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The response of plane-parallel 2 mm thick samples of 47.3Ni-52.7Ti alloy was studied in two series of planar impact tests at temperatures between 300 and 473 K and between 473 and 318 K (heating to 473 K followed by cooling). In two additional series, the samples of 0.4–4 mm thickness were tested at 300 and 338 K (after preheating up to 473 K). In all the tests, the samples were loaded by 1 mm thick copper impactors having velocities equal to 314 ± 2 m/s. The velocity of the rear sample surface was continuously monitored by a laser Doppler velocimeter. It was shown that substantial, by an order of magnitude, variation of Hugoniot elastic limit σ H E L and compressive strength Y of the nitinol with temperature are caused by the martensite–austenite transformation and its reversal. The variation of the dynamic tensile (spall) strength σ s p of the nitinol along the heating–cooling path was found similar to that of σ H E L although the difference between σ s p values of austenite and martensite, ∼20%, is much more modest than in the case of σ H E L . The test series performed at constant temperatures with samples of different thicknesses allows one to conclude that the plastic deformation in shocked austenite is presumably realized by dislocation motion and multiplication controlled by phonon viscosity. In the shocked martensite, the plastic deformation mechanism at a stress lower than ∼0.3 GPa is likely a thermally activated combination of deformation twinning and slip of kinking dislocations. [ABSTRACT FROM AUTHOR]

Composite materials are widely preferred in the aviation, automotive, construction and maritime industries due to their many superior properties. As a result of this widespread use, composite structures are inevitably subjected to various environmental conditions. Various environmental conditions may negatively affect the mechanical performance of the structure, and the structure may become unable to maintain its initial mechanical properties, especially in the face of critical loading, such as low‐velocity impacts. This research investigated the influence of various environmental conditions on the low‐velocity impact strength of composite materials. 12‐layer plate samples with epoxy matrix reinforced with woven glass fabric (GF), woven carbon fabric (CF), and hybrid fabric (HF), where the two fabrics are used together, were produced. Low‐velocity impact tests were conducted to these specimens at 20 and 40 J energy levels. Damages occurring in the material as a result of the low‐velocity impact test were interpreted using high‐resolution camera and optical microscope images. Force‐time and force‐ displacement curves were drawn and interpreted. It was concluded that as the impact energy values increased, the maximum force and displacement values also increased. Highlights: The influence of various environmental conditions to which composite materials may be exposed on the dynamic response of the structure has been investigated.Various environmental conditions significantly affected the composite structure's impact behavior.While glass fabric (GF) composite samples were more affected by the seawater environment, carbon fabric (CF) composite samples were more affected by the HCl environment.Hybrid (HF) composite samples were affected by seawater and HCl in approximately equal amounts. [ABSTRACT FROM AUTHOR]

The load‐bearing capacity and failure characteristics of composite structures are closely related to their dimensions. In this study, low‐velocity impact, ultrasonic non‐destructive testing, and compression after impact tests were conducted on composite laminates of varying widths to investigate the influence of size effects. Distinct impact response profiles and compression failure modes were characterized. The results indicate that under impact loading, the delamination threshold load (6700 N ~ 7200 N) and the knee‐point energy (40 J) are not affected by width. However, variations in width lead to differences in indentation depth, impact duration, peak load, delamination characteristics, and energy absorption. Furthermore, increasing impact energy further magnifies these differences. Under compression loading, wider laminates exhibit lower residual strength, with the influence of impact energy on residual strength decreasing as width increases. Importantly, the observed compression failure deformation mode transitions from localized buckling to widespread sub‐layer delamination‐induced compression failure. This suggests that changes in width alter the governing mechanical mechanisms of CAI failure. Consequently, the use of a single‐size laminate to represent both LVI and CAI processes is not recommended. Based on experimental results, the reliability of the equivalent damage method in predicting the residual compression strength of laminates of different widths was confirmed, providing valuable insights for practical engineering applications. Highlights: Assess the variations in the low‐velocity impact process of laminates with different widths.Evaluate the delamination damage of laminates after impacts by ultrasonic C‐scan techniques.Investigate the effect of variation in widths on the compression behavior of laminates after impact.Validate the feasibility of equivalent damage modeling for calculating residual strength. [ABSTRACT FROM AUTHOR]

Thermoplastic composites have a high application demand in aerospace, marine military and other cutting‐edge industry. However, it poses a considerable obstacle in achieving three‐dimensional (3D) thermoplastic composites because of the inadequate infiltration of highly viscous thermoplastic resins. In this paper, high‐toughness Polyetheretherketone (PEEK) resin‐based 3D orthogonal carbon fiber thermoplastic composites were designed and obtained. Low‐velocity impact test was conducted on 3D orthogonal woven composite (3DOWC) under the energy levels of 5 and 10 J, and its performance was compared with that of the 2D unidirectional layup composite (2DULC) and the 2D plain layup composite (2DPLC). The results showed that 3DOWC possessed superior elastic energy absorption capacity and less damage morphology compared to 2D composites. 3DOWC had the highest contact force value of 2420.25 N at 10 J, which is 36.83% higher than that of 2DPLC. Furthermore, a finite element model in multi‐scale was established to investigate the damage evolution and failure mechanism of the 3D orthogonal woven CF/PEEK composites. The damage morphology observed in both experimental and numerical findings demonstrated that the matrix shedding, while the yarn fractured on the nonimpact side beneath the impact point. Additionally, enhancing the tensile strength of the yarn in the bottom layer can lead to further improvement in impact resistance. This work provides an innovative method for manufacturing 3D thermoplastic composites and lays the foundation for the impact simulation analysis of such composites. Highlights: A novel approach was introduced for fabricating 3D carbon fiber/PEEK composites, which exhibits remarkable resistance to impact.A comprehensive investigation was conducted to evaluate the impact properties of 3D thermoplastic composite compared to 2D composite.A finite element model in multi‐scale including failure criteria was established to simulate the damage evolution. [ABSTRACT FROM AUTHOR]

AbstractThis paper presents a study on the characterization of the moderate energy impact response between the elastic-plastic plate and the elastic-plastic sphere. An equivalent contact stiffness is proposed to substitute the linear contact stiffness, and a universal analytical expression is presented according to the intensive FE simulations for different material combinations under moderate impact energy. Then, a modified characterization diagram is suggested using the analytical expression. The modified diagram is validated by the FE simulations and experimental results. The results show the modified diagram can predict the maximum impact force and the response type in a fast and simple way. [ABSTRACT FROM AUTHOR]

The responses of sandwich cylindrical shells containing fluid to free vibrations and low-velocity impact were studied. The high-order shear deformation theory and Bernoulli's equation for the structure-fluid interface were used. To solve the equations obtained and validate the results, the Galerkin method and Abaqus finite element software were employed. The main innovation of this research is the calculation of the effective mass of the top layer and the entire sandwich cylindrical shell containing fluid using displacement field relations, their equivalent density, and indentation force due to impact. In addition, to calculate the impact force and the structure-fluid interaction, a two-degree-of-freedom model of mass, spring, and damper with the effect of the crushing resistance of the core was used. The results show that the fluid is an important and effective factor in calculating the natural frequency and low-velocity impact on the structure. The presence of fluid reduces the fundamental natural frequency of the sandwich cylindrical shell by 69%. Parameters such as core and layer thickness, length, and radius of the sandwich cylindrical shell, presence of the fluid, various boundary conditions, wave number, fiber orientation angles, velocity, and mass of the impactor are essential and influential factors in studying vibrations, impact, and optimal design of structures. [ABSTRACT FROM AUTHOR]

In addressing the challenging issue of impact source localization for large-scale anisotropic stiffened compartmental cylindrical shell structures, this paper presents a novel impact localization method. The method is based on a time-reversal virtual focusing triangulation approach and does not rely on prior knowledge of the structure or specific measurements of wave velocity. By employing energy power filtering to select key sensors, wavelet packet decomposition is utilized to extract narrowband Lamb wave signals, which are then synthesized. Further enhancement of signal recognition is achieved through time-reversal amplification techniques. Experimental results demonstrate that under non-motorized operating conditions, this method achieves an average error of 0.89 m. Under motorized operating conditions, the average error is 1.12 m. Although the presence of background noise leads to an increase in error, the overall localization performance is superior to traditional triangulation methods. Additionally, selecting the top three sensors in terms of energy power ranking can more accurately record impact response. [ABSTRACT FROM AUTHOR]

Flax and carbon fibers reinforced polymer composites have high potentials to be used as sustainable building materials. To understand the impact resistance of these fiber composites, the present article studied the impact resistance of unidirectional flax fiber and carbon fiber reinforced polymer (FFRP and CFRP) composite plates. The impact response, damage resistance, and impact tolerance were investigated using drop hammer impact and compression after impact (CAI) tests. The internal damage of FFRP and CFRP due to impact loads was studied using acoustic emission technology. In addition, the development process of impact damage was analyzed. CFRP plates show a higher specific energy absorption rate than that of FFRP, because of the more serious internal damage and brittle fracture tendencies. Matrix cracking was the primary damage in FFRP and CFRP under impact load. Compared with CFRP, FFRP possesses a higher CAI due to less damage. Further expansion of the matrix crack caused by the original impact occurs in the impacted fiber-reinforced polymer composites (FRP) under a compressive load. [ABSTRACT FROM AUTHOR]

In this study, the high velocity impact response of a lightweight composite structure comprising an aramid honeycomb core sandwiched between two aluminum sheets was investigated against conical and hemispherical projectiles. It used a pneumatic gas gun and Abaqus software to conduct experimental and numerical research, respectively, focusing on damage behavior and failure modes, with a systematic parametric and optimization study for optimum ballistic performance. Results revealed that varying the rear sheet thickness and cell length had the most significant effects. Overall, the multifaceted approach advances the development and optimization of advanced composites for impact-resistant technologies where weight savings are critical. [ABSTRACT FROM AUTHOR]

Thermoplastic composite organosheets (OSs) are increasingly recognized as a viable solution for automotive and aerospace structures, offering a range of benefits including cost-effectiveness through high-rate production, lightweight design, impact resistance, formability, and recyclability. This study examines the impact response, post-impact strength evaluation, and hot-pressing repair effectiveness of woven glass fiber nylon composite OSs across varying impact energy levels. Experimental investigations involved subjecting composite specimens to impact at varying energy levels using a drop-tower test rig, followed by compression-after-impact (CAI) tests. The results underscore the exceptional damage tolerance and improved residual compressive strength of the OSs compared to traditional thermoset composites. This enhancement was primarily attributed to the matrix's ductility, which mitigated transverse crack propagation and significantly increased the amount of absorbed energy. To mitigate impact-induced damage, a localized hot-pressing repair approach was developed. This allowed to restore the post-impact strength of the OSs to pristine levels for impact energies below 40 J and by 83.6% for higher impact energies, when OS perforation was observed. The measured levels of post-repair strength demonstrate a successful restoration of OS strength over a wide range of impact energies, and despite limitations in achieving complete strength recovery above 40 J, hot-pressing repair emerges as a promising strategy for ensuring the longevity of thermoplastic composites through repairability. [ABSTRACT FROM AUTHOR]

Due to the nonlinearity of the contact interface, as well as the material, jointed structures exhibit complex mechanical behaviors under impact loading. In order to accurately characterize the dynamic response of a joint, this work presents a nonlinear dynamic model (DICF model). First, the effects of loading velocity, preload and friction coefficient on the displacement–load curve are discussed based on a validated finite element model. Numerical simulation results show that the critical load and critical displacement are linearly related to the normalized logarithmic velocity and linearly related to the normalized preload and friction coefficient. Subsequently, a DICF model that consists of sliding, collision and failure is proposed. The constitutive relations of the model are derived, and dynamic correction functions are introduced to characterize the effects of velocity, preload and friction coefficient. A parameter identification method for the model is also provided. Finally, the DICF model is compared with the finite element simulation results, with an error of 0.43% for quasi-static conditions, a minimum error of 0.17% and a maximum error of −1.41% for impact conditions, in addition to significantly improved accuracy compared to the EC3 model, which indicates that it can effectively capture the behavior of bolted joints under impact loading conditions. [ABSTRACT FROM AUTHOR]

Boeing and Airbus developed a special testing procedure to investigate the compressive response of laminates that have been impacted (following standards ASTM D 7137 and DIN 65561). This study focuses on both experimental and numerical analysis of Kevlar plates subjected to compression after impact. To ensure high quality and appropriate mechanical properties, the composite plates were manufactured using autoclaving. The DIN 65561 protocol was followed for all three test systems. Initially, ultrasonic C-scanning was performed on all plates before testing to confirm they were free of any significant defects arising from the manufacturing process. Subsequently, low-energy impact testing was conducted at levels ranging from 0 to 8 Joules. Three specimens were tested at each energy level. After the impact, all specimens underwent ultrasonic C-scanning again to assess the internal delamination damage caused by the impactor. Finally, both pristine and impacted specimens were subjected to compressive testing using the special jig specified in DIN 65561. The compressive impact strength results obtained from these tests were plotted against the delamination area measured by C-scanning. These data were then compared to the results obtained from specimens with artificial damage. Semi-empirical equations were used to fit both sets of curves. The same procedure (impact testing, C-scanning, and data analysis) was repeated to investigate the relationship between impact energy and total delamination area. Lastly, finite element modeling was employed to predict the buckling stresses that develop under compression in the impacted systems studied. These modeling approaches have demonstrated good accuracy in reproducing experimental results for CAI tests. [ABSTRACT FROM AUTHOR]

This paper aims to study the low-velocity impact (LVI) response and compression after impact (CAI) performance of carbon/aramid hybrid woven composite laminates employed in marine structures subjected to different energy impacts. The study includes a detailed analysis of the typical LVI responses of hybrid woven composite laminates subjected to the impact with three different energies, as well as a comparative analysis of cracks and internal delamination damage within impact craters. Additionally, the influence of different impact energies on the residual compressive strength of hybrid woven composite laminate is investigated through CAI tests and a comparative analysis of internal delamination damage is also conducted. The results indicate that as the impact energy increases, the impact load and CAI strength show a decreasing trend, while impact displacement and impact dent show an increasing trend. The low-velocity impact tests revealed a range of failure modes observed in the hybrid woven composite laminates. Depending on the specific combination of fiber materials and their orientations, the laminates exhibited different failure mechanisms. Buckling failures were observed in the uppermost composite layers of laminates with intermediate modulus systems. In contrast, laminates with higher modulus systems showed early damage in the form of delamination within the top surface layers. [ABSTRACT FROM AUTHOR]

Composite materials are widely used in industries such as aerospace, automotive, construction, sports equipment, and electronics due to their strength-to-weight ratio, resistance to fatigue and corrosion, and minimal thermal expansion. However, challenges such as high production costs, repair complexity, and difficulties in characterization and modeling exist. Advanced manufacturing techniques, nanocomposites, sustainable composites, multi-functional composites, and bioinspired composites are being explored to address these challenges. Numerical modeling has also advanced to simulate the behavior of composite materials. Sandwich structures, which have high strength-to-weight ratio and durability, find applications in aerospace, automotive, marine, and construction industries. Advanced materials and innovative core materials are being developed for sandwich structures, and automated systems are used for production. Understanding the dynamic behavior of sandwich structures is crucial. The article also provides summaries of various research studies related to composite and sandwich structures, covering topics such as material enhancement, manufacturing techniques, testing methods, and applications. The future of research in this field is expected to focus on multi-material and hybrid structures, advanced manufacturing techniques, durability and environmental resistance, damage detection and structural health monitoring, simulation and modeling, functional and smart materials, and sustainability and recycling. [Extracted from the article]

This research addresses and resolves current challenges in meshless Lagrangian methods for simulating viscoelastic materials. A split-step scheme, or pressure Poisson reformulation of the Navier–Stokes equations, is introduced for incompressible viscoelastic flows in a Lagrangian context. The Lagrangian differencing dynamics (LDD) method, which is a thoroughly validated Lagrangian method for Newtonian and non-Newtonian incompressible flows, is extended to solve the introduced split-step scheme to simulate viscoelastic flows based on the Oldroyd-B constitutive model. To validate and evaluate the new method's capabilities, the following benchmarks were used: lid-driven cavity flow, droplet impact response, 4:1 planar sudden contraction, and die swelling. These findings highlight the LDD method's effectiveness in accurately simulating viscoelastic flows and capturing large deformations and memory effects. Even though the extra stress was directly modeled without any regularization approach, the method produced stable simulations for high Weissenberg numbers. The stability and performance of the the Lagrangian numerics for complex temporal evolution of material properties and stress responses encourage its use for industrial problems dealing with polymers. [ABSTRACT FROM AUTHOR]

With the help of the high‐speed camera and self‐designed fixture, it was investigated that the effects of the impactors in a variety of shapes on the mechanical behavior and failure mode of carbon fiber‐reinforced polymer (CFRP) tubes with a range of inner diameter during the low‐velocity impact (LVI) of four impact energies. Then, the three‐dimensional digital image correlation (3D‐DIC) system was carried out to monitor the damage evolution of the LVI‐damaged specimens under compressive and flexural loading. In addition, the residual compressive and flexural strength of all kinds of cases were compared and discussed. The results show that the increase in wall thickness can improve the LVI, compression‐after‐impact (CAI), and flexure‐after‐impact performance. The failure mode of compression changes to brittle fracture failure at the impact circumferential region. The CAI strength of the specimen damaged by a flat impactor is 23.89% less than that of a hemispherical one, but there is little difference in flexural loading. Highlights: Mechanical behavior on in & post LVI of CFRP tubes varying wall thickness and impactor.Due to point‐line contact for flat impactor, two peak forces are in the F‐D curves.LVI property and residual strength are improved with the increase of wall thickness.Compressive failure mode is brittle fracture at the impact circumferential area.Flexure‐after‐impact strength mainly depends on the no‐impact surface of tubes. [ABSTRACT FROM AUTHOR]

The paper presents the results of research into the influence of the titanium foil thickness on the impact response of metal-ceramic ZrO2/Ti/ZrO2/Ti composites consisting of nonrigidly joined plane-parallel layers. The difference is shown between the deformation behavior of the metal foils in composites with foil thicknesses of 100, 200, and 500 μm. It is found that an increase in the thickness of reinforcing metal layers leads to a higher structure dispersion in the deformation localization zone. The deformation and fracture features of each layer of the composites are studied in detail. A comparative analysis is made of the structural characteristics of materials before and after impact loading. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced-polylactic acid (CF-PLA) composites nowadays are widely researched alternative structural materials for their potential application in prosthetic and orthotic implants. The present work firstly consolidates the findings on the application of 3D printing in biomedical and allied fields. Fatigue life and impact strength of 3D printed CF-PLA test specimens were determined. The test specimens were fabricated through the fused deposition modeling (FDM) approach at two printing temperatures. The pronounced effect of printing temperature is characterized by the significant change in fatigue life and impact strength of the FDM specimen. The fatigue life at the printing temperature of 240°C was 2.7 times greater than that at 225°C, whereas the impact strength was greater by 5.93%. The microscopy findings revealed increased diffusion and a reduced number of ridges and pores at higher printing temperature testifying that printing temperature prominently controls the durability and impact response of FDM printed parts. [ABSTRACT FROM AUTHOR]

This study aims to assess the hybridization effect on the perforation threshold of Low-Velocity Impact (LVI) in thermoplastic glass composite laminates, incorporating layers of resin-impregnated stainless-steel mesh. Reinforcing methodologies such as hybridization are recently being adopted as a practical approach to increasing the energy-absorbing capacity of polymer composites. In the current paper, a multi-step hot press lamination method has been employed to fabricate the hybrid composite laminates strengthened with stainless-steel mesh layers. Several stacking sequences, metal mesh wire sizes, orientation and position relative to the impactor have been examined under various LVI energies. It was revealed that the LVI penetration energy was increased for the thermoplastic-based composite laminates reinforced with stainless-steel mesh layers. Furthermore, the LVI penetration energy threshold was significantly influenced by the metal mesh wire size, orientation and stacking sequence. Finally, the backlight method capability was assessed to detect the after-impact interlaminar damages. [ABSTRACT FROM AUTHOR]

The impact effects of falling rocks on sand–reinforced concrete slab composite protective structures involve several factors. Among them, the existing codes are unable to consider the effect of rockfall shape and the angle of contact between the rockfall and the object on the impact force as well as the depth of penetration. Based on extensive field investigation, this paper proposes a shape factor to simplify the rockfall into an ellipsoid and determines the shape and dimensions of the rockfall by three-dimensional axis length. Besides, a coupled SPH-FEM numerical calculation model is established and validated through comparison with a large-scale outdoor test of a rockfall impact protection structure. Finally, the effects of rockfall shape and impact angle on the symbolic parameters including impact force, impulse and energy in the impact process are revealed. The findings indicate that the maximum force and displacement of the midpoint of the bottom of the reinforced concrete slab have relative errors within 5.0 % when compared to the model test, confirming the precision of the models discussed in this paper. For the same rockfall, the peak force decreases with the impact angle increasing; taking the same volume of spherical rockfall as the reference, under the same rockfall pattern, the peak impact force and impulse amplification factor decreases with the increase in contact attitude angle. Additionally, the scaling effect becomes more pronounced when the shape factor of the rockfall is smaller; under the same shape factor, the impact depth of the cushion layer is the smallest when the attitude angle is 45°, and the maximum when the impact angle is 90°; the SPH-FEM coupling algorithm could reasonably reproduce the pit-forming process of sand and soil, and it is very effective in simulating the flow effect of soil particles under impact.

Background: In endometrial cancer (EC), preoperative anaemia, thrombocytosis and leucocytosis appear to be associated with worse prognosis. It remains unclear whether these parameters solely reflect tumour aggressiveness, or also impact response to adjuvant treatment. Therefore, our primary aim is to evaluate the prognostic relevance of anaemia, thrombocytosis and leucocytosis on survival in EC. Secondary, to explore their predictive relevance in response to radiotherapy in EC. Methods: A retrospective multicentre cohort study was performed within 10 hospitals. Preoperative haematological parameters were defined as: Anaemia - haemoglobin <7.45 mmol/L (< 12g/Dl), thrombocytosis - platelets >400 x 109 platelets/L, leucocytosis - leukocytes >10 x 109/L. The relationship of haematological parameters with clinicopathological characteristics, ESGO/ESTRO/ESP risk groups and survival were evaluated. Furthermore, the predictive value of haematological parameters was deter- mined on the overall response to adjuvant radiotherapy and for the ESGO/ESTRO/ESP intermediate-risk group solely receiving radiotherapy. Results: A total of 894 patients were included with a median follow-up of 4.5 years. Anaemia was pre- sent in 103 (11.5%), thrombocytosis in 79 (8.8%) and leucocytosis in 114 (12.7%) patients. The presence of anaemia or thrombocytosis was significantly associated with ESGO/ESTRO/ESP high-risk (respectively, P = 0.002 and P = 0.041). In the entire cohort, anaemia remained independently associated with decreased disease-specific survival (HR 2.31, 95% CI (1.19-4.50), P = 0.013) after adjusting for age, the abnormal haematological parameters and ESGO/ESTRO/ESP risk groups. In patients that were treated with adjuvant radiotherapy (n = 239), anaemia was associated with significant reduced 5-year disease-specific and recurrence-free survival (P = 0.005 and P = 0.025, respectively). In ESGO/ESTRO/ESP inter-mediate risk patients that received solely vaginal brachytherapy (n = 74), anaemia was associated with reduced disease-specific survival (P = 0.041). Conclusions: Current data demonstrate the importance of preoperative anaemia as independent prognostic factor in patients with EC. Moreover, anaemia seems to be associated with reduced response to radiotherapy. Prospective validation in a larger study cohort is needed to verify anaemia as predictive biomarker for radiotherapy. [ABSTRACT FROM AUTHOR]

Honeycomb structures have attracted wide attention due to outstanding mechanical properties as promising light material structures. Inspired by nature and artistic design, various honeycombs with different microstructural configurations have been designed for the sake of better mechanical performances and functions. Here, the Miura-origami reentrant honeycomb (MRH) structure integrating reentrant honeycombs (RH) and Miura-origami structures is investigated systematically. Dynamic impact behaviors of the present MRH structure are investigated numerically. The deformation modes and energy absorption capacity of RH and MRH are compared under different impact velocities, including low-velocity, medium-velocity and high-velocity. The results show that the plateau stress and the specific energy absorption(SEA) of MRH is much higher than RH. Moreover, the parametric study indicates that raising the inclined angle will decrease the plateau stress and the absolute value of Poisson'ratio for MRH structures. The specific energy absorption curves increase as the inclined angle of MRH grows up. In addition, the MRH with smaller dihedral angle can absorb much more impact energy and the variation of absorbed energy is proportional to the cell wall thickness of the MRH structure. This work is expected to provide a new thought for designing advanced energy absorption metastructures and achieving superior mechanical performances. [ABSTRACT FROM AUTHOR]

Head impacts are a major concern in contact sports and sports with high-speed mobility due to the prevalence of head trauma events and their dire consequences. Surrogates of human heads are required in laboratory testing to safely explore the efficacy of impact-mitigating mechanisms. This work proposes using polymer additive manufacturing technologies to obtain a substitute for the human skull to be filled with a silicone-based brain surrogate. This assembly was instrumentalized with an Inertial Measurement Unit. Its performance was compared to a standard Hybrid III head form in validation tests using commercial headgear. The tests involved impact velocities in a range centered around 5 m/s. The results show a reasonable homology between the head substitutes, with a disparity in the impact response within 20% between the proposed surrogate and the standard head form. The head surrogate herein developed can be easily adapted to other morphologies and will significantly decrease the cost of the laboratory testing of head protection equipment, all while ensuring the safety of the testing process. [ABSTRACT FROM AUTHOR]

A single-layer and double-layer corrugated core sandwich structure consisting of carbon fibre–reinforced polymer (CFRP) panels and aluminium alloy core layers was designed. Numerical simulations were carried out in HyperMesh/LsDyna, and the simulation results of single-layer and double-layer corrugated sandwich structure were compared with the experimental results to verify the reliability of the proposed numerical model. Compared with the results of single-layer and double-layer corrugated sandwich structure, the superiority of a double-layer corrugated sandwich structure in anti-collision performance is verified. Considering the effects of impact energy and impact position on impact force, energy absorption capacity, and failure mode, a series of low-velocity impact finite element simulations was carried out. It was found that the main failure mode of composite laminates included fibre damage, matrix damage and delamination, and core buckling. At the same impact position, the higher the impact energy, the greater the initial slopes of the contact force-time and absorbed energy-time curves, the higher the peak force, and the larger the energy absorption capacity. Under the same impact energy, when the impactor hit the wave crest of the sandwich structure, the damage to the structure was small; however, the maximum impact force on the structure was large (∼8 kN). [ABSTRACT FROM AUTHOR]

In research concerning the impact resistance characteristics of ship power transmission shaft systems incorporating a high-elasticity coupling, a significant challenge lies in ascertaining the displacement compensation metrics for the high-elasticity coupling. This study constructs a finite element model of the ship power transmission shaft system with an entity equivalent model of the high-elasticity coupling. Utilizing the Dynamic Design Analysis Method (DDAM) and the time-history method, the dynamic responses of the high-elasticity coupling, the propulsion shaft system, and its critical cross-sections under explosive impact loads are analyzed. The findings indicate that the maximum impact displacement of the propulsion shafting system, as calculated by DDAM, is 22.47 mm in the vertical direction at the driven end of the high-elasticity coupling. In contrast, the maximum impact displacement determined by the time-history method is 15.23 mm in the same direction. The study corroborates the precision of the high-elasticity coupling equivalent model establishment methodology and confirms that the entity equivalent model of the power transmission shaft system with a high-elasticity coupling is capable of fulfilling the criteria for a swift evaluation of impact resistance characteristics. This provides theoretical backing for the forecasting of impact resistance performance in ship propulsion shaft systems. [ABSTRACT FROM AUTHOR]

In this paper, low‐velocity impact properties and impact damage responses of a novel type of 3D hybrid auxetic structures made from carbon fiber‐reinforced polymer (CFRP) laminates were investigated experimentally and numerically. The structures were first fabricated with three different rib's width ratios t1/t0, and then impacted with three different impact energies of 30, 40, and 50 J using a drop tower impact system equipped with a cylindrical impactor. The finite element (FE) models were built in ABAQUS/Explicit, and the Hashin criteria were applied to predict the failure of the structures. The contact force histories, energy histories, displacements, and failure modes were compared between the experiment and FE simulation at all three impact energy levels. The failure morphologies and mechanisms were obtained and studied. The impact testing results suggest that the 3D auxetic structure with a higher t1/t0 ratio can lead to higher peak contact force and sustain higher impact energy. The failure of the structure starts from the middle area and propagates to the upper and lower areas. This research provides a better understanding of the impact responses and failure modes of the 3D auxetic lattice structure, which can promote the potential applications of the auxetic materials. Highlights: Drop weight low‐velocity impact responses of 3D novel hybrid auxetic lattice structures are investigated through both experiment and finite element simulation.The effects of structural parameters on the impact performance of the 3D auxetic structures at different impact energy levels are analyzed.The failure morphologies and mechanisms of the 3D auxetic structures are studied. [ABSTRACT FROM AUTHOR]

Highlight Considering the nonlinearity of shear in the mechanics of composite materials, the increase of shear strength when the substrate interface is compressed, and the shear of the matrix itself, the Chang–Chang criterion is improved. The improved Chang–Chang criterion was used to establish a progressive damage model of low‐velocity impact of composites. The low‐velocity impact process of T700/EM134 composite laminates in the energy range from 5 to 10 J was compared by physical tests and finite element simulations, and the calculated impact response curves and material damage were in good agreement with the test results, which proved that the model of the improved criterion was suitable for the damage prediction of low‐velocity impact of composite laminates. Consider various situations in composite material shearing. Improved based on the Chang–Chang criterion. Establishing a progressive damage model for low‐speed impacts. Comparison through physical experiments and finite element simulation. Prove that the improved criterion model is suitable for damage prediction. [ABSTRACT FROM AUTHOR]

For understanding characteristics of polymethylmetacrylate (PMMA) under impact, the damage behavior of PMMA plates with various thicknesses (1.5 to 6.0 mm) subjected to ballistic impacts with various velocities (63 to 180 m/s) is experimentally investigated using a specialized testing apparatus. Moreover, numerical simulations using FEM are conducted for the corresponding experimentally studied cases. Ductile response and brittle tensile failure behavior are considered in the FEM to describe the nonlinear response and the failure mode of the PMMA plates. The numerical simulations effectively describe the shape of cracks and perforations of the PMMA plates for all studied 25 cases, verifying the validity of the numerical model. Although the PMMA plates are generally brittle in the selected range of impact velocity, it was found that these plates exhibit ductile behavior under low-velocity impacts. Moreover, the numerical simulations imply that the kinetic energy loss of the projectile is linearly dependent on the plate thickness, whereas the impact velocity hardly affects this loss. This behavior obtained experimentally and numerically illustrates the usefulness of the PMMA material for the use as a protective layer in many applications involving ballistic (high-velocity) impacts. This study delves into the impact behavior of PMMA plates, offering insights with a range of practical implications. This research positions PMMA as a promising protective material for applications exposed to high-velocity impacts. The comprehensive understanding of failure modes aids in designing resilient PMMA structures. By subjecting PMMA plates of varying thicknesses (1.5 to 6.0 mm) to ballistic impacts at different velocities (63 to 180 m/s), this research reveals a nuanced interplay between ductile and brittle behavior within the material. The study uncovers a ductile response of the PMMA plates under low-velocity impacts, expanding the material's potential use in scenarios with lower impact velocities. Moreover, the linear relationship established between plate thickness and kinetic energy loss of the projectile, independent of the impact velocity, provides a practical basis for designing impact-resistant PMMA structures. The practical applications of the study extend to fields such as architectural glazing, automotive safety, and aerospace engineering, where protective materials play a crucial role in safeguarding against unexpected impacts. In summary, this study empowers practical decision-making by uncovering the PMMA's impact response, thereby contributing to optimized protective solutions across various domains. [ABSTRACT FROM AUTHOR]

In general, the majority of fiber-reinforced polymer composites (FRPs) used in structural applications comprise carbon, glass, and aramid fibers reinforced with epoxy resin, with the occasional utilization of polyester and vinyl ester resins. This study aims to assess the feasibility of utilizing recyclable and sustainable materials to create a resilient composite suitable for structural applications, particularly in scenarios involving low-velocity and high-velocity impact (LVI, HVI) loading. The paper presents a comparative analysis of the performance of E-glass, aramid, and eco-friendly basalt-reinforcing fabrics as reinforcement fibers in both thermosetting (epoxy) and recyclable thermoplastic (Elium©) resins. Given the limited research on Elium composites, especially those incorporating basalt-reinforcing fiber, there is an urgent need to expand the databases of fundamental mechanical properties for these diverse composites. This necessity is exacerbated by the scarcity of the literature regarding their performance under low- and high-velocity impact loadings. The results of this study will demonstrate the potential of basalt-reinforced Elium composite as an effective recyclable and environmentally friendly structural material system for both static and dynamic loading conditions. [ABSTRACT FROM AUTHOR]

The widely used Vawter-Fung (VF) lung tissue constitutive model, originally developed to model respiration, was assessed for applicability to impact human body models (HBMs). A review of the mechanical properties of lung tissue demonstrated existing parameter sets for the VF model encompassed a wide range of stiffness relative to experimental data. Consistent experimental datasets of lung tissue for uniaxial and biaxial tension were identified, and new parameters were fit to the VF model. A thoracic pendulum impact using a contemporary HBM was used to assess existing literature parameter sets, and the new parameters. The VF model parameters presented in this study produced uniaxial and biaxial tension response with improved hyperelastic response compared to experimental data and previously reported parameters. The VF surface tension component did not contribute substantially to the lung response in impact. The proposed VF model parameters were numerically stable for impact simulations and use in HBMs. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, the investigation of damage caused by a spherical steel projectile on the polycarbonate (PC) panels has been undertaken both numerically and experimentally. The material properties are obtained from both static and dynamic tests. High‐velocity impact experiments are performed using a pressure‐based projectile launching system. The effect of panel curvatures and impact locations on the deformation are investigated experimentally. The impact locations are selected as both at the plate center and near the edge of the plate. A validation study is performed by analyzing the impact response of a PC plate as previously presented in the literature and subsequently comparing it with the results obtained. An analysis of the impact behavior of PC panels is carried out through numerical simulations using finite element program (LS‐DYNA). The effect of boundary conditions on the impact response is also investigated numerically. Plastic strains, von Mises stresses, dent depth, and energy absorption are obtained. It is indicated by the results that the deformation behavior of PC panels exhibits a strain rate dependence. Additionally, the deformation behavior is influenced by panel curvatures and boundary conditions, emphasizing the necessity to consider these factors in the design of structures, such as canopies made of PC panels. Highlights: Provides a comprehensive understanding of polycarbonate behavior.Emphasizes the influence of impact locations and panel curvatures.Dent depth and stress rise with panel curvature, crucial for design considerations.Emphasizes the significance of strain rate and boundary condition in design. [ABSTRACT FROM AUTHOR]

Graphene aerogel (GA), as a novel solid material, has shown great potential in engineering applications due to its unique mechanical properties. In this study, the mechanical performance of GA under high-velocity projectile impacts is thoroughly investigated using full-atomic molecular dynamics (MD) simulations. The study results show that the porous structure and density are key factors determining the mechanical response of GA under impact loading. Specifically, the impact-induced penetration of the projectile leads to the collapse of the pore structure, causing stretching and subsequent rupture of covalent bonds in graphene sheets. Moreover, the effects of temperature on the mechanical performance of GA have been proven to be minimal, thereby highlighting the mechanical stability of GA over a wide range of temperatures. Finally, the energy absorption density (EAD) and energy absorption efficiency (EAE) metrics are adopted to assess the energy absorption capacity of GA during projectile penetration. The research findings of this work demonstrate the significant potential of GA for energy absorption applications. [ABSTRACT FROM AUTHOR]

This paper examines the response characteristics of a warship's double-layer plates under a secondary near-field explosion after the ship's outer plate has been perforated by shaped metal jets. First, the effectiveness of the Coupled Eulerian–Lagrangian (CEL) method was validated, showing numerical simulations to be well aligned with experimental results. Subsequently, the damage inflicted on the outer plate by metal jets was simplified to a prefabricated orifice, further studying the explosive impact response of double-layer plates under different inter-compartmental water levels and charge distances. Our findings indicated the following: (1) shockwave and bubble pulsation loads are the main causes of deformation in the outer plate; (2) the driving of the outer plate and the flooding water between compartments are the main causes of deformation in the inner plate; and (3) deformation in the outer plate will decrease as the water level in the compartment increases, while deformation in the inner plate will increase with the increasing water level. Consequently, under certain specific damage, the ingress of water into a compartment effectively enhances the explosion resistance of the double-layer plates. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Mechanics is the property of Chinese Journal of Applied Mechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study explores the impact of incorporating Halloysite Nanotubes (HNTs) nanoparticles on the low-velocity impact (LVI) behavior of carbon fiber (CF) laminate epoxy nanocomposites. The objective of this investigation was to observe the effects of different nanotube loadings (0.5 wt.% and 0.7 wt.%) on CF composites and assess their impact resistance. To achieve this, the CF was subjected to Electrophoretic Deposition (EPD) process to introduce the HNTs. Vacuum-assisted Resin Transfer Molding (VaRTM) was employed to fabricate the CF-reinforced epoxy-based laminated nanocomposites with incorporated HNTs. LVI tests were conducted following the ASTM-D-7136 standard, utilizing impact energies of 10 J and 15 J. Subsequently, the damaged areas within the composites were examined using optical microscopy (OM) and scanning electron microscope (SEM). The findings of this investigation revealed a significant enhancement in impact damage resistance with the addition of HNTs. The highest damage resistance and minimal energy absorption were observed at a loading of 0.7 wt.% HNTs. The results reveal that incorporating 0.7 wt.% HNTs substantially reduces delamination damage, influenced by absorbed impact energy. As well it composite underscores enhanced interlaminar bonding through 0.5 wt.% and 0.7 wt.% HNTs modification. Hence, we confidently assert that the addition of HNTs nanoparticles to CF/epoxy composites has considerably influenced the impact response of the nanocomposites. [ABSTRACT FROM AUTHOR]

Ensuring military and police personnel protection is vital for urban security. However, the impact response mechanism of the UHMWPE laminate used in ballistic helmets and vests remains unclear, making it hard to effectively protect the head, chest, and abdomen. This study utilized 3D-DIC technology to analyze UHMWPE laminate's response to 9 mm lead-core pistol bullets traveling at 334.93 m/s. Damage mode and response characteristics were revealed, and an effective numerical calculation method was established that could reveal the energy conversion process. The bullet penetrated by 1.03 mm, causing noticeable fiber traction, resulting in cross-shaped failure due to fiber compression and aggregation. Bulge transitioned from circular to square, initially increasing rapidly, then slowing. Maximum in-plane shear strain occurred at ±45°, with values of 0.0904 and −0.0928. Model accuracy was confirmed by comparing strain distributions. The investigation focused on bullet-laminate interaction and energy conversion. Bullet's kinetic energy is converted into laminate's kinetic and internal energy, with the majority of erosion energy occurring in the first four equivalent sublaminates and the primary energy change in the system occurring at 75 μs in the fourth equivalent sublayer. The results show the damage mode and energy conversion of the laminate, providing theoretical support for understanding the impact response mechanism and improving the efficiency of protective energy absorption. [ABSTRACT FROM AUTHOR]

This study compares the impact damage response and self-healing potential of unstitched and stitched glass/polypropylene (PP) fiber reinforced thermoset composite structures. The novelty of this study is weaving preforms with an intra-ply hybridization of glass and thermoplastic PP fibers and stitching these preforms with a unique stitching pattern by considering the effect of stitching fiber types (PP, Kevlar®, Dyneema®, carbon and silk) on impact damage response and self-healing potential of composites. The mechanical properties of the stitching fiber influenced the composite's behavior against impact and compressive loads. The unstitched composite deflected more than stitched composites under the same impact energy levels due to delaying of delamination via stitching process. The stitching process reduced the damage areas of composites subjected to 30 J and 60 J impact energies by 57 and 86%, respectively. Structural healing significantly decreased the damaged areas of both unstitched and stitched composite structures up to 87%, while it was more effective on stitched composites. The polypropylene melted and accumulated along the path of the stitch pattern, regardless of whether the stitching fiber was thermoplastic. Due to the reduced impacted area, compression after impact (CAI) strength retention of the stitched composite materials increased by up to 94%. [ABSTRACT FROM AUTHOR]

Aluminum foam sandwich (AFS) are widely used in energy absorption because of their light weight and excellent energy dissipation capabilities. In this study, energy absorption, deformation modes, and dynamic response of AFS under low-velocity impact are investigated using experimental and numerical approaches. Dynamic impact tests are performed utilizing a drop hammer impact test on AFS with different core densities, face sheet thicknesses, and impact energy. Based on the 3D Voronoi foam model, a full-scale finite element model (FEM) is developed to simulate the mechanical response of AFS under low-velocity impact, and verified by experimental results. The contributions of different AFS components to energy absorption at various impact velocities are further analyzed, along with the effects of face sheet thickness distribution. The results indicate that the performance of the face sheet and core and the impact energy have a remarkable influence on the low-velocity impact response and damage modes of the AFS. The type of structure configuration, "thin top and thick bottom," enables the AFS better play its energy absorption while ensuring the overall light weight. This study provides a reference for the design and optimization of the face sheet thickness of AFS when it is used as an energy-absorbing member and improves their design efficiency. [ABSTRACT FROM AUTHOR]

In this study, oil palm empty fruit bunch (OPEFB)-reinforced composites were subjected to a low-velocity impact test to study their energy absorption characteristics. Two sets of OPEFB-reinforced composite specimens were used, comprising 30:70 and 40:60 fiber/epoxy fractions. One set of specimens was treated with a 3% NaOH solution. The drop impact responses, fragmentation characteristics, energy absorptions, and residual strengths of both sets of specimens were analyzed. Drop impact tests were performed using three different energy levels, namely, 10, 13, and 16 J. In general, the results indicated that all the untreated specimens absorbed higher energy than that of the treated specimens, thus suffering severe surface and structural damage. This result is attributed to the treated specimens providing a better interlocking mechanism between the matrix and fibers and dissipating the impact energy through the impactor. Regarding fiber loading, all the 30:70 fiber/epoxy composites exhibited slightly less energy absorption than the 40:60 fiber/epoxy composites. [ABSTRACT FROM AUTHOR]

When an impactor strikes a layered target, both the impactor and the target experience waves. The waves produced travel and engage in interactions with other waves as well as the interfaces in the impactor-target system. For the impact problems on a layered mediumwith periodic properties and layered elastic media of Goupillaud-type (each layer has the same wave travel time), researchers have presented an analytical solution for stress variation with position and time within the target. However, the solution for an elastic media not satisfying the above conditions is not available in the literature. The present study fills this gap and finds the behaviour of a generalized layered medium to an impact problem. The response of the material at any position inside the layered medium is found by solving the interaction between waves, interfaces, and boundaries. The mass, momentum balance and constitutive relationship are solved to get the exact analytical expressions for particle velocity and stress for each possible wave interaction happening in the impactor and the layered medium. The expressions are utilized in a computer program to study the impact behaviour of a layered media. The code tracks each wave as it travels through the system and identifies those interactions that occur in the shortest time, uses the stress and velocity expression for that interaction, and updates the state of the material. When stress produced at the impact surface is tensile in nature, the impactor and target can be separated. The work can be applied to both finite and semi-infinite impactors and targets, and the layered medium does not necessarily have to be a periodic layered media or a Goupillaud-type medium. [ABSTRACT FROM AUTHOR]

Experimental and simulation studies of the response of bonded‐repaired and scarf‐repaired carbon fiber‐reinforced polymer laminates under the low‐velocity impact (LVI) were carried out. The center‐ and eccentric‐repaired laminates were prepared for experiments. The experimental results verify the validity of the finite element model in terms of the force response and different modes of damage. The effect of impact energy and the variation of repair position on the impact response of the laminate was investigated based on the benchmark model. The bonded repaired laminates have higher peak impact forces and lower energy absorption than the scarf‐repaired laminates; the damage of the bonded repaired laminate is mainly intralaminar damage and delamination damage of the patch; the adhesive of the scarf repair is prone to failure, leading to poor impact resistance. The relative positions of the impact point and the patch determine the impact response of a laminate repaired at different locations. The impact point at the edge of the patch has a detrimental effect on the repaired laminate. The impact point vertical position near the bottom hole edge of the parent plate in the scarf‐repaired case harms the impact resistance of the laminate. Highlights: The low‐velocity impact response of bonded versus scarf‐repaired laminates was compared.Bonding repairs provide superior impact resistance to damaged laminates than scarf repairs.The risk of adhesive failure in scarf repair is significantly higher than in bonded repair.The relative position of the damage (repair) to the impact point critically influences the impact response.Impacts near the edge of the initial damage hole can cause severe damage to scarf‐repaired laminates. [ABSTRACT FROM AUTHOR]

This study investigates the effect of damage interference resulting from impact loads on the mechanical response and impact fatigue life of E‐glass/epoxy composite laminate shells. The analysis involves single impacts at different points to evaluate the impact strength's dependency on boundary conditions. Notably, there is a gradual reduction in both maximum impact force and absorbed energy beyond 10 mm from the centre, towards unconstrained edges, accompanied by an increase in displacement. Specifically, at a distance of 30 mm, the maximum force and absorbed energy register a decrease of 9.4% and 7.9%, respectively, while the displacement rises by 14.5%. The findings reveal that the damage severity decreases as the impact point is closer to the unconstrained edge of the specimen, which can be attributed to a stiffness reduction, which can reach up to 22%. Symmetrically induced pre‐damages exhibit no discernible effect on the subsequent impact response. It is observed that beyond 10 mm from the shell's centre, the number of impacts required to reach puncture increases by 10.5% and 21.1% for distances of 20 and 30 mm, respectively. Furthermore, it is also found that alternating impacts between symmetrical points show no inclination towards a preferential point for puncture. Highlights: The single impact strength's dependents on the boundary conditions.Reduction in both maximum impact force and absorbed energy near the unconstrained edges.Damage severity decreases as the impact point is closer to the unconstrained edges.Symmetrically induced pre‐damages have no discernible effect on the subsequent impact response.Alternating impacts between symmetrical points show no inclination towards a preferential point for puncture. [ABSTRACT FROM AUTHOR]

In present investigation, experimental and numerical approaches were combined to investigate the distance between impact positions (DBIP) effects upon impact response and damage accumulation regarding carbon/glass hybrid laminates with multiple low‐velocity impacts. Force/energy‐time curves as well as force‐displacement curves with respect to the laminates with three various impact energies at four different impact positions were obtained from experiment data. Then C‐scans were made to quantify the damage of all the impacted specimens. Additionally, an integrated multi‐impact model was created considering both interlaminar delamination and intralaminar damage. Continuum damage mechanics model (CDM) was developed to calculate the impact resistance regarding laminates under various impact loadings with high efficiency. The simulation and experimental results agreed well. Moreover, the qualitative effects of impact positions on the laminates' mechanical responses were summarized utilizing predictive model that validated. Highlights: The effect of the DBIP on the impact response and damage accumulation of carbon/glass hybrid laminates subjected to multiple low‐velocity impacts was studied.An integrated multi‐impact model was developed to predict the impact resistance of laminates under various impact loadings with high efficiency.The qualitative effects of impact positions on the laminates' mechanical responses were summarized using a validated predictive model. [ABSTRACT FROM AUTHOR]

This article aims to investigate the dynamic behavior of high-performance multi-axial warp-knitted flexible composite materials under low-velocity impact tests through experiments and numerical simulations. In this paper, high-performance multi-axial warp-knitted flexible composites were prepared. Three different preparation processes, 175°C-5 min, 185°C-10 min, and 195°C-15 min, were designed for the multi-axial warp-knitted flexible composites. Studied the impact response of different preparation processes, initial impact energy, and punch shapes and diameters on materials. The results showed that the flexible composites prepared by various processes exhibit the same impact response curves in the impact resistance process, while the damage morphology and failure modes of the samples are different. Different initial impact energies caused multiple failure modes in the samples. The material showed penetration damage at high energy impacts and permanent depression damage at low energies. For different punch shapes, the impact resistance of materials to hemispherical punches is better than that of cylindrical punches. Numerical simulations were carried out using the finite element software ABAQUS. The custom material subroutine (VUMAT) based on the Hashin damage criterion model was implemented in the finite element program. The experimental and numerical simulation results agree regarding impact response characteristics. This paper analyzes the composite damage shapes, crack extensions caused by low-velocity impact tests and finite element simulation on multi-axial warp-knitted flexible composites. It provides a valuable reference for failure and structural optimization of multi-axial warp-knitted flexible composites for architectural applications. [ABSTRACT FROM AUTHOR]

Curved panels are used for ships due to complex situations that can be under external loading. So, it is very important to know about the stability related to the curved system under Low-Velocity Impact (LVI). To improve the stability of this kind of structure, graphene oxide powders (GOPs) are added to its matrix. In addition, the contact force between the impactor and shell is evaluated by implementing Hertz contact theory. So, in the current work, as a first attempt, energy absorption and low-velocity impact response of functionally graded graphene oxide powders-reinforced nanocomposite panel on the viscoelastic substrate is presented. Higher-order shear deformation theory (HSDT), which has twelve factors, is employed to determine the displacement domains. Also, the minimum potential energy technique is designated to obtain the governing equations and end conditions. Moreover, Galerkin and Newmark methods are chosen to solve the relationships. The governing equations related to the curved system under external excitation aimed at achieving the LVI and dynamic outputs are determined by the connection of Galerkin and Newmark methods. The uniqueness of this research is considering the impacts associated with HSDT and various Boundary Conditions (BCs) in addition to considering FG oxide powder reinforcement. The outputs segment displays the effects related to the BCs, the radius of the impactor, mass, and velocity, as well as the weight fraction related to the GOPs on contact force, the indentation, and the indenter velocity. [ABSTRACT FROM AUTHOR]

This study investigates the effects of baffles and various other design changes on a partially filled fuel tank subjected to high-velocity projectile impact. Modelling of the tank filled with water is done using ANSYS software. The Eulerian domain is used to analyse water, whereas the Lagrangian domain is used to assess the tank and bullet. The developed finite element model is verified with available results in the literature. The effect of design parameters like edge fillet, number of baffles, thickness of baffles, orientation of baffles, height of baffles, position of the projectile and projectile speed on the impact responses of the fuel tank is studied. From the analysis results, it could be observed that the edge fillet provided the minimum stress due to the lower stress concentration on the fuel tank, but it was not effective in decreasing the velocity of the projectile. Therefore, the baffles are introduced inside the fuel tanks, which are highly effective in reducing the velocity and generating huge stress on the tanks. The velocity and position of the projectiles are also varied to understand their effect on the fuel tank. [ABSTRACT FROM AUTHOR]

In order to study the vulnerability of 1,1'-dihydroxy-5,5'-bistetrazole dihydroxylamine salt (HATO) based explosives, a comparative study of the bullet impact vulnerable characteristics of HATO-based explosives and HMX-based explosives were carried out by using the 12.7 mm bullet impact test method of the 700-group of the Military Mixed Explosives Formulation and Performance Test Methods. The results of the study indicate that due to the friction and impact sensitivities of the HATO and the HMX explosives are similar, and the bullet impact response degree and the safety performance of the HATO-based explosives and HMX-based explosives is equivalent too. [ABSTRACT FROM AUTHOR]