Impact Damage Mechanisms Research Articles

Low-velocity impact response and damage mechanism of cosine function cell-based lattice core sandwich panels

This study aims to investigate the impact response and damage mechanism of cosine-function cell-based (CFCB) lattice core sandwich panels. Several low-velocity impact tests were conducted to explore their advantages in impact resistance by comparing them with traditional body-centered cubic (BCC) lattice-core sandwich panels. The impact response and deformation patterns of CFCB lattice core sandwich panels with two different faceplate materials (aluminum alloy and carbon fiber reinforced plastic composite) were experimentally investigated. The CFCB lattice core sandwich panels exhibited higher impact resistance and energy absorption capacity than their BCC lattice core counterparts. Furthermore, sandwich panels with aluminum alloy faceplates provided better impact resistance capacity than those with CFRP faceplates. Subsequently, several numerical models were developed to explore the deformation mechanisms and energy absorption characteristics of CFCB lattice core sandwich panels. In addition, the effects of the core structural parameters on mechanical performance were numerically investigated. Results indicated that increasing the cell rod diameter and/or reducing the cosine period length could decrease the indentation depth and enhance crush force efficiency. Finally, based on the principle of minimum potential energy, a theoretical model was developed to predict the initial peak load of CFCB lattice core sandwich panels with isotropic faceplates. This study aimed to explore the impact response and provide design guidance for CFCB lattice core sandwich panels.

EXPLORING THE EFFECTS OF STITCHING PROCESS ON THE MECHANICAL PROPERTIES OF THREE- DIMENSIONAL (3D) STITCHED UNIDIRECTIONAL COMPOSITES

The stitching process has obvious effects on the out- of- plane mechanical properties of composites such as impact damage mechanism or impact energy absorption. However, the effects on the in- plane mechanical properties of composites have been under discussion and need to be clarified. In the previous studies, tensile, shear and bending behaviors of 3D stitched biaxial woven carbon composite were investigated. The unidirectional carbon woven fabrics constitute the significant part of raw materials in the composite industry. For this reason, the research study was expanded to examine the in- plane mechanics of 3D stitched unidirectional carbon woven composites. In this study, the unstitched and 3D stitched unidirectional woven carbon composites were manufactured and tested under the shear, tensile and bending loads. While the stitching process improved the tensile and shear modulus of composite, it could not create the significant difference in the bending behavior. The highest module and maximum stress values were obtained in the tensile test. The bending and shear test results follow them, respectively. Moreover, it was proven that the fabric architecture of stitched composite layer has the substantial effect on the tensile properties of 3D stitched composite.

Low-velocity impact behavior and damage mechanisms of honeycomb sandwich structures with elastomeric interlayers in CFRP skins

Elastomers help improve the toughness of lightweight high-strength materials, offering significant potential for enhancing the mechanical properties. However, introducing elastomers into CFRP interlayers as skin for composite sandwich structures has not yet been explored regarding the impact responses of such novel structures. This paper, for the first time in literature studies the low-velocity impact behavior and damage mechanisms of this novel sandwich structure using a combined experimental and numerical approach. The experimental results of sandwich structures with and without elastomer layers under different impact energies are presented. Finite element models of the two sandwich structures are built and impact behaviors were compared. The differences in internal damage and energy distribution during the impact are investigated to explain the reasons for the differing impact responses of the two sandwich structures. The results reveal that elastomeric interlayers have a significant advantage in enhancing the damage resistance of composite sandwich structures, especially under high impact energy conditions. The key contributions of this paper include the experimental characterization of the impact behavior of composite sandwich structures with elastomeric interlayers, and the explanation of the reasons for the changes in impact responses caused by the elastomers from the perspectives of damage mechanisms and energy distribution.

Dynamic damage behavior of auxetic textile reinforced concrete under impact loading

To investigate the dynamic compression behavior of Textile-reinforced concrete (TRC) under impact load, low speed and high speed impact tests were performed using a ball drop test and a split Hopkinson pressure bar (SHPB) with ϕ50mm, respectively. In view of the advantages of auxetic materials in impact resistance and energy absorption, the auxetic fiber preforms with negative Poisson's ratio effect were woven into meshes and added to the cement-based materials to obtain the auxetic textile-reinforced concrete. Thus, the auxetic textile reinforced cement-based material is obtained. In this paper, TRC with different textile types, laying layers and surface treatments were prepared, and impact tests with different impact speeds were carried out to evaluate the impact resistance of TRC. The impact damage behavior of TRC was analyzed through the method of digital scattering analysis, and then the impact damage mechanism of TRC was investigated. The results show that the auxetic effect of auxetic textiles can still be stabilized under impact loads of different velocities, which provides better control of deformation and energy consumption in the matrix material. Under different impact heights of falling balls, the impact fracture energy of cementitious materials reinforced with auxetic textiles was increased by up to 22.5 and 20 times, respectively, compared with that of blank samples.

Effects of explosion-venting interlayer within utility tunnels on the characteristics of natural gas explosions

With the rapid expansion of the national economy and strategic adjustments to the energy structure, natural gas, a crucial clean energy source, encounters significant safety challenges during transportation in utility tunnels, owing to its flammable and explosive nature. To effectively address the current issues in response technologies for gas explosions in utility tunnels, such as inadequate control over the flame propagation range, limited attenuation of overpressure, and the mechanical impact damage effects on the internal structures of the utility tunnels and surrounding buildings, a small-scale experimental platform was constructed independently. This platform is designed to explore how the area and position of vents affect the characteristics of methane explosions within tunnels, utilizing the explosion venting mechanism. The results indicate that, for the same venting position, the maximum flame propagation distance, speed, and peak overpressure all decrease as the venting area increases. When the vent is located at position 1 in each compartment, the reduction in maximum flame propagation distance and speed is the most significant. The maximum decrease in peak overpressure occurs at venting position 2. When the venting position is closer to the ignition source, the rate of explosion overpressure rise and the explosion index both decrease with an increase in venting area, with the most significant reduction occurring at venting position 1. Conversely, when the venting position is farther from the ignition source, the rate of explosion overpressure rise and the explosion index actually increase, with the most significant increase occurring at venting position 4. The research findings offer a theoretical foundation and scientific guidance for developing new technologies aimed at mitigating gas explosion disasters in utility tunnels through internal venting.

The low velocity impact properties of three- dimensional (3D) warp interlock woven composites according to the fabric architecture

Three-dimensional (3D) warp interlock woven composites (3DWIWC) are in demand in various industries due to their excellent delamination resistance, damage tolerance and fracture toughness properties. The 3D warp interlock woven fabric architecture can be defined by numerous fabric parameters such as: the binding and stuffer warp yarns, the woven pattern, the presence of yarn groups, etc. …. The effect of the fabric architecture on the impact behaviour of 3DWIWC made with carbon yarns has not been fully investigated. The binding warp yarns with the weave pattern play the main role in the arrangement of yarns within the final composite. In order to highlight their main influence, the 3D woven composites had been differentiated according to the main fabric architectural parameters, which are the angle and depth of binding warp yarn, presence of stuffer warp yarn and weave pattern of binding warp yarn. Afterward, their low velocity impact properties and damage mechanisms were examined. Thanks to the precise combination of these internal parameters of the fabric architecture, the contact force and absorbed energy values of 3DWIWC could be increased almost %50 and %15, respectively. Moreover, their damage mechanisms could be significantly improved.

Study on impact wear and damage mechanisms of DLC films on TC4 and 9Cr18 alloys

As a classic film-resistant coating, DLC film is widely used in the field of impact wear. The impact wear properties of DLC films with different thicknesses (1.1 μm thin DLC film and 7.9 μm thick DLC film) on various substrates (9Cr18 and TC4) were evaluated. On the TC4 substrate, the experimental results demonstrate that the thick DLC film offers obvious damage and serious impact wear, but the thin DLC film exhibits reduced deformation and wear. On the 9Cr18 substrate, both thick and thin DLC films work successfully in protecting the substrate. The failure mechanisms of the two DLC films are mainly abrasive wear (thin DLC film) and adhesive wear (thick DLC film). The thin DLC film with the highest hardness, toughness, and adhesion represents the best protective coating for impact dynamic load applications examined, regardless of whether the substrate is soft or hard.

Study on the elastic impact deformation behavior and damage mechanism during the polishing process of PS@CeO2 core-shell abrasive

Discrete element simulations were carried out to investigate the elastic impact damage mechanism of PS@CeO2 core-shell abrasive (CSCAP). Aiming at understanding the deformation behavior and damage mechanism of CSCAP during the polishing process, effects of the impact velocity, impact angle on the rates of deformation and recovery deformation, stress distribution, the number of microcracks were systematically investigated. Tensile cracks formed owing to the CSCAP deformation was gradually increasing when impacting the workpiece downwards. After the CSCAP reached the maximum deformation, macroscopic cracks at the interface were extended gradually. Owing to the redistribution of the compressive force, the interface was observed to predominantly occur in shear cracks, while the shell layer was found to be distributed with tensile cracks. The number of microcracks increase with the increase in impact speed, the impact angle was within the range of 15° to 45°. This investigation enhances the comprehension of nanoscale deformation damage mechanism in CSCAP during ultra-precision machining processes.

Dynamic responses and damage/element composition analysis of thermoplastic polyamide reinforced epoxy composites exposed to HCI environment

AbstractThe present study aimed to examine how the corrosive environment affected the low‐velocity impact (LVI) characteristics and damage mechanisms of thermoplastic polyamide fiber‐reinforced polymer (PFRP) composites. In this regard, composite specimens were subjected to corrosive environment containing 10 wt.% diluted HCl for one week and one month before LVI tests. To investigate the hostile effects of the corrosive environment on the composites, scanning electron microscope (SEM) coupled with energy‐dispersive X‐ray system (EDX) analyses were carried out, and thus variations in the elemental composition and damage mechanisms for the composites were determined. According to the examinations, it was discovered that the degradation in LVI responses, such as contact stiffness, bending stiffness, and peak force, increased with longer aging time, as expected. Furthermore, when the aging effect was assessed based on absorbed energy, the specimens exposed to a corrosive environment for one month exhibited the highest energy absorption compared to the control and 1‐week‐immersed ones. The degrading effect of the HCI environment appeared as higher damage severity on the composites, which was also detected from the SEM images. According to the SEM analyses, matrix cracks, corrosion pits, and local surface imperfections caused by ion exchange are detected in 1‐week‐immersed specimens, while more serious damage mechanisms such as fiber breakage and fiber pull‐out are noted in specimens exposed to corrosive environment for 1 month. Furthermore, approximately 6.33 wt.% CI was identified in the composites after 1 month of aging, which was associated with the hydrolysis triggered by rise in the composite's damage severity.Highlights Aging effects in mechanical properties of PFRP composites were investigated LVI tests were conducted to determine dynamic responses of aged composites Longer aging time led to more severe damages such fiber rupture, delamination etc. PFRP composites absorbed at least 68% of impact energy.

Mechanical behavior and fiber reinforcing mechanism of high-toughness recycled aggregate concrete under high strain-rate impact loads

Fiber-reinforced recycled aggregate concrete (FRRAC) is renowned for its excellent mechanical properties and environmental benefits, making it a popular choice in construction engineering. However, the impact damage mechanisms of FRRAC remain unclear. This study leverages advanced in-situ 4D CT technology to investigate the fiber-reinforcing mechanisms of High-Toughness Recycled Aggregate Concrete (HTRAC) using construction waste as a sustainable building material. Under high strain-rate conditions, the dynamic mechanical behaviors of both plain recycled aggregate concrete (PRAC) and HTRAC were examined using the Split Hopkinson Pressure Bar (SHPB) method. The experiments revealed significant strain rate sensitivities in both materials, with HTRAC showing superior fiber reinforcement that markedly enhances its toughness. Quantitative models for dynamic increasing factors of key mechanical parameters, including peak stress, peak strain, initial elastic modulus, ultimate strain, and toughness index, were developed. These findings offer critical design insights for using HTRAC in impact load conditions and other extreme environments, promoting its wider adoption in the construction industry.

Effect of boundary conditions on the low‐velocity impact damage mechanism of fiber metal laminate

AbstractThe boundary condition is a very important factor when characterizing the impact performance of a material or a structure. However, its effect on fiber metal laminate (FML) has been rarely mentioned. In the present investigation, three levels of low‐velocity impact tests were conducted on the glass fiber reinforced aluminum laminate (Glare) under two different boundary conditions, one was that defined in ASTM D7136 and another one was self‐designed that has the same constraint area but different constraint degree. One basis of the experiments, finite element analyses were performed to gain a deeper understanding of the different damage mechanisms. With which another three boundary conditions were investigated for further considering the effect of constraint areas on both the impact and non‐impact sides, including that defined in another commonly used standard ASTM D5628 and two self‐designed cases. It was indicated that the boundary conditions influenced less the force and energy responses of Glare laminate, regardless of the impact damage levels, and hardly on the damage behavior as well when perforation was encountered. However, influences were obtained under lower and intermediate damage levels, and it was the constraint area on the rear side and constraint degree that played the dominant roles, respectively. The results achieved can provide suggestions for reasonably evaluating the low‐velocity impact performance of FML.Highlights Comparisons were made between the low‐velocity impact behavior of Glare laminates under five different boundary conditions. Boundary conditions influenced hardly on maximum impact force and energy absorbed ratio, but evidently on damage behavior. Constraint area and constraint degree governed damage mechanism under lower and intermediate impact energies, respectively. Influence of boundary conditions on damage behavior disappeared when the impact energy was enough to perforate Glare laminate.

Impact response characteristics and damage mechanism of continuous carbon-fiber-reinforced magnesium matrix composite materials

The continuous carbon-fiber-reinforced magnesium matrix composite (C_f/Mg) is a new type of composite material made of a magnesium alloy sheet and carbon-fiber-reinforced composite material with alternating layers. It has the advantages of high damage tolerance, light weight, and corrosion resistance, and has become the first choice of lightweight materials in aerospace, transportation, and other fields. Because impact-resistance serves as an important index for its structural design and performance stability, a continuous carbon-fiber-reinforced magnesium matrix composite with indirect bonding using a modified epoxy resin was designed in this study. Moreover, C_f/Mg was chosen to be the object of research through the selection of constituent materials such as magnesium alloys, carbon fibers, resins, and other properties, which matched the aim of realizing a lightweight material. With the help of hot-compression molding technology, dynamic impact mechanical behavior, and damage analysis technology, the structural design and preparation process optimization of epoxy resin carbon-fiber prepregs and magnesium alloy layer materials, as well as the dynamic impact mechanical response characteristics and damage evolution process under different impact energy conditions, were studied. Accordingly, through a combination of low-velocity impact experiments and numerical simulations, the effects of continuous multiple impacts at the same location with the same impact energy, as well as impacts with the same impact energy and different punch diameters, on the low-velocity impact damage behavior and dynamic impact response characteristics of C_f/Mg were investigated. The results of this study show that when the 5J impact is applied four times consecutively, the peak impact load gradually increases with the increasing number of impacts. Moreover, the peak impact loads of the second, third, and fourth impacts increase by 6.09%, 10.7%, and 14.5%, respectively, compared with the results of the first impact.

Numerical simulation of the effect of projectile shape and size on the high-velocity impact of carbon fiber reinforced composite laminates

To investigate the impact response and damage mechanism of CFRP composite materials for high-speed trains under high-speed impact from foreign objects of different shapes and sizes, high-speed impact experiments and simulations were conducted on CFRP composite laminate at a velocity of 163 m/s. A finite element simulation model was established in Abaqus/Explicit. This model adopts the 3D-Hashin failure criterion considering strain rate effects to simulate the failure of fibers and matrix. Bonded elements with zero thickness were inserted along the fiber direction in the laminate to replicate the damage phenomena of fiber bundle debonding and pull-out. The effectiveness of the finite element model was validated by high-speed photography of the impact process and ultrasonic C-scan damage images recorded during the experiments. Based on this simulation model, the influence of projectiles of different shapes and sizes on the impact response of CFRP composite materials was studied. Projectiles of different shapes exhibit their own characteristics in terms of the time of peak force occurrence, manifestation, and characteristics of laminar damage. The peak force of the cylindrical projectile is 245.01% greater than that of the spherical one, while the conical projectile is 52.26% smaller than the spherical one. When the projectile size increases from 10 mm to 20 mm, the peak force of the spherical projectile, conical projectile, and cylindrical projectile increases by 79.67%, 120.12%, and 283.13% respectively. The total area of delamination in laminated plates is positively correlated with the size of the impacting body.

Dynamic response and damage behavior of impact wear for polycrystalline diamond compact under low kinetic energy impact

Polycrystalline diamond compact (PDC) cutters are the main load-bearing components in shale gas drilling, and their performance significantly affects the efficiency of shale gas extraction. One of the primary reasons for cutter failure is the dynamic impact between the rock and the cutter due to the complex geological conditions of shale gas extraction. Investigating the impact wear behavior and damage mechanisms is vital to designing superior-performing PDC structures and improving their effectiveness in engineering applications. This work investigates the kinetic response and damage behavior of PDCs under low kinetic energy impacts to explain the characteristics and mechanisms of PDC impact wear. The results show that the impact force fluctuates with impact owing to changes in the interface state. Owing to the elastic-plastic properties of PDC, 87 % of the kinetic energy is used for plastic deformation and fracture. Secondly, the contact time and kinetic energy absorption rate only relate to the impact mass. The contact time positively correlates with mass, while the kinetic energy absorption rate changes in the opposite direction. In addition, diamond fracture occurs with a low kinetic energy accumulation of only 0.059 J. Cobalt catalysis and stress effects were found to induce graphitization and carbon rehybridization jointly during impact wear. It is concluded that the PDC impact wear mechanism under low kinetic energy impact is a brittle fracture with a combination of transcrystalline fracture and intergranular fracture. This work provides referable basic research data for designing impact-wear resistant PDC structures and improving the efficiency of shale gas extraction.

Study on the Low-Velocity Impact Response and Damage Mechanisms of Thermoplastic Composites.

A comparative experimental and numerical study of the impact behaviour of carbon-fiber-reinforced thermoplastic (TP) and thermoset (TS) composites has been carried out. On the one hand, low velocity impact (LVI) tests were performed on TP and TS composites with different lay-up sequences at different energy levels, and the damage modes and microscopic damage mechanisms after impact were investigated using macroscale inspection, C-scan inspection, and X-ray-computed tomography. The comparative results show that the initial damage valve force under LVI depends not only on the material, but also on the layup sequence. The initial valve force of the P2 soft layer with lower stiffness is about 11% lower than that of the P1 quasi-isotropic layer under the same material, while the initial valve force of thermoplastic composites is about 28% lower than that of thermoset composites under the same stacking order. Under the same stacking order and impact energy level, the damage area and depth of TP composites are smaller than those of TS composites; while under the same material and impact energy level, the indentation depth of P2 plies is greater than that of P1 plies, and the damage area of P2 plies is smaller than that of P1 plies, but the change of thermoplastic composites is not as obvious as that of thermoset composites. This indicates that TP composites have a higher initial damage threshold energy and impact resistance at the same lay-up order, while increasing the lay-up ratio of the same material by 45° improves the impact resistance of the structure. In addition, a damage model based on continuum damage mechanics (CDM) was developed to predict different damage modes of thermoplastic composites during low velocity impact, and the analytical results were compared with the experimental results. At an impact energy of 4.45 J/mm, the error of the initial damage valve force is 5.26% and the error of the maximum impact force is 4.36%. The simulated impact energy and impact velocity curves agree with the experimental results, indicating that the finite element model has good reliability.

Impact Fracture Resistance of Fused Deposition Models from Polylactic Acid with Respect to Infill Density and Sample Thickness

Fused deposition modeling (FDM) is widely employed in prototyping due to its cost-effectiveness, speed, and ability to produce detailed and functional prototypes using a variety of materials. Simultaneously, consideration for the use of biodegradable polymers and a general reduction in their usage while enhancing the production of polymer-based products is at the forefront of sustainable practices and environmental consciousness. This study investigates the impact fracture resistance of FDM models fabricated from Polylactic Acid (PLA), examining the influence of infill density (50% and 100% infill) and sample thickness (2 mm, 3 mm, and 5 mm). Optical microscopy, FTIR spectroscopy, and SEM analysis of PLA filament and fractured FDM PLA surfaces in impacted samples were conducted to ascertain the influence of process parameters on impact damage and failure mechanisms. The results indicate that a 100% infill profile with a 2 mm thickness should be avoided due to unpredictable behavior under impact. Conversely, a 5 mm thickness demonstrates significantly higher durability in comparison to a 50% infill profile. Optimal impact strength is observed in samples with a 3 mm thickness, suggesting potential material savings with 50% infill without compromising mechanical properties. The findings contribute valuable insights for refining FDM parameters and advancing the understanding of material behaviors in sustainable manufacturing practices.

Experimental Research on the Impact Resistance Mechanical Properties and Damage Mechanism of Rubberized Concrete under Freeze–Thaw Cycling

To improve the long-term performance of concrete engineering in high-altitude areas, waste tire rubber was added to a concrete mix, and freeze–thaw and impact tests were conducted. The effects of waste tire rubber with different particle sizes (10, 20, 30 mesh) and freeze–thaw cycles (0, 25, 50, 75, 100, 125) on the dynamic mechanical properties of concrete materials were studied. The stress–strain curves, peak stress, and fracture morphology of the specimens were analyzed. The microstructure changes of the specimens were also analyzed using scanning electron microscopy (SEM). The results showed the following: (1) Both macroscopic and microscopic analysis results showed that the internal damage of rubber concrete specimens was smaller after freeze–thawing, and the integrity was better after impact, maintaining a loose but not scattered state. The addition of waste tire rubber significantly improved the material’s impact resistance to a certain extent. (2) As the impact pressure increased, the strain rate of the specimens increased linearly, and the dynamic peak stress was linearly positively correlated with the strain rate. (3) After 125 freeze–thaw cycles, the peak stress of the specimens with 30-mesh added rubber decreased significantly less than that of ordinary concrete under 0.3, 0.45, and 0.6 MPa impact pressure. The dynamic peak stress was higher than that of specimens with 10-mesh and 20-mesh added rubber, and the addition of 30-mesh rubber significantly improved the frost resistance and impact resistance of concrete materials. This study can provide new ideas for the engineering application of rubber concrete.

Tensile impact behaviors and damage mechanism of woven carbon fiber-reinforced-polymer laminates considering adiabatic shear band

In this study, the tensile impact behavior and damage mechanism of a two-dimensional woven carbon-fiber-reinforced-polymer (CFRP) laminates under different high strain rates are investigated. The damage morphologies are illustrated and studied using meso-macroscale finite element analysis (FEA) and Split Hopkinson bar (SHB) test, FEA results are compared and validated with the SHB test results, and proved to be correct with enough accuracy. The matrix crack first appeared, the tensile stress wave propagated along the interface, which causes shear failure at the interface, which dominated the failure of the specimen and formed adiabatic shear bands inside each ply, the adiabatic shear bands begin to develop in areas with interfacial damage, they are formed after structural damage and propagate in the direction of the interface, accompanied by damage evolution. High strain rate 1400, 1600, and 2400 s−1 impacts tend to lead to direct failure of composite laminates compared to low strain rate 600, and 800 s−1 impacts, the Young’s modulus with high strain rate 1400, 1600, and 2400 s−1 are more than twice as much compared to low strain rate 600, and 800 s−1. The plain-woven CFRP laminates is characterized with strain-rate-hardeningeffect and strain rate sensitivity, with increase of high strain rate from 600 to 2400 s−1, the Young’s modulus increases from 8.91 to 35.7 GPa, whereas the yield strength increases from 397 to 1298 MPa. The delamination occurs between the plies after crack generation inside the epoxy resin matrix, and begins at a certain strain value after the elastic phase, the micro-cracks propagated along the fiber bundle-matrix interface, thus causing interfacial debonding due to shear stress, these factors result in a strain-rate hardening effect.

Finite element analysis of the effect of crystallinity on low-velocity impact performance of poly (aryl ether ketone) composites

A new copolymer poly (aryl ether ketone) (PAEK) resin was used as a matrix to prepare carbon fiber (CF) reinforced composites with different crystallinity by slow and rapid cooling. Finite element (FE) models were constructed according to micromechanics, and the progressive damage method based on the three-dimensional (3D) PUCK damage criterion was used to analyze the low-velocity impact damage mechanism of the CF/PAEK composites. The experimental results show that the composites with lower crystallinity have higher impact resistance and smaller impact damage area. In the FE simulated impact damage evolution process, the damage of the impact side is mainly compressive damage of the matrix and the fiber, while that of the impact back side is mainly tensile damage of the matrix. Moreover, due to their high interfacial bonding strength, the main damage modes of rapid-cooled composites with lower crystallinity are severe matrix tensile damage and slight fiber tensile damage in the impact back side. However, the slow-cooled composites show more delamination. In addition, for the damage evolution of compression after impact, the FE simulation shows that fiber compression, matrix tension, matrix compression and delamination expand along the transverse to the compression load. Furthermore, the in-plane damage expansion occurs earlier in the rapid-cooled composites, which also have graver interlaminar damage.

Design and experiment of the simulated electronic corn ear based on UWB/IMU technology

In order to explore kinematic and dynamic parameters of corn ear in the process of threshing, and reveal threshing principle and grain impact damage mechanism, a simulation electronic corn ear was designed based on ultra wide band (UWB) and inertial measurement unit (IMU) technology. The spatial positioning algorithm and impact force analysis algorithm of electronic corn ear were studied, and a simulated threshing test bench was built. Then free fall impact force detection test and comprehensive performance test of the electronic corn ear were carried out. The experimental results showed that the average detection error of free fall impact force was about 0.69 N, with an accuracy more than 95 %, and the average detection error of impact force in the process of simulation threshing was about −0.27 N, with an accuracy more than 97 %. The spatial positioning accuracy of electronic corn ear was related to the number, layout and positioning algorithm of UWB positioning base station. Unscented kalman filter (UKF) tight combination positioning algorithm had the highest positioning accuracy (about 100 % probability of positioning error within ± 0.15 m) under the condition of non-line of sight (NLOS) (5 base stations, 3.2 m height difference). Extended kalman filter (EKF) tight combination positioning algorithm had the second highest positioning accuracy (about 100 % probability of positioning error within ± 0.2 m), followed by kalman filter (KF) loose combination, UWB single positioning and IMU single positioning algorithm. The results are helpful for obtaining kinematic and dynamic parameters in the process of ear threshing and separation, understanding the mechanism of efficient and low-damage threshing, and provide a basis for the segmented optimization design of subsequent devices.