Wall Failure Research Articles

The failure of partition walls resulted from excessive deflection of the prestressed ribbed floor slab

The failure of partition walls resulted from excessive deflection of the prestressed ribbed floor slab

Abdominal wall failure

Abdominal wall failure

Discrete macro - models of nonlinear interlocking mechanisms in the out-of-plane failure of masonry walls

AbstractHistorical unreinforced masonry (URM) constructions are generally vulnerable to out-of-plane (OOP) failures due to the absence of rigid floors and poor connections between orthogonal walls. That leads to the activation of rocking mechanisms of external walls, whose ultimate force and displacement are affected by complex nonlinear interactions with sidewalls. These interactions are often neglected in the engineering practice, potentially leading to significant approximations, as demonstrated by experimental and numerical studies available in the literature. As a novel contribution to the field, this paper presents an upgraded discrete macro-element model (DMEM) to predict the rocking capacity of OOP loaded URM walls interacting with sidewalls. Considering both the onset and the evolution of the rocking mechanism of the front wall, interlocking effects with the sidewalls are first simulated through frictional resistances using the macro-block model (MBM) and the nonlinear kinematic approach of limit analysis. Then, the upgraded DMEM is implemented on the basis of the equivalence between the continuous distribution of these forces, introduced as a further novelty of the paper, and the discrete distribution of lateral elastic-plastic links, accounting for mechanical and geometrical nonlinearities. The results of the two models are discussed in terms of both frictional resistance-displacement and pushover curves, referring to a case study of a front wall belonging to a two-storey URM building. The wall response is also compared with the results derived from the original source of the case study and analysed by changing the number of nonlinear links to define different levels of accuracy.

Cochlear implantation in otosclerosis: surgical and audiological outcomes between ossified and non-ossified cochlea.

To evaluate (1) Audiological and surgical outcomes in patients with otosclerosis following cochlear implantation. (2) surgical difficulties and outcomes between both groups. (3) Audiological outcomes between both groups. Retrospective study conducted at Otology and Skull Base Surgery Center. Data were analyzed from 111 patients with otosclerosis (114 ears) who underwent cochlear implant surgery using the cochlear implant database. Demographic characteristics (age, sex, and operated ear), auditory outcomes, and operative details (extent of cochlear ossification, surgical approach [posterior tympanotomy or subtotal petrosectomy], electrode insertion [partial/complete, scala tympani or vestibuli], and complications) were analyzed Auditory outcomes were assessed over at least one year follow-up period using pure tone audiometry and speech discrimination scores. Patients were divided into two groups (with and without cochlear ossification) to compare auditory outcomes and surgical outcomes. The mean age of patients with ossified and non-ossified cochlea was 60.04 and 62.22years respectively. Sixty-five of 114 ears had cochlear ossification, with complete round window involvement in 75.4% of these patients, while the rest had partial or complete basal turn ossification. Subtotal petrosectomy was performed in 63.1% and 28.6% of ossified and non-ossified cochlea respectively while the rest underwent cochlear implantation through posterior tympanotomy. Only one case had scala vestibuli insertion and four had incomplete electrode insertion. Six patients underwent re-implantation due to infection, device failure, and erosion of the posterior canal wall. Auditory outcomes among patients with ossified otosclerosis were slightly better than those without ossification but this difference was not statistically significant. Cochlear implantation for otosclerosis yields excellent auditory outcomes with a low rate of surgical complications, despite the high incidence of cochlear ossification.

Influence of ore-drawing port position on ore-rock flow characteristics in ore pass and lateral pressure on ore pass wall

The blockage and the deformation and failure of the ore pass walls constitute two major problems in applying the ore passes in mines. These problems, which affect the normal operation of mine production, have attracted widespread attention worldwide. The labeled-particle layers method based on numerical simulation was used to investigate the flow characteristics of the ore-rock bulk in the ore pass under different eccentric distances of the ore-drawing port center and ore pass centerline. Moreover, the overpressure coefficient and overpressure number are used to evaluate the degree of damage to the ore-pass wall. The results show that: (1) During the ore drawing process under different eccentricities, the flow patterns of the topmost labeled-particle layers in the ore pass are always in a “—” shaped distribution, and the other layers in the ore pass gradually transition from a “—” shape to a “U” shaped distribution, and then gradually to a “V” shape closer to the drawing funnel; (2) in the range of the ore-drawing funnel, the flow pattern of the ore-rock bulk gradually changes from an upright “V” shape to an italic “V” shape with increasing eccentricity and tip slants to the drawing port, and is less affected in the shaft; and (3) the dynamic lateral pressure caused by the ore-rock flow mainly acts on the lower part of the storage section. When the eccentricity is 0.5 m, the maximum overpressure coefficient and overpressure times are the smallest, leading to the lowest damage degree of the ore pass wall.

Investigating the simulation test and acoustic emission characteristics of structural-control type rockbursts in deep underground environments

Deep underground projects are in a complex in-situ stress environment, and rock burst disasters induced by the hard and brittle failure of the rock mass are prone to occur around the tunnel openings. In this study, we aim to investigate the impacts of geological weak surfaces in rock masses on rockbursts and the spatiotemporal evolution of microcracks during the development of rockbursts. To achieve this objective, two sets of cubic specimens containing a circular through-hole were designed. One set of specimens had prefabricated unfilled cracks around the openings. Subsequently, the rockburst development process within the deep tunnel was replicated by subjecting both groups of specimens to identical gradient loading using a true triaxial test system. During the test, a micro camera was used to record the failure of the borehole wall in real-time, and an acoustic emission monitoring system was utilized to capture the stress waves released during structural damage. Finally, a multi-level synergistic analysis of the rockburst damage mechanism was carried out based on the macro-imaging data and micro-acoustic emission data. The results show that failure in high-stress environments within tunnels mainly includes microcrack initiation, particle ejection, crack propagation, local cracking, slabbing spalling, damage penetration, and rockburst damage. The time–frequency domain information of acoustic emission signals is highly perceptive and representative of the structural damage state of the specimens. The mutation characteristics observed in time-domain parameters, such as acoustic emission amplitude, event rate, ringing, and cumulative energy, correspond to drastic alterations in the internal structure of the rock. The distribution characteristics of frequency-domain parameters, such as acoustic emission peak frequency, dominant frequency energy, and frequency centroid, reflect different crack scales and damage modes. The diffusion of frequency centroid indicates that the damage and failure patterns within the rock are evolving towards a more complex direction. The energy magnitude of acoustic emissions represents the damage intensity during the development of rockburst. The root causes of induced structural-control type rockbursts in deep hard brittle rock masses are the combined effects of localized high-stress concentrations and large-scale discontinuous geological structures, such as natural joints, fissures, and structural planes. The naturally occurring large-scale through-type geological weak surfaces within the rock mass reduce the strength of the surrounding rock, alter the location of stress concentration, and change the initial damage characteristics. Moreover, they promote the evolution of rockbursts, thereby increasing their destructive intensity.

Flexural behavior and design of aluminum alloy portal frame eaves joints

Aluminum alloy portal frames (AAPFs) are suitable for both long-term and temporary buildings owing to their light weight, ease of installation and disassembly, and excellent corrosion resistance. Due to the critical importance of joint mechanical behavior for structural safety, this paper conducted experimental and numerical studies on the flexural behavior of AAPF eaves joints. Initially, bending tests on four AAPF eaves joints revealed three failure patterns: connection plate, column, and hole wall failure. The failure patterns are determined by the weakest of these three components. Adding haunches increased the bending zone area, thereby increasing the ultimate bearing capacity by 110 % compared to joints without haunches. Furthermore, strain curves indicated that the load transfer zone was subjected to a bending-shear force state, consistent with the principle that the bolt group shear forms a force couple to transfer the moment. Subsequently, a finite element (FE) model was developed and validated to provide a foundation for subsequent parametric studies and theoretical analysis. The parametric analysis considers bolt diameter, connection plate thickness, aluminum alloy web thickness, and bolt end distance. The bearing capacity corresponding to three failure patterns was discussed, and a design method for the flexural bearing capacity was proposed. The design method for stiffness model was also proposed based on the component-method and parametric analysis. Finally, this paper presented and validated the design steps for the flexural behavior of the eaves joints throughout the whole process, providing an important reference for engineering design.

Numerical analysis of duct wall failure in a prototype FAIDUS design-based generation IV SFR fuel subassembly under flow blockage accident

An ingenious prototype Fuel Assembly Inner DUct Structure (FAIDUS) design is conceptualized under the Generation IV safety philosophy to prevent large-scale corium pool formation following total coolant flow blockage accident. The early failure of the duct wall provides a built-in guideway for molten material relocation out of the core region, ensuring inherent safety robustness. Therefore, understanding the duct wall failure mechanism is critical for evaluating accident mitigation potential of the FAIDUS design. In this regard, a transient enthalpy-based multiphase computational model is developed to investigate the heat transfer and fluid flow behavior involved during the duct wall failure in 3-D domain. The numerical model is employed initially to simulate wall failure in the EAGLE ID1 in-pile test. The model results are validated against the in-pile test data. Subsequently, FAIDUS duct wall failure in a prototype fast reactor fuel subassembly (SA) is investigated employing the present model. The study reveals that the large heat flux from the molten pool to the duct is the main reason for the duct wall failure. The duct failure starts with an initial rupture across the corners of the hexagonal-shaped duct and progresses to total failure of the duct wall by the expansion of the rupture over the whole duct wall area with time. The outer hexcan wall sustains only minor thermal damage during the duct wall failure process. The present study explores the associated thermal-hydraulics, molten pool dynamics, crust formation behavior, and event sequences involved in duct wall failure in great detail. The simulation findings suggest that the FAIDUS SA design facilitates premature failure of the slim duct wall prior to the hexcan wall failure. This could potentially enable early discharge of the molten corium away from the core region, limiting the accident progress.

In Vivo Quantification of Ascending Thoracic Aortic Aneurysm Wall Stretch Using MRI: Relationship to Repair Threshold Diameter and Ex Vivo Wall Failure Behavior.

Ascending thoracic aortic aneurysms (aTAAs) can lead to life-threatening dissection and rupture. Recent studies have highlighted aTAA mechanical properties as relevant factors associated with progression. The aim of this study was to quantify in vivo aortic wall stretch in healthy participants and aTAA patients using displacement encoding with stimulated echoes (DENSE) magnetic resonance imaging. Moreover, aTAA wall stretch between surgical and nonsurgical patients was investigated. Finally, DENSE measurements were compared to reference-standard mechanical testing on aTAA specimens from surgical repairs. In total, 18 subjects were recruited, six healthy participants and 12 aTAA patients, for this prospective study. Electrocardiogram-gated DENSE imaging was performed to measure systole-diastole wall stretch, as well as the ratio of aTAA stretch to unaffected descending thoracic aorta stretch. Free-breathing and breath-hold DENSE protocols were used. Uniaxial tensile testing-measured indices were correlated to DENSE measurements in five harvested specimens. in vivo aortic wall stretch was significantly lower in aTAA compared to healthy subjects (1.75±1.44% versus 5.28±1.92%, respectively, P = 0.0004). There was no correlation between stretch and maximum aTAA diameter (P = 0.56). The ratio of aTAA to unaffected thoracic aorta wall stretch was significantly lower in surgical candidates compared to nonsurgical candidates (0.993±0.011 versus 1.017±0.016, respectively, P = 0.0442). Finally, in vivo aTAA wall stretch correlated to wall failure stress and peak modulus of the intima (P = 0.017 and P = 0.034, respectively), while the stretch ratio correlated to whole-wall thickness failure stretch and stress (P = 0.013 and P = 0.040, respectively). Aortic DENSE has the potential to assess differences in aTAA mechanical properties and progressions.

Tensile testing in feline ventral abdominal coeliotomy closure with different sizes of polydioxanone suture material: a biomechanical study.

The aim of this study was to evaluate, in vitro, the load and type of failure of the sutured ventral abdominal fascia of cats with different sizes of suture material made of polydioxanone (PDX) (2-0, 3-0, 4-0, 5-0 USP). A total of 32 samples of the ventral abdominal wall from 16 cadaveric cats were harvested using an hourglass-shaped template. The samples were sectioned longitudinally along the linea alba and then sutured together in a continuous pattern using four different randomly assigned sizes of pdx suture material (2-0, 3-0, 4-0, 5-0 USP). A universal testing machine was used for linear distraction of the samples. The tensile strength and type of failure were recorded and analysed. Three types of failure were defined: suture material failure (S), suture line failure (T1) and failure of the abdominal wall further away from the linea alba (T2). The frequency of suture material failure decreased with increasing suture size. Suture size 5-0 failed due to a S failure in 6/8 samples, PDX 4-0 failed in 2/8 samples and PDX 3-0 failed in only 1/8 samples. However, PDX 2-0 failed due to only T1 or T2 failures, with both failures being almost equally represented. No statistically significant differences in the load to failure between PDX 2-0, 3-0 and 4-0 were noted (P >0.05). The risk of suture failure increased with decreasing suture size diameter. PDX 2-0 and 3-0 can be used without reservation for the closure of ventral midline coeliotomy in cats. Although there was no statistically significant difference between PDX 2-0, 3-0 and 4-0, PDX 4-0 showed a higher probability for suture breakage and should be used only after careful consideration of the patient while clinical evaluation is pending. Pdx 5-0 cannot be recommended as a safe suture size for this type of surgical closure.

Investigation of Type A Aortic Dissection Using Computational Modelling.

Aortic dissection is a catastrophic failure of the endothelial wall that could lead to malperfusion or rupture. Computational modelling tools may help detect arterial damage. Technological advancements have led to more sophisticated forms of modelling being made available to low-grade computers. These devices can create 3D models with clinical data, where the clinical blood pressure waveforms' model can be used to form boundary conditions for assessing hemodynamic parameters, modelling blood flow propagation along the aorta to predict the development of cardiovascular disease. This study presents patient-specific data for a rare case of severe Type A aortic dissection. CT scan images were taken nine months apart, consisting of the artery both before and after dissection. The results for the pre-dissection CT showed that the pressure waveform at the ascending aorta was higher, and the systolic pressure was lagging at the descending aorta. For the post-dissection analysis, we observed the same outcome; however, the amplitude for the waveform (systolic pressure) at the ascending aorta increased in the false lumen by 25% compared to the true lumen by 3%. Also, the waveform peak (systolic) was leading by 0.01 s. The hemodynamic parameter of wall shear stress (WSS) predicted the aneurysm's existence at the ascending aorta, as well as potential aortic dissection. The high WSS contours were located at the tear location at the peak blood flow of 0.14 s, which shows the potential of this tool for earlier diagnosis of aortic dissection.

Sliding Shear Failure of Basement-Clamped Reinforced Concrete Shear Walls.

After an earthquake struck Chile in 1985, sliding shear failure was observed in the clamping zone of stabilising walls. Even houses with only four storeys can fail due to sliding shear below basement ceilings. This type of failure has received little attention in the past; however, it leads to premature failure of the clamping effect in the basement box. Bending deformations cannot fully develop, which significantly reduces the seismic safety; it is thus important to learn more about the sliding shear failure of basement-clamped shear walls. The overall behaviour is analysed based on three large-scale shear wall tests. The deformation states around the sliding shear zone are evaluated and a simple estimate is given of when sliding shear failure can occur.

Research on coal wall failure and stability control technology of large coal seams with a soft and thick seam

AbstractTo address the issues of coal rib instability and high occurrence of roof falls in high extraction height fully mechanized coal mining of soft coal seams, this study comprehensively employs theoretical analysis, numerical calculations, and field industrial experiments. By analyzing the distribution characteristics of coal rib displacement and deformation instability zones under different mechanical parameters of soft coal seams, the instability mechanism of coal ribs in high extraction height mining of thick and soft coal seams is revealed, and corresponding stability control techniques for high extraction height coal ribs and supports are developed. The study shows that the stability of coal ribs in high extraction height mining fields of soft and thick coal seams decreases as the values of mechanical parameters decrease. In other words, the smaller the cohesion and deformation parameters of the coal body, the more prone the coal rib is to roof falls. By utilizing advanced deep‐hole static water infusion technology, the frequency of roof falls in extremely soft high extraction height working faces is reduced by 80%, the average depth of roof falls is decreased by 35%, and the average length of roof falls is reduced by 50%. The stability of the coal ribs is effectively improved.

Experimental investigation of traditional Kath-Kuni wall system and traditional joints

In the Indian Himalayan region, the traditional vernacular construction system is a centuries-old system that is considered a seismic-resistant construction system. This practice is developed in the area over a period of time by the local communities and is never conventionally engineered. Hence, it is important to know about the behaviour of traditional construction systems and key features associated, under gravitational and lateral loading conditions. In the present research, experimental studies have been done on the full scale as well as scaled-down kath-kuni wall specimens, under push-over loading conditions, to characterize its overall behaviour, deformation and earthquake-resisting features. The failure of the kath-kuni wall was governed by friction capacity reduction followed by internal rotation in wooden layers. The kath-kuni system showed high ductile behaviour and the behaviour factor R was calculated as more than 5.4, and was compared with conventional brick masonry. The joints in the kath-kuni wall system have been identified and separate experimental studies, with varying member sizes, have been conducted to find out behaviour and capacity of these traditional joints upon loading. Analytical equations, to calculate capacity, have been proposed and compared with experimental results. The coefficient of friction was found to be varying in between 0.42–0.8 for different surfaces under constant overburden.

Enhanced elastic stability of a topologically disordered crystalline metal–organic framework

By virtue of their open network structures and low densities, metal–organic frameworks (MOFs) are soft materials that exhibit elastic instabilities at low applied stresses. The conventional strategy for improving elastic stability is to increase the connectivity of the underlying MOF network, which necessarily increases the material density and reduces the porosity. Here we demonstrate an alternative paradigm, whereby elastic stability is enhanced in a MOF with an aperiodic network topology. We use a combination of variable-pressure single-crystal X-ray diffraction measurements and coarse-grained lattice-dynamical calculations to interrogate the high-pressure behaviour of the topologically aperiodic system TRUMOF-1, which we compare against that of its ordered congener MOF-5. We show that the topology of the former quenches the elastic instability responsible for pressure-induced framework collapse in the latter, much as irregularity in the shapes and sizes of stones acts to prevent cooperative mechanical failure in drystone walls. Our results establish aperiodicity as a counter-intuitive design motif in engineering the mechanical properties of framework structures that is relevant to MOFs and larger-scale architectures alike.

Design and additive manufacturing of bionic hybrid structure inspired by cuttlebone to achieve superior mechanical properties and shape memory function

Lightweight porous materials with high load-bearing, damage tolerance and energy absorption (EA) as well as intelligence of shape recovery after material deformation are beneficial and critical for many applications, e.g. aerospace, automobiles, electronics, etc. Cuttlebone produced in the cuttlefish has evolved vertical walls with the optimal corrugation gradient, enabling stress homogenization, significant load bearing, and damage tolerance to protect the organism from high external pressures in the deep sea. This work illustrated that the complex hybrid wave shape in cuttlebone walls, becoming more tortuous from bottom to top, creates a lightweight, load-bearing structure with progressive failure. By mimicking the cuttlebone, a novel bionic hybrid structure (BHS) was proposed, and as a comparison, a regular corrugated structure and a straight wall structure were designed. Three types of designed structures have been successfully manufactured by laser powder bed fusion (LPBF) with NiTi powder. The LPBF-processed BHS exhibited a total porosity of 0.042% and a good dimensional accuracy with a peak deviation of 17.4 μm. Microstructural analysis indicated that the LPBF-processed BHS had a strong (001) crystallographic orientation and an average size of 9.85 μm. Mechanical analysis revealed the LPBF-processed BHS could withstand over 25 000 times its weight without significant deformation and had the highest specific EA value (5.32 J·g−1) due to the absence of stress concentration and progressive wall failure during compression. Cyclic compression testing showed that LPBF-processed BHS possessed superior viscoelastic and elasticity energy dissipation capacity. Importantly, the uniform reversible phase transition from martensite to austenite in the walls enables the structure to largely recover its pre-deformation shape when heated (over 99% recovery rate). These design strategies can serve as valuable references for the development of intelligent components that possess high mechanical efficiency and shape memory capabilities.

Friction stir seam- and spot-welded aluminium honeycombs: Enhanced structural integrity eliminating adhesive bonding challenges

Aluminium honeycombs serve as a primary core material for energy absorption in various transportation and structural applications, with particular emphasis on their superior strength in the out-of-plane direction. However, conventional fabrication methods rely on adhesive bonding of aluminium strips, revealing poor bond strength under collapse stress. Premature structural failure arises from adhesive failure and subsequent debonding of cell walls, occurring before the aluminium strips fail. Addressing this, an innovative approach utilizing friction stir seam, and spot welding has been introduced to overcome adhesive bonding limitations. Welded joints exhibit a remarkable tenfold increase in strength compared to adhesive bonds. Notably, welded honeycombs demonstrate 32–37% higher crushing strength and an 80–84% increase in specific energy absorption capacity over adhesive-bonded variants. Collapse mechanisms involve pure buckling in seam-welded honeycombs without weld region failure, while spot-welded honeycombs display a combination of bending-shear and spot tearing, particularly evident with wider weld spacing. Obtaining longitudinal loading on seam-welded honeycomb walls is advantageous because of its 57% higher normalized maximum load capacity compared to the shear-tensile strength obtained for spot-welded walls. This study marks a significant advancement in the existing manufacturing route for honeycombs in achieving superior crushing performance.

TRM strengthening as effective prevention against premature failure of masonry walls

Masonry structures are very prone to cracking and premature failure in the presence of shear loading. Therefore, effective prevention of their premature damage is needed. This paper presents laboratory tests of small models made of autoclaved aerated concrete (AAC) blocks, which were externally reinforced using two different strengthening sets consisting of mortar and mesh, and subjected to diagonal compression. The experiments used a commercialised system designed for the strengthening of typical masonry substrates (brick, stone) and a low-cost and lowstrength mesh and mortar set used as part of a system for insulating buildings. The analyses presented are of a comparative nature and describe changes in the behaviour of the models depending on the strengthening set used. The application of full-surface strengthening clearly changed the behaviour of AAC walls from brittle one to the ‘pseudo-ductile’ one observed after the appearance of the first cracks. In all strengthened models, a significant increase in the load capacity (from 3% to 62%) and a post-peak phase were reported. An interesting finding was the high efficiency of nonstructural materials (plastering system), comparable to the effects of the use of commercialised system solutions. This strengthening can be successfully considered as an effective preventive action. Finally, a simplified method is provided to calculate the contribution of the strengthening to the load bearing capacity of the strengthened models. The method defines the effect of the mesh and the mortar independently, based only on the basic material properties of these two components.

Dynamic behavior of axially loaded masonry walls strengthened with different innovative techniques under explosion loading

In the realm of construction engineering, brick masonry stands out as a pivotal structural element, renowned for its widespread application. Given the load-bearing nature of masonry structures, the ramifications of wall failure under extreme loads induced by explosions are profound. Particularly concerning is the out-of-plane failure of walls, which occurs without warning and affords scant time for assessment of their response. Brick masonry, characterized by its brittleness and susceptibility to cracking, presents inherent challenges in this regard. Recent examples, such as the Beirut explosion in 2020 and the Nashville bombing in 2020, vividly illustrate the devastating consequences of inadequate blast resistance in masonry structures. These incidents serve as poignant reminders of the imperative to fortify masonry constructions against explosive threats. While ample research exists on the behavior of free-standing braced and unbraced masonry walls subjected to explosive loading, there remains a notable gap in understanding the response of strengthened masonry walls exposed to blast loading, especially when carrying varying axial loads. This study addresses this gap by investigating different strengthening methodologies, namely (1) Cement-mortar plaster, (2) Ferro-cement, and (3) Carbon Fiber-Reinforced Polymer (CFRP) laminate, aimed at enhancing the anti-blast performance of unreinforced masonry walls. The experimentation focuses on a specific unreinforced masonry wall measuring 5000 × 2800 × 230 mm3, constructed from clay bricks and subjected to axial compressive loads of 51, 30, and 9kN/m, corresponding to the loads on the 1st, 2nd, and 3rd storey walls of a 3-storey masonry building, respectively. Utilizing a sophisticated finite-elements code, Abaqus, equipped with an explicit module and Concrete Damage Plasticity model, the blast simulations are meticulously conducted. The walls are meticulously modeled through detailed micro-modeling techniques. Results showed that the utilization of CFRP on the explosion-facing surface of the wall resulted in a remarkable reduction in damage, with the highest decrease of 64% achieved under the lowest axial compression. Conversely, the minimum decrease of 61.71% was recorded under maximum axial compression, highlighting the efficacy of CFRP in mitigating damage caused by explosions on walls. This research sheds light on effective methods to enhance the blast resistance of masonry walls, offering valuable insights for improving structural resilience and informing building codes. Its findings are crucial for ensuring the safety and security of infrastructure against explosive threats, ultimately safeguarding lives and property.

Concurrent geometrico-topological tuning of nanoengineered auxetic lattices fabricated by material extrusion for enhancing multifunctionality: Multiscale experiments, finite element modeling and data-driven prediction

This study demonstrates the multifunctional performance of innovative 2D auxetic lattices through a combination of multiscale experiments, finite element modeling and data-driven prediction. A geometric modeling approach utilizing Voronoi partitioning and a unique branch-stem-branch (BSB) structure, patterned according to 2D wallpaper symmetries, enables precise concurrent geometric and topological tuning of lattices across a continuous parameter space. Selected architectures are physically realized via material extrusion of polylactic acid (PLA) infused with carbon black (CB). Experimental characterizations, supported by Finite Element modeling, reveal the significant influence of BSB structure's design parameters on mechanical and piezoresistive performance under tensile loading, with a remarkable Poisson’s ratio of -0.74, accompanied by a 15-fold increase in elastic stiffness and a 34-fold increase in strain sensitivity. Additionally, architecturally, and topologically tailored lattice structures exhibit tunable damage sensitivity, reflecting the rate of conductive network destruction within the lattice. This offers insights into the rapidity of cell wall failure, with a steeper slope of the piezoresistance curve in the inelastic regime indicating a faster breakdown and quicker onset of mechanical failure. Integration of Gaussian Process Regression enables accurate exploration of the design space beyond realized structures, highlighting the potential of these intelligent lattice structures for applications such as sensors and in situ health monitoring, marking a significant advancement in multifunctional materials.