibility of thermo-mechanically processed polymers

Hot-melt extrusion (HME) is increasingly applied in the pharmaceutical industry for the formulation of solid dispersions of drugs with improved solubility and release. However, tableting of milled extrudates may present problems due to adverse thermo-mechanical effects on elasto-plasticity. In this work compression of hot-melt extruded polyvinyl based and polymethacrylate polymers with glass transition temperatures (Tg) up to 80 °C was performed at ambient (20 °C) and elevated (40 °C, ‘hot’ compression) temperature aiming for compactibility improvement. Polymers were characterized for morphology, particulate properties, thermal properties, microhardness and compaction behavior (‘in-die’ force-displacement data). Hot-melt extruded polymers showed lower Tg and work of compaction but higher elastic recovery and yield pressure (Kuenz-Leuenberger and Kawakita models) resulting in weak tablets. ‘In all cases, ‘hot’ compression decreased considerably the yield pressure for both unprocessed and extruded polymers indicating greater plasticity. For Eudragit® RSPO, Eudragit® L100-55 and Soluplus® with microhardness between 2.20 and 2.69 MPa it also increased consolidation due to softening of edges, thus facilitating interparticle slippage, which explained their tablet strength enhancement. Conversely, it did not affect the consolidation of Kollidon® SR with lower microhardness 0.31 and the large strength increase was attributed to the yield pressure reduction and the closeness of its Tg (42 °C) with the compression temperature increasing molecular mobility and operation of intermolecular forces. Compared to ambient compression, greater plastic deformation due to ‘hot’ compression was visible in the SEM images of tablet surfaces by the extensive formation of interparticle boundaries and by the elimination of pores. Relationships were found between yield pressure, elastic recovery, tensile strength and friability of tablets with homologous compression temperature which may be useful during formulation.

Identification of Pedicle Screw Pullout Load Paths for Osteoporotic Vertebrae

Study DesignA biomechanical study.PurposeTo determine the actual load path and compare pullout strengths as a function of screw size used in revision surgeries using postmortem human subject specimens.Overview of LiteraturePedicle screw fixation has become the standard of care in the surgical management of spinal instability. However, pullout failures are widely observed in osteoporotic spines and treated by revision surgeries using a higher diameter screw, performing cement augmentation, or increasing the levels of fixation. While the peak forces to final pullout are reported, the actual load path to achieve the final force level is not available. MethodsSix osteoporotic lumbar spines (L2–L5) were instrumented with 5.5×40 mm polyaxial screws and loaded along the axis of the screw using a material testing machine according to American Society for Testing of Materials 543-07 test protocol. Tests were again conducted by replacing them with 6.5×40 mm (group A) or 7.5×40 mm (group B) screws. Force-displacement data were grouped and load paths (mean±1 standard deviation) were compared.ResultsPullout strength decreased by 36% when the size of the revision screw was increased by 1 mm, while it increased by 35% when the size of the revision screw was increased by 2 mm compared to the index screw value. While the morphologies of the load paths were similar in all cases, they differ between the two groups: the larger screw responded with generally elevated stiffer path than the smaller screw, suggesting that revision surgery using a larger screw has more purchase along the inserted body-pedicle axis.ConclusionsA larger screw enhances strength and increases biomechanical stability in revision surgeries, although the final surgical decision is made by the clinician, which includes the patient’s anatomy and associated characteristics.

Rayleigh Damping Modelling to Assess Viscous Behaviour in Actuated Breast Tissue

Breast cancer is a significant health problem worldwide. Emerging non-invasive methods assess tumor presence by its impact on breast tissue mechanics. This paper outlines a method to identify equivalent viscous damping in breast tissue and fit a model based on the Rayleigh damping (RD) model. Surface motion information of actuated breast tissue was captured using the Digital Image Elasto Tomography (DIET) system. The viscous damping was calculated for over 14,000 reference points using an ellipse fitted to the force-displacement hysteresis loop response data to calculate work done. A damping model based on RD is suggested and fit to median filtered data of viscous damping constant plotted against the major ellipse axis. This successfully described the trend for all 29 breasts (14 cancerous, 15 healthy) with average R2 values ranging from 0.79-0.88. One model coefficient, ‘a’, proportional to local mass, showed reasonable consistency among the subjects and decreased with increasing frequency. No significant difference in this ‘a’ coefficient between healthy and cancerous breasts showed indication of diagnostic potential. However, consistent values across all breasts suggest it is a fundamental tissue property. Further suggestions to normalise the major axis by frequency demonstrate the potential for the model to be developed to describe viscous behaviour of breast tissue in the form of storage and loss modulus.

Experimental investigation of adhesive fillet size on barely visible impact damage in metallic honeycomb sandwich panels

Aluminum hexagonal honeycomb panels are commonly used in the aerospace industry to reduce weight due to their high stiffness to mass ratio. The panels are commonly involved in incidents where they are dented in the out-of-plane direction which causes plastic deformation in the face-sheet and buckling collapse of the thin repeating cell-walls in the core. This paper investigates the responses to barely-visible-impact-damage (BVID) in aluminum honeycomb sandwich panels in the out-of-plane direction with attention to the structural adhesive. The structural adhesive forms a fillet shape between the face-sheet and the aluminum core during the curing process and in some cases can encompass over 50% of the honeycomb core thickness. The adhesive fillets become stiff after curing and are able to brace the thin metallic cell-walls and prevent buckling in sections of the core enclosed in adhesive. It was shown that larger fillets cause the damage to occur deeper in the core. Force-displacement data collected from quasi-static experiments showed that as the amount of adhesive used in honeycomb panels was increased, the peak force required to produce a specified maximum dent depth increased as well. Absorbed energy positively correlated with an increasing quantity of adhesive; showing improvements of up to 50% when comparing panels with the largest amount of adhesive and no adhesive. This paper provides relationships between the quantity of adhesive used to fabricate metallic honeycomb sandwich panels and the damage resistance and energy absorption under BVID conditions.