Quasi-static Compressive Loading Research Articles

Mechanical properties of 3D continuous CFRP composite graded auxetic structures

A novel type of petal-like linear/linear symmetrical gradient auxetic structures with multi-stage deformation ability was designed and fabricated by using lightweight and high strength continuous carbon fiber reinforced composites to avoid the cliff-like stress drops caused by fiber fractures. The mechanical response, deformation mode and energy absorption capacity of the structures under quasi-static compression and low-speed impact loads were investigated by using finite element method in combination with experiments. The outcomes revealed that, through appropriate structural design, these auxetic structures made from fiber reinforced composites could also exhibit a stress plateau stage. Moreover, the gradient design enhanced the equivalent compression modulus of structures formed with smaller angles, while concurrently suppressing the buckling failure in structures with larger angles, thereby facilitating the predictability of structural failure. Besides, in comparison to traditional multicellular structures, the composite gradient petal-like structures exhibit superior energy absorption characteristics, thus rendering them promising candidates for applications in the construction, marine, and wind power industries.

Mechanical properties and failure behavior of additively manufactured Al2O3 lattice structures infiltrated with phenol-formaldehyde resin

The lightweight design and load-bearing capacity of underwater vehicles remain perennial focal points. Ceramic lattice structures (CLSs) offer significant weight reduction while maximizing structural strength; however, their inherent brittleness poses a limitation. To optimize the performance of CLSs for underwater vehicle applications, a biomimetic Al2O3/phenol-formaldehyde (PF) resin composite structure (APCS) was proposed and fabricated by infiltrating additive-manufactured Al2O3 lattice structures (ALSs) with PF. Comprehensive assessments of the quasi-static mechanical properties were conducted using both experimental and simulation methods. The specific compressive strength and specific energy absorption of the APCSs under quasi-static compressive loading exhibited remarkable improvements, with the maximum values achieved from the body-centered cubic (BCC)/PF structure increasing by ∼15.23 and ∼307.93 times, respectively. In contrast to ALSs, the failure process of APCSs was gradual, with the confining pressure introduced by the PF promoting transverse crack propagation and layer-by-layer failure, thereby strengthening the ceramic lattice. Toughing mechanisms (i.e., crack arrest, crack deflection, and branching) were also observed in the APCSs. Furthermore, the simulation results aligned well with the experimental results, providing an in-depth analysis of internal damage and crack propagation. The improvements introduced by the composite structure in this study provide a reliable approach for obtaining lightweight and strong materials, thereby accelerating the application of ceramic-based materials in underwater vehicles.

The mechanical responses of SiC-coated carbon-bonded carbon fiber composites under quasi-static cyclic compressive loading

SiC-coated carbon-bonded carbon fiber composites (CBCFs), serving as novel thermal protection materials for hypersonic vehicles, are manufactured to investigate their mechanical properties concerning reusability. Comprehensive analyses are performed on their microstructures, including the fiber arrangement and the morphology of individual fibers and interconnecting bonds. The results demonstrate that SiC-coated CBCFs exhibit higher elastic moduli and strengths in both typical directions compared to bare CBCFs. To evaluate their durability in repeated use scenarios, a series of quasi-static uniaxial cyclic compressive experiments are conducted with emphasis on the variations of deformation recovery, load bearing and energy dissipation. The results indicate that SiC-coated CBCFs exhibit stable deformation recovery ability in the OP direction after the 25th cycle, with a decelerating decline in their load-bearing capacity observed over subsequent cycles. The energy loss coefficient initially decreases with increasing cycle number, and higher compression loads enlarge the amount of energy that is dissipated in the first cycle. These insights elucidate critical correlations between the mechanical properties of SiC-coated CBCFs and the number of compressive cycles, contributing to the optimization of their practical utilization in reusable scenarios.

Energy absorption characteristics of modular assembly structures under quasi-static compression load

Inspired by the assembly of building blocks, an innovative modular assembly structure (MAS) is proposed. With its modular design and versatility, MAS can be tailored to diverse working environments and task requirements. A prototype MAS is generated through three-dimensional (3D) printing, and subsequent compression tests consistently display energy absorption performance akin to a finite element model, affirming the validity of the simulations. Multiple MASs are obtained through the assembly of oblique cross cells, and the effect of compression direction on the energy absorption capacity of MASs is discussed. It is found that transverse compression outperforms longitudinal compression in energy absorption, and MAS with four cells and transverse loading demonstrates the highest specific energy absorption (SEA) value. Furthermore, quadrilateral, pentagonal, and hexagonal cells are proposed to obtain more MASs, and the compression performance of these MASs is evaluated by varying the frame structure thickness d and supporting structure thickness j of cells. Results highlight the superior energy absorption efficiency of the pentagonal element structure. Notably, parameter d has a more pronounced impact on energy absorption compared with parameter j. When j is 2.0 mm and d increases from 1.0 mm to 2.0 mm, the SEA values of quadrilateral, pentagonal, and hexagonal MASs increase by 113.70, 139.45, and 86.25 J/kg. In summary, MASs exhibit impressive energy absorption capabilities, promising versatile applications in energy absorption and anti-collision mechanisms across various scenarios.

Quasi-static uniaxial compression and low-velocity impact properties of composite auxetic CorTube structure

Auxetic structures are gaining great attention due to their unique contraction deformation characteristics under compression and impact. In this paper, high performance carbon fiber-reinforced composites are used to fabricate the auxetic structure consist of corrugated sheets and tubes (CorTube). The quasi-static uniaxial compression and low-velocity impact properties of composite CorTube structure are explored. The response of the composite CorTube structures under quasi-static compression loads are analyze through a combination of theoretical analysis, simulations, and experimental tests. Additionally, drop-weight impact tests are conducted using a rigid impactor with a hemispherical head to examine the effects of impact energy levels, impact locations, and corrugated sheet thickness on the impact response of CorTube structure. Enhancing corrugated sheet-tube bonding via modified cross members and reducing tube crushing during quasi-static compression are notable findings. The results also highlight the remarkable auxetic properties of the composite CorTube under low-speed impact, and the impact resistance could be enhanced by increasing the corrugated sheet thickness and stiffness. Various failure modes were observed, including cracks, pits, tube crushing, and delamination. Significantly, peak-impacted specimens exhibited greater maximum displacement with lower peak impact forces. This study offers insights into the deformation and failure modes of auxetic CorTube structures under low-velocity impact.

Development of predictive model for compressive strength of eco-brick masonry walls using numerical method

The usage of waste plastics in the form of eco-bricks for the construction of buildings is gradually gaining traction. However, the performance of eco-brick masonry walls is not sufficiently known, and the process of setting up experimental rigs for the conduct of compressive strength test of masonry are usually cumbersome and expensive. This study investigated the compressive strength performance of eco-brick masonry walls and developed a predictive model for evaluating the strength of eco-brick masonry walls. Waste polyethylene terephthalate (PET) bottles were physically recycled and utilised to manufacture four samples of eco-bricks, strength grades 40.5, 21.02, 13.52 and 3.05 N/mm2 using stone dust, sharp sand and laterite at predetermined moisture contents. The eco-bricks were laid with seven grades of mortar to build 54 eco-brick masonry prisms. A quasi-static compressive loading test was carried out on the masonries, and predictive models were developed using multiple non-linear regression. The study found that eco-brick masonry prisms supported large loads and failed due to the propagation of tensile cracks and debonding of the units. The study also found that the compressive strength of eco-brick masonry is a power function of the compressive strength of eco-bricks and the mortar used for the bonding. It was determined that the mean ratio of the expected to experimental prism strength was 1.002. The mathematical model developed in this study for predicting the strength of eco-brick masonries can significantly evaluate the compressive strength of eco-brick masonry.

Discharge and ignition mechanism of high-entropy alloy induced by crack propagation under quasi-static compressive load

In order to reveal the discharge and ignition mechanism of high-entropy alloy under quasi-static compression load, the stress, potential and ignition evolution process of high-entropy alloy with prefabricated cracks were tested. The atomic structure and dislocation evolution of high-entropy alloy during crack propagation and compression were determined by molecular dynamics simulation, and the discharge mechanism of crack tip was analyzed at the micro level. Based on the calculation of Gibbs free energy, the products in the ignition reaction process were predicted. The results of mechanical/thermal/electrical characteristics induced by compressive load show that the discharge usually occurs near the ignition moment of specimen fracture, and the maximum potential signal can reach 34.2 V. The formation of crack group, crack propagation, local stress concentration, charge accumulation and release at the crack tip jointly induce the generation of discharge signals. With the propagation of cracks, a large number of stacking faults appear and a diamond-shaped failure zone is formed. The increase of disordered atoms leads to fracture. During the compression process, a large number of dislocations induce the separation of charges, which aggravates the discharge at the crack tip. In the Hf-Zr-Ti-Ta-Nb-Cu high-entropy alloy system, the reaction product Ta2O5 is preferentially generated, while in the Ti–Zr-Hf-Cu system, Ti2O3 is preferentially generated. The tip discharge and chemical bond fracture during crack propagation induce ignition, and the chemical bond recombines with energy release.

Enhancing crashworthiness characteristics of modified hexagonal honeycomb structural panels through stretching and bending of ribs

The effects of stretching and bending of concave, convex, and horizontal ribs on the energy absorption characteristics of modified hexagonal honeycomb structural panels are investigated under in-plane quasi-static compression loading conditions. In this regard, five hierarchical modified structural panel configurations were fabricated using polylactic acid material (PLA) via a fused filament 3D printer, ensuring uniform wall thickness in the 1.5–2 mm range. The panels included the regular hexagonal panel (RHP), regular hexagonal panel with concave rib (RHCP), regular hexagonal panel with convex rib (RHXP), regular hexagonal panel with concave and horizontal ribs (RHCRP), and regular hexagonal panel with convex and horizontal ribs (RHXRP). In-plane quasi-static compressive loading tests were conducted to analyze crush resistance characteristics, and buckling modes of the modified honeycomb panels were examined through experimental and finite element analysis procedures. The result indicates that the specific energy absorption capacity (SEA) of RHXRP is increasing significantly compared to the SEA capacity of other categories of the structures. The changes in failure modes and increased crush energy absorption characteristics of modified RHP with the introduction of concave, convex, and horizontal ribs are elaborated.

Auxetic lattice structures consisting of an enhanced trigram frame unit cell with superior stiffness

Superior stiffness is deemed essential for structures intended for several applications. The stiffness enhancement can be achieved by adopting structures that deform based on the stretching-dominated mechanism instead of the bending-dominated mechanism. This paper proposes a novel auxetic unit cell design and two distinct lattice structures dominated by stretching when subjected to quasi-static compressive and tensile loadings. The structures are manufactured via the fused deposition modeling (FDM) 3D printing method with the use of polylactic acid (PLA) filament as the patent material. The investigation also includes theoretical analyses and finite element (FE) simulations, all yielding consistent results. Response Surface Methodology (RSM) is also employed to understand the influence of three geometric parameters. Besides, single-objective optimization is conducted to maximize the stiffness through geometry design, and multi-objective approaches are implemented to improve the stiffness while simultaneously reducing relative density. Finally, different unit cells, which deform based on the stretching-dominated mechanism, are selected to represent their respective classifications, enabling a comparison of their potential stiffness capacity with the designed structures in this study. Remarkably, it is highlighted that the proposed unit cells and structures outperform others in terms of specific stiffness, making them a promising choice for use in structural engineering.

Mesoscopic mechanical study on quasi-static compression of coral aggregate seawater concrete after high temperature exposure

Coral aggregate seawater concrete (CASC) is a pioneering concrete made by blending and curing coral reefs, coral sands, cement, mineral admixtures, chemical additives, and seawater. The investigation of its mechanical properties is important for both theoretical and engineering purposes. This paper aims to investigate the quasi-static mechanical properties of CASC after exposure to high temperatures using a combined approach of experiments and numerical simulations. The simulation uses LS-DYNA software and a three-dimensional random aggregate mesoscopic model to analyze the process of concrete damage and crack propagation. Various mechanical parameters such as peak stress, peak strain, and compressive strength after exposure to different temperatures are calculated. The simulation results show that under quasi-static uniaxial compressive loading, microcracks initiate within the mortar and interfacial transition zone (ITZ) of CASC. These cracks then propagate through the coarse aggregates, leading to aggregate failure and the disintegration of the concrete structure. The macroscopic damage traits of CASC specimens reveal concentrated damage in the central region. As the temperature increases during heat treatment, the severity of damage to CASC specimens also increases. However, as the strength grade increases, the damage condition of CASC tends to improve.

Experimental crashworthiness analysis of corrugated-core sandwich panels under impact loading

ABSTRACT This research scrutinizes and contrasts the crashworthiness of single-core and two-core corrugated sandwich panels with varying configurations, influenced by crucial parameters like thickness, core angle, and foam filling. Experimental investigations encompass quasi-static compressive loads and low-velocity impact tests on these sandwich structures. Employing the design of the experiment (DOE) method, the study examines parameter impacts on initial peak crushing force (IPCF) and specific energy absorption (SEA) across three sequential steps. The fabrication phase involves creating square and trapezoidal aluminium sandwich panels bonded using specialized aluminium glue. The results notably highlight the pivotal role of corrugated sandwich panel thickness in enhancing crashworthiness, displaying a direct correlation between thickness and responses. Particularly, two-core configurations exhibit superior performance in reducing IPCF during low-velocity loading compared to other panels. These structures showcase exceptional capability in diminishing IPCF rates during low-velocity loading, surpassing even foam-filled panels and demonstrating superior crashworthiness among the tested configurations.

Research on the Load Bearing and Impact Resistance of a Novel Structure Exhibiting Both Positive and Negative Poisson’s Ratios

A ship equipment pedestal is a structure that connects power equipment to a hull. It must have a high load-bearing capacity and the ability to withstand large impact loads. In this paper, a novel structure with a positive-negative Poisson’s ratio is proposed. The deformation mechanism and mode of this structure under quasistatic compression loading are analysed via numerical simulation. Based on this new structure, a multicellular pedestal is designed, and its bearing capacity and impact resistance are analysed. The structural parameters of the pedestal are optimized. An experiment is conducted to evaluate the impact resistance of the pedestal model, which confirms that the proposed multicellular pedestal exhibits excellent impact resistance.

Experimental and numerical investigation on novel three-dimensional printed bio-inspired hexagonal lattices for energy absorption and stiffness behavior

In the current study, a new type of novel lattice structures with the concept of bio-mimicking three different nature-inspired designs from the honeycomb patterns, the overlapping phenomenon of the scales present on fish dermal layers, and scutes pattern observed from the top skin layers present on crocodile species are developed. These lattice structures are designed within a cubic volume of 30 mm. The design of lattice unit cells is made with two different geometrical sizes of 4 and 6 mm with different overlapping areas of 20, 30, 40, and 50% calculated from each cell area. All the unit cells’ walls are maintained at 0.4 and 0.6 mm only. The specimens are modeled and manufactured through the VAT photopolymerization process, one of the significant additive manufacturing principles for great dimensional accuracy with negligible defects in 3D printing (3DP). The research approach used to develop lightweight bio-inspired structures has been laid out, starting with observing design that served as inspiration. The cured 3D-printed specimens are examined under quasi-static compressive loading carried out on all specimens as per ASTM 1621 standards to measure the crashworthiness response of designed specimens. The energy ingestion capacity of all the specimens is assessed. A good correlation is observed between the experimental and numerical results for better validation. The best design parameters among all 16 specimens are identified for applying energy absorption applications in the automobile and aviation fields in real-time.

Direct measurement of the effective properties of an additively manufactured titanium octet truss unit cell using high energy X-ray diffraction

Additively manufactured lattice structures offer a high specific strength-to-density ratio in comparison to conventional, fully dense parts. The small feature size and intricate geometry of lattice structures make it challenging to directly characterize their mechanical properties. This study presents direct measurement of the elastic mechanical properties of an additively manufactured titanium alloy octet truss unit cell. Strut stress and strain were measured using high-energy X-ray diffraction during quasi-static compressive loading. The crystallographic stress-strain relationship was converted into the stress-strain relationship of the octet truss lattice unit cell using the known symmetry of the struts. The sample studied herein was best fit by an orthorhombic linear elastic stress-strain relationship. This technique shows promise for studying additively manufactured lattice structures at length scales not previously reported.

THE EFFECT OF DIFFERENT WINDING CONFIGURATIONS ON THE CRUSHING RESPONSE OF HELICAL WOUND WOVEN GLASS/EPOXY COMPOSITE TUBES

The crushing behavior of polymer matrix composite tubes depends on several factors, such as diameter, fiber orientation, wall thickness, and winding configuration. The current work aims at understanding the effect of winding configuration with different helical overlap portions (none, quarter, and half) and the number of layers on the crushing response of woven glass/epoxy composite tubes subjected to quasi-static compression and impact loading. The length-to-diameter ratio is kept constant, for all the cases of the specimen considered. Crashworthiness parameters, such as mean crushing load, initial peak load, specific energy absorption, and crush load efficiency are compared for different cases. Damage and failure characteristics of different helical wound composite specimens are examined and compared with straight wound composite tubes made with a winding angle of 0°. The study shows that the energy absorption capacity of helical wound specimens increases in almost the same proportion as the helical overlap portion increases from no overlap to half overlap. Also, experimental results for composite tubes having different helical overlap portions suggest that the helical overlap portion can be an important parameter in achieving tailor-made energy absorption properties with inbuilt triggering features.

Dynamic behavior of polyethylene terephthalate (PET) foam under compressive loads: Experimental and numerical study

The behavior of PET foam under quasi-static and dynamic compressive loads is analyzed. An experimental study is performed to evaluate its mechanical behavior and energy absorption characteristics at different strain rates. Also, a numerical model is developed to reproduce the dynamic compression behavior of the PET foam. Differences between the properties obtained in the quasi-static and dynamic tests show that the strength, stiffness and energy absorption efficiency are dependent on strain rate. The evolution of the Poisson ratio with strain and strain ratio is studied. A decrease in the Poisson ratio is observed as the strain rate increases.

Static and dynamic study of fiber-reinforced hemispherical stacked sandwich structure

Sandwich structures have garnered considerable attention due to their ability to meet the requirements of the aerospace and defense industry for impact resistance and lightweight performance. Unlike the plate or block construction investigated in previous studies, this present study proposes a new type of configuration known as the fiber-reinforced hemispherical stacked sandwich (FRHSS) structure. The fabrication of this FRHSS is achieved through the utilization of the Vacuum Assisted Resin Transfer Molding (VARTM) process and its response under quasi-static compression load is analyzed through both simulation and experiment. It is found that the internal configuration design effectively determines the direction of contraction in the hemispherical construction when it is subjected to quasi-static compression load. Furthermore, the impact resistance of the FRHSS against projectile penetration is also assessed. Through a comparison of simulation and experimental results, it becomes evident that the Chang-Chang failure criterion can successfully model the penetration process. Finally, the influence of internal configuration on the penetration resistance of the structure is studied by finite element method. The results show that the internal configuration plays an important role in the ballistic limiting velocity and ballistic performance of the construction. This study provides a valuable reference for the design of hemispherical sandwich structures.

Lightweight multi-layer graded pyramid folded structure based on tucked kirigami for green manufacturing

Lightweight structures are extensively utilized in various applications that demand exceptional mechanical properties and low densities, such as aerospace, vehicles, and construction components. However, the production of lightweight structures often entails significant material consumption and the emission of pollutants during the pressing and welding processes. Additive manufacturing (AM) has been hailed as a green technology that offers superior flexibility, reduces material wastage, and enables personalized design compared to traditional approaches. In this study, we present a novel lightweight multi-layer graded pyramid folded structure (PFS) based on tucked kirigami, with a focus on green manufacturing principles. The PFSs consist of nested pyramid cells connected by flat triangular plates. By leveraging stereolithography and a two-stage curing process, we achieve AM of multi-layer PFSs with excellent mechanical properties and shaping quality. Experimental studies were conducted on two-dimensional and three-dimensional graded PFSs under lateral and vertical quasi-static compressive loading to investigate the influence of gradient types and values on the mechanical performance of 3D printed PFSs. Our findings reveal that length gradients parallel to the load induce buckling deviations from the center, negatively impacting the performance of single-layer PFSs. Conversely, a height gradient along the z-direction further enhances specific energy absorption (SEA) and compressive strength. The results of this study provide a novel and viable approach to the design and manufacturing of multi-layer graded PFSs with programmable non-uniform stiffness. These graded PFSs hold significant potential for environment-friendly lightweight engineering applications.

Enhancing compressive performance in 3D printed pyramidal lattice structures with geometrically tailored I-shaped struts

This study examines the compressive response of geometrically tailored pyramidal lattice structures composed of struts with I-shaped cross-sections. Geometrically tailored pyramidal lattices with micro-scale features are 3D printed using the Digital Light Processing (DLP) technique, and their effective elastic modulus, collapse strength and energy absorption capacity are experimentally evaluated under quasi-static compressive loading. Furthermore, detailed non-linear finite element (FE) calculations are performed to examine underlying collapse mechanisms and explore the vast design space offered by the proposed geometrical tailoring scheme. Both the experimental and numerical results show that the geometrically tailored lattice structures outperform conventional pyramidal lattices of equal weight in terms of elastic modulus (+24 %), collapse strength (+21 %) and energy absorption (+68 %). Notably, these strength improvements are attributed to lateral buckling that prompts the I-shaped struts to bend sideways during collapse. Specific cross-sectional designs demonstrate remarkable enhancements in strength and energy absorption, reaching up to 93 % and 161 %, respectively, differentiating them significantly from conventional designs.

Crashworthiness performance of filament wound GFRP composite pipes depending on winding angle and number of layers

The main goal of this study is to enhance the crashworthiness performance of tubular composites to absorb more energy by optimizing the winding angle of their fibers. The crashworthiness performance of glass fiber-reinforced polymer composite pipes manufactured using the filament winding is investigated in detail. The effects of the winding angle of the fibers and thickness of the tube wall on the energy absorption were examined through quasi-static compression tests. The composite pipes were produced with 1200 tex E-glass fibers and Epikote 828 resin as the matrix material. The winding angles of ± 30°, ± 45°, ± 55°, ± 75°, and ± 90° were evaluated, and the number of the winding layers, ranged from 1 to 3, was also assessed. Quasi-static axial compressive loading was applied to 15 specimens using a hydraulic actuator. The results revealed that the one-layer specimens experienced buckling damage at low load levels, while an increase in the number of the layers led to higher load-carrying capacity and different types of damages. Furthermore, as the number of the layers increased, the load-carrying capacity and energy absorption of the specimens significantly improved. Progressive failure was observed in the specimens [± 90] for all the layers' configurations, with the specimen [± 90]3, having three layers, exhibiting the highest performance in terms of the load-carrying capacity and energy absorption. The failure modes indicated a combination of the fibers' separation, buckling, diagonal shear failure, and crushing in the upper and lower heads.