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There has been a growing surge of interest in examining the shock response of titanium alloys, owing to their considerable potential for military applications. The present study aims to reveal the influence of phase stability on the shock-induced mechanical response and substructure evolution of a metastable β titanium alloy, namely, Ti-17. This investigation included extensive work, such as plate impact tests, quasi-static reloading compression tests, and electron microscope analyses. The microstructural evaluations following the shock-wave loading unveil planar slip as the prevailing deformation mechanism in Ti-17 with a bimodal microstructure with stable α and β phases. However, when the shock stress exceeds 10 GPa, the activation of { 10 1 ¯ 1 } α nano-sized twins was observed, leading to improved reloading ductility. This implies a novel strategy to achieve excellent strength-plasticity compatibility in titanium alloys through appropriate shock-wave loading. Conversely, in Ti-17 with an equiaxed β microstructure, the metastability of the β phase leads to the activation of shock-induced α″ martensite, shock-induced ω, and planar slip. Two distinct forms of interaction involving the α″ laths, i.e., shear and truncation, were also observed. Phase stability greatly influences substructure evolution, which ultimately controls the reloading mechanical properties of the postshock Ti-17 alloy. [ABSTRACT FROM AUTHOR]

Ceramic materials are widely used in armor or protective structures, providing weight saving at equivalent performance in comparison to their steel counterparts. Plate-impact experiments are commonly used to investigate the dynamic behavior of ceramics under compressive loading. Using the particle velocity measured at the back of the target, some mechanical properties such as the Hugoniot elastic limit (HEL) as well as the Hugoniot curve of the material can be deduced. Nevertheless, these tests do not provide a direct measurement of the plastic hardening (post-HEL) behavior of the target. In the present work, an experimental shockless plate-impact configuration was developed and implemented to conduct a Lagrangian analysis. This configuration relies on the use of a wavy-machined flyer plate impacting a target made of a buffer, two ceramic plates of different thicknesses, and two window plates as backing. First, the use of wavy flyer plates to generate a loading ramp was validated by considering the impact of the wavy-machined flyer plate against a target, both made of 316L steel. A numerical analysis of this test was developed to confirm the pulse-shaping effect observed experimentally. Next, a ceramic, F99.7 alumina was subjected to the shockless plate impact test in Lagrangian configuration considering the same steel as a buffer and flyer plate material. These tests coupled with Lagrangian analysis enable the curve of axial-stress vs axial-strain beyond the isentropic elastic limit (IEL) to be deduced. The experimental data allow identifying the parameters of an elastoplastic with strain-hardening model to describe the behavior of the tested alumina. [ABSTRACT FROM AUTHOR]

Anatase type TiO 2 has garnered significant attention due to its potent oxidation capacity, stability, photoinduced superhydrophilicity and self-cleaning performance. However, there are few reports on the preparation of robust TiO 2 films on substrates with a low glass transition temperature. In this work, SiO 2 /TiO 2 films were fabricated on PE substrates using a simple dip-coating technique. The coated PE films exhibited a maximum transmittance of 86 % and an average transmittance of 85 % in the visible region. The composite films demonstrated remarkable photoinduced superhydrophilicity, antifogging characteristics, and excellent photocatalytic performance. The film showed superhydrophilicity under UV light or xenon lamp illumination, and remained superhydrophilicity after it was placed outdoors for 310 days. In addition, the prepared films also had excellent mechanical properties, and their superhydrophilicity remained unaffected even after 200 cycles of bending, 80 cycles of rolling, and 50 mL water impact test. The preparation method may open a new avenue to the application of TiO 2 films on many substrates that are vulnerable to high temperature processes. [Display omitted] • In this work, SiO 2 /TiO 2 films were fabricated on PE substrates using a simple dip-coating technique. • The composite films demonstrated remarkable photoinduced superhydrophilicity, antifogging characteristics, and excellent photocatalytic performance. • The prepared films also had excellent mechanical properties, and their superhydrophilicity remained unaffected even after 200 cycles of bending, 80 cycles of rolling, and 50 mL water impact test. [ABSTRACT FROM AUTHOR]

Highlights The outstanding mechanical performance and flowability of unidirectionally arrayed chopped strands (UACSs) give them an advantage in the manufacture of engineering structures with complex geometry. For the application of practical structures, the impact responses and damage evolution of material under low‐velocity impact must be investigated in advance. In this study, UACS laminates and continuous carbon fiber laminates with a stacking sequence of [0/90]4s and a thickness of 2 mm were fabricated for low‐velocity impact tests at 7, 11, 15, and 20 J. The impact responses and postimpact intralaminar damage area were analyzed according to the experimental results, including impact load responses and ultrasound C‐scan inspections. Moreover, to predict the damage evolution of the internal structure, the 3D finite element models were constructed in ABAQUS using a progressive damage model (PDM) through a user‐material subroutine VUMAT. Compared with continuous carbon fiber laminates, the dissipated energy of UACS laminates increases by approximately 10.64% and 57.37% for the 15 and 20 J, respectively. However, the intralaminar damage area of UACS laminates decreased by 29.96% and 28.16% at 15 and 20 J, respectively, since the discontinuous slits in UACS laminates can guide damage paths and suppress damage propagation. The regularly arrayed short fiber reinforced composite was studied. Revealed the low‐velocity impact responses and predicted the damage evolution. UACS and CFRP laminates have comparable impact performance. Illustrated the slits design can suppress the damage to a relatively small area. [ABSTRACT FROM AUTHOR]

An improved melt foaming method is employed to fabricate composite aluminum foam tubes (CAFTs) with varying diameter ratios, achieving metallurgical bonding between the aluminum foam and aluminum tubes. Based on the structural characteristics of aluminum foam‐filled tubes and traditional numerical formula for calculating the energy absorption properties of metal foams, a new calculation formula is proposed to accurately evaluate energy absorption performance of CAFTs under axial load, enabling more precise numerical calculation of total energy absorption. Furthermore, drop weight impact tests and finite element simulations are conducted to investigate the axial impact performance and deformation mechanism of CAFTs. The influence of diameter ratio on crashworthiness and energy absorption performance is also analyzed. As the diameter ratios decrease, both the impact resistance and total energy absorption of CAFTs increase, while the degree of tube damage gradually decreases. Moreover, finite element simulation results demonstrate that metallurgical combination between aluminum foam and aluminum tubes effectively transfers stress to thin‐walled tubes with better load‐bearing performance, preventing concentrated collapse of aluminum foam core. Additionally, the presence of aluminum foam provides robust restraint against deformation or rupture in thin‐walled tubes. [ABSTRACT FROM AUTHOR]

As a main functional component of rock sheds in rockfall protection projects, traditional sand cushions have shortcomings such as heavy weight and weak buffering capacity. EPS bead-sand cushion can effectively solve these problems, but its buffering mechanism has not been fully revealed. In this study, a series of impact tests were carried out to investigate the performance of EPS bead-sand cushions with different EPS bead contents, and the evolutions of rockfall impact force, penetration depth, earth pressure, and slab vibration under single impact and multiple impacts were comparatively analyzed. The results show that with the addition of EPS beads, the maximum impact force, the peak earth pressure, and the vibration acceleration are significantly reduced. However, the cushion with high EPS bead content is at risk of being penetrated under high energy or multiple impacts, leading to excessive concentration of impact stresses. Furthermore, the EPS beads can alleviate the hardening of the sand cushion under impact through their deformation coordination, but excessive penetration should be prevented in the design of EPS bead-sand cushions. On this basis, combined with traditional sand cushion design theory, an estimation method for the maximum impact force applicable to EPS bead-sand cushion was proposed. The research results can provide a reference for the design and optimization of cushions in actual projects. [ABSTRACT FROM AUTHOR]

Background: Migraine headache is a major public health problem. Routine medications for migraine treatment are not useful in treating all patients and may have some side effects. The present study aimed to investigate the effect of vitamin D and probiotic co-supplementation on clinical characteristics of migraine, daily functioning, mental health outcomes, and serum levels of high-sensitivity C-reactive protein (hs-CRP). Methods: In this randomized, triple-blinded, placebo-controlled trial, patients aged 18 to 55 years diagnosed with migraine based on the International Classification of Headache Disorders-3 (ICHD-3) were randomized to either vitamin D (50,000 IU every 2 weeks) plus probiotic (4.5 × 1011 CFU per day) or placebo for 12 weeks. The Headache Impact Test (HIT-6) and Depression, Anxiety, and Stress Scale (DASS) questionnaires were administered to patients at baseline and after 12 weeks. In addition, the frequency, duration, and severity of migraine headaches per month were assessed using a self-administered 30-day headache diary at baseline and the end of the intervention. Anthropometric indices, blood pressure, and serum levels of 25-hydroxy vitamin D and hs-CRP were also examined at first and the end of the study. Results: Seventy-two migraine patients with a mean age of 37.46 ± 8.32 years were included in this trial. Probiotic and vitamin D co-supplementation compared to placebo resulted in a significant increase in serum levels of vitamin D (+ 12.86 ± 1.64 vs. + 1.12 ± 0.80 ng/mL, P < 0.001). The between-group analysis in the adjusted model showed a significantly greater reduction in migraine headache frequency (− 3.17 ± 0.84 vs. − 1.25 ± 0.34; P = 0.031) and severity (− 1.55 ± 0.35 vs. + 0.67 ± 0.29; P = 0.017) in the probiotic and vitamin D group than the placebo group. No significant difference was found between the two arms of the intervention regarding the change in headache duration, hs-CRP, scores of DASS, and HIT-6 questionnaires (P > 0.05). Conclusions: This trial showed that probiotic and vitamin D co-supplementation for 12 weeks has beneficial effects on migraine headache characteristics. Further research is needed to confirm this finding. [ABSTRACT FROM AUTHOR]

This research paper aims to optimize the TIG welding parameters to join dissimilar metals of AA5083 and AA7075 using the Taguchi technique. The TIG welding current and root gap of butt geometry configuration are considered input parameters, and welding characteristics such as tensile strength, 0.2% of yield strength, hardness, and impact energy are output responses. The base metals are joined according to the Taguchi L-09 design of experiments. The welded samples were inspected using the X-ray radiography method for internal defects. Tensile properties, hardness number, and impact energy of different welding coupons were evaluated by conducting the uni-axial testing, a Brinell hardness test, and an Izod impact test, respectively. A better weld strength of 224 MPa was observed at 210 A welding current, and the root gap of 1.5 mm was maintained. Better hardness and impact energy values were observed when the root gap of 1.5 mm and welding current of 220 A were maintained. The root gap is the primary factor influencing tensile strength enhancement, which accounts for 44.78% of the effect, followed by 40.5% welding current. Root gap is the parameter that affects the tensile properties, hardness number, and impact toughness the most. The findings of this paper suggest the optimal parameters for welding AA5083 and AA7075 dissimilar base metals, which are suitable for complex structures requiring both durability and resistance to harsh environments. [ABSTRACT FROM AUTHOR]

The use of natural fibers has been suggested by researchers for the purpose of promoting environmental sustainability. In this work, hybrid composites made of coir and banana fibers were fabricated by using both green resin and epoxy resin in the preparation of composites. Soybean oil is used in this work as the eco‐friendly resin. To determine the mechanical characteristics of the composites, a number of experiments were carried out including tensile, compression, hardness and impact tests. In addition, testing was done on the sound absorption qualities. Composites composed of green resins exhibit superior environmentally friendly characteristics and mechanical robustness in comparison to composites based on epoxy resin. The tensile strength of the hybrid composites exhibited superior performance compared to other hybrid composites. The additional mechanical qualities of the hybrid composites are noteworthy and serve as a driving force to pursue the development of specific applications. Highlights: Hybrid composites exhibit superior mechanical properties.The use of natural resin‐based composites is limited.There is a potential scope for developing hybrid composites using natural fibers and resin for acoustic applications. [ABSTRACT FROM AUTHOR]

The assessment of energy absorption behavior has a vital role in determining suitability of lightweight composites for impact protection applications. This study focuses on evaluating the energy absorption characteristics of cenosphere reinforced epoxy syntactic foam core and jute epoxy facesheet sandwich composite subjected to low velocity impact. The syntactic foam is composed of lightweight cenospheres embedded within an epoxy matrix, resulting in a high‐strength and lightweight composite material. Low velocity impact tests were conducted using a drop tower apparatus to simulate realistic impact conditions. The impact force, energy absorption and damage mitigation of the syntactic foam specimens with varied weight percentage of Cenosphere (0%, 10%, 20% and 30%) were measured and analyzed to assess the energy absorption behavior. The gradation revealed that the weight of top layer when compared to bottom layer is 50.49%, 70.23% and 95.74% less in syntactic foam core with 10, 20 and 30 wt% Cenosphere respectively, indicating gradation. The study demonstrates that the addition of Cenosphere up to 20 wt% enhances the energy absorption capacity of the sandwich composites by 59.37%–93.44% compared to sandwich without Cenosphere reinforced core. However, beyond this threshold, a decline in energy absorption is observed when subjected to low‐velocity impact (LVI). Fractography analysis demonstrates that the incorporation of Cenosphere induces a rough fracture surface with deep river‐like topography, indicative of greater energy absorption during impact loading. This substantiates the conclusion that Cenosphere‐reinforced syntactic foams exhibit enhanced impact resistance, making them promising materials for structures subjected to low‐velocity impact events. Highlights: Development of functionally graded core sandwich composite for low velocity impact applications.Assessing the performance of developed composites under low velocity impact loading.Determining the optimal weight percentage of cenospshere in functionally graded core.Studying the fractography of developed sandwich composites.Corelation between experimental and finite element studies. [ABSTRACT FROM AUTHOR]

Purpose: Medication overuse headache (MOH) is a chronic headache caused by regular overuse of medications. OnabotulinumtoxinA (BoNTA) is used for preventive treatment of MOH. However, its efficacy and safety remain controversial. Methods: Seven online databases (Cochrane Library, Embase, Medline, PubMed, China National Knowledge Infrastructure, Wanfang data, and Chinese BioMedical Literature Database) were searched for relevant articles published between January 2002 and March 2024. We included randomized controlled trials (RCTs) and cohort studies on the treatment of MOH using BoNTA versus a placebo or other active treatments. Results: We retrieved 487 articles in the database search. Of these, four eligible RCTs were identified after detailed screening. A total of 1,259 patients with MOH (622 patients treated with BoNTA, 607 with placebo, and 30 with topiramate) were included in the four RCTs. We found that BoNTA significantly reduced headache frequency compared with placebo (mean difference, 1.89; 95% confidence interval (CI), 1.11-2.67; I2 = 0%; p < 0.001). There was no significant difference between BoNTA and the placebo in terms of secondary outcomes, which included reductions in acute medication intake (MD, 1.30; 95% CI, -1.18- 3.78; I2 = 0%; p = 0.30), Migraine Disability Assessment questionnaire scores (MIDAS, MD, -4.04; 95% CI, -29.36-21.28; I2 = 0%; p = 0.75), and Headache Impact Test scores (HIT-6, MD, 0.03; 95% CI, -1.77-1.83; I2 = 0%; p = 0.97). BoNTA was more likely to cause adverse events (OR, 1.87; 95% CI, 1.45-2.42; I2 = 0%; p < 0.001) than placebo. Conclusion: The results of this study show that BoNTA reduces headache frequency and is effective for the treatment of MOH. [ABSTRACT FROM AUTHOR]

In this paper, different hybrid propulsion screw structures are analysed based on EDEM-CFD. Firstly, three screw models with different perturbation directions are established to analyse the mixing effect of ordinary screw, axial-disturbed screw and radial-disturbed screw based on EDEM. Then the trends of anti-skid coating volume fraction changes within the three structures are simulated by CFD. Finally, the prototype was prepared and experimented. The results show that the volume fraction inside the radial-disturbed screw is 5 times that of the axial-disturbed screw and 6 times that of the common screw, indicating that the radial-disturbed is more favourable to the mixing of anti-slip coatings. The performance of radial-disturbed screw mixing was found to be higher than that of manual mixing by impact and compression experiments, which verified the correctness of the analysis. [ABSTRACT FROM AUTHOR]

A comparative study of the structural integrity of an opaque recycled poly(ethylene terephthalate) (rPET-O) has been carried out with two types of modified rPET-O by applying reactive extrusion techniques, namely (a) using a multi-epoxide reactive agent (REx-rPET-O) and (b) a 90/10 (wt/wt) rPET-O/polycarbonate (PC) blend. The chemical modifications introduced during reactive extrusion were confirmed using differential scanning calorimetry (DSC) and rheological dynamic analysis (RDA). For the quantification of the fracture parameters, an instrumented pendulum impact testing machine was used using specimens in SENB configuration. The structural modifications generated during reactive extrusion promote an increase of between 16 (REx-rPET-O) and 20% (rPET-O/PC) in the stress-intensity factor (KQ) compared to unmodified rPET-O. The most significant differences between both modifications are registered in the "specific work of fracture" (wf) (alternative parameter to the standardized impact strength), where an increase of 61% is reached for the case of rPET-O/PC and only 11% for REx-rPET-O. This trend can be attributed to the type of reactive modification that is generated, namely chain branching (REx-rPET-O) vs. the generation of a random copolymer "in situ" (rPET-O/PC). This copolymer decreases the crystallization capacity and degree of crystalline perfection of rPET-O, promoting an increase in the critical hydrostatic stress conditions for the generation of crazing and crack propagation. [ABSTRACT FROM AUTHOR]

The effectiveness of repair work relies on whether the interface substrate can achieve sufficient bond strength when subjected to numerous stresses. This study investigated the bond properties of repaired normal concrete (NC-to-NC) elements, including cube, beam, and U-shaped specimens, after undergoing natural fracture due to flexural and tensile stresses. The specimens were repaired using a polyurethane (PU) matrix by gluing the two parts and applying compression, splitting, and drop-weight impact (DWI) tests to evaluate the bond strength properties. The results revealed that the PU matrix effectively repairs NC substrate with adequate bond strength, which exceeds the minimum allowable bond strength specified in the ASTM ACI 546-06 to rehabilitate damage concrete structures. The reference beams exhibit a peak applied load capacity of 15.6 kN with less deflection than the repaired samples. The compressive strength of the NC-to-NC repaired specimens loaded along and parallel to the interface plane revealed a decrease in compressive strength of 47.3% and 31.5% compared to the NC-R samples, respectively. The mean number of blows at the cracking stages appeared nearly equal for reference and repaired NC-to-NC specimens. The reference specimens exhibited an average number of 24 and 31 blows at the initial and failure stages, respectively, which were higher by 9.1% and 5.2% than the NC-to-NC repaired specimens. The PU binder showed promising results in achieving adequate interfacial bond strength under static and impact loads. [ABSTRACT FROM AUTHOR]

Due to their extraordinary qualities, including fire resistance, excellent crashworthiness, low thermal conductivity, permeability, non-toxicity, and reduced density, cellular materials have found extensive use in various engineering applications. This study uses a finite element analysis (FEA) to model the dynamic compressive behaviour of agglomerated cork to ascertain how its material density and stress relaxation behaviour are related. Adding the Mullins effect into the constitutive modelling of impact tests, its rebound phase and subsequent second impact were further examined and simulated. Quasi-static and dynamic compression tests were used to evaluate the mechanical properties of three distinct agglomerated cork composite samples to feed the numerical model. According to the results, agglomerated cork has a significant capacity for elastic rebound, especially under dynamic strain rates, with minimal permanent deformation. For instance, the minimum value of its bounce-back energy is 11.8% of the initial kinetic energy, and its maximum permanent plastic deformation is less than 10%. The material's model simulation adequately depicts the agglomerated cork's response to initial and follow-up impacts by accurately reproducing the material's dynamic compressive behaviour. In terms of innovation, this work stands out since it tackles the rebounding phenomena, which was not previously investigated in this group's prior publication, either numerically or experimentally. Thus, this group has expanded the research on cork materials' attributes. [ABSTRACT FROM AUTHOR]

Currently, scientific studies have are focusing on environmentally friendly solutions, such as the effective use of waste in new green polymeric materials according to circular economy. Waste valorization is the main driving force for upcoming academic research. In this study, the impact of mussel particle size on reinforced biopoly(terphtalate ethylene) (bPET) is investigated. The waste filler was modified using NaOH. The filler content was 10 wt% and the same for all samples. The strength properties of the materials were determined in static tensile, bending and impact tests. The wetting angle was also analyzed for the obtained biocomposites. A low-cycle dynamic test was carried out to determine changes in dissipation energy and to observe the development of relaxation processes. This present study proves that preparation of new biocomposites based on waste mussels is an effective option in waste management. [ABSTRACT FROM AUTHOR]

The surrounding rock stiffness has a significant effect on the impact mechanical properties of rockbolts. In order to study the influence of radial stiffness of surrounding rock on the dynamic characteristics of the end-anchored rockbolt, numerical simulations of drop weight impact tests on the end-anchored rockbolt were conducted using finite element method. The simulation results show that the larger the radial stiffness of the surrounding rock, the larger the value of the absorbed impact energy of end-anchored rockbolt. However, there is an upper limit to the effect of radial stiffness on the dynamic behavior of end-anchored rockbolt, i.e., the value of absorbed impact energy tends to be stabilized when the radial stiffness exceeds 2.91 GPa/mm. In the impact simulation, the fracture position of the bolt bar is affected by both radial stiffness and impact energy. The greater the radial stiffness of the surrounding rock, the further the fracture location is away from the anchorage end. The larger the impact energy is, the closer the fracture location is to the anchorage end. It is important to study and determine the range of fracture location of anchor rods to develop new types of anchor rods and to design the support scheme for the surrounding rock under dynamic loading. Finally, due to the linkage between numerical simulation and indoor tests, the effect of steel pipe wall thickness on the upper and lower limits of the results also provides a theoretical basis for the rationalization of the design of steel pipe wall thickness. The study of dynamic impact fracture location of bolt bar is of great significance for the development and design of new types of rockbolt under dynamic loading. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Focusing on the 3060 Goal, China builds a large energy base in Inner Mongolia. The steel structure facilities are subjected to long-term impacts from hard particles in the desert environment. Damage to the surface coatings of the steel structures resulted in reduced durability, and safety. The impact test of polyurethane coating was carried out by using an automatic ball impactor, the strain field of PU coating under impact load was collected by combining with Digital Image Correlation, the damage degree of PU coating was investigated by using Laser Scanning Confocal Microscopy, and elastic-plastic properties of PU coating were also studied. The results show that at the same impact height, the indentation depth of the substrate was Steel substrate > PU coating-steel substrate bilayer system, indicating that the PU coating played a better role in protecting the steel substrate. The compressive strain area at the impact contact point of the PU coating-steel substrate bilayer system increased with the increase of impact height, and the surface of the coating appeared to have different degrees of cracks and spalling. The dynamic hardness increases and then decreases with the increase of impact height, and the dynamic hardness value is the largest when the impact height is 30 cm. HIGHLIGHTS: The strain field distribution of polyurethane coatings under impact loading was studied in combination with DIC, and the crack extension of polyurethane coatings was analyzed using LSCM. The elastic-plastic characteristics of polyurethane coatings were investigated The research results provide a basis for the preparation of protective coatings for steel structures in special environments [ABSTRACT FROM AUTHOR]

Instrumented impact testing and compression-after-impact testing are important to adequately qualify material behavior and safely design composite structures. However, the stresses to which fiber-reinforced plastic components are typically subjected in practice are not considered in the impact test methods recommended in guidelines or standards. In this paper, a test setup for investigating the impact behavior of composite specimens under plane uniaxial and biaxial preloading is presented. For this purpose, a special test setup consisting of a biaxial testing machine and a specially designed drop-weight tower was developed. The design decisions were derived from existing guidelines and standards with the aim of inducing barely visible impact damage in laminated carbon fiber-reinforced plastic specimens. Several measurement systems have been integrated into the setup to allow comprehensive observation of the impact event and specimen behavior. A feasibility test was performed with biaxially prestressed carbon fiber-reinforced plastic specimens in comparison with unstressed reference tests. The compressive-tensile prestressing resulted in lower maximum contact forces, higher maximum deflections, higher residual deflections and a different damage pattern, which was investigated by light microscopic analysis. Finally, the functionality of the experimental setup is discussed, and the results seem to indicate that the test setup and parameters were properly chosen to investigate the effect of prestresses on the impacts behavior of composite structures, in particular for barely visible subsequent damages. [ABSTRACT FROM AUTHOR]

This study experimentally investigated the wave attenuation coefficient and wave number of the heated granite after water cooling (W-C) and air cooling (A-C) treatments. The granite specimens heated to five temperatures (25 °C, 100 °C, 200 °C, 300 °C and 400 °C) were subjected to the W-C and A-C treatments, respectively. The pendulum impact test was performed on the cooled granite at room temperature to obtain the separated stress pulse. The wave attenuation ratio in the cooled granite was investigated. Propagation coefficients (attenuation coefficient and wave number) were introduced to describe the harmonic wave attenuation in the cooled granite. The effects of W-C and A-C treatments on the attenuation coefficient and wave number were discussed. The results show that the P-wave velocity decreases as temperature increases, while the wave attenuation ratio increases as temperature increases. The P-wave velocity of the granite after the W-C treatment is smaller than that of the granite after the A-C treatment. The wave attenuation ratio, attenuation coefficient and wave number of the stress pulse in the granite after the W-C treatment are larger than those of the stress pulse in the granite after the A-C treatment. The differences of P-wave velocity, wave attenuation ratio, attenuation coefficient and wave number after two cooling treatments increase as temperature increases. [ABSTRACT FROM AUTHOR]

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This study investigates the use of jute cloth epoxy reinforced with microfibers from coconuts and bananas to investigate bio‐inspired composite materials. The development and assessment of the mechanical qualities of two composite types—jute fabric containing 10% banana microfibers and jute fabric containing 10% coconut microfibers—were the main goals. These composites were made for the study, and then they underwent extensive mechanical testing (such as tensile, bending, and impact tests) and scanning electron microscopy (SEM) microstructural examination. Jute cloth, which is renowned for its sustainability, was utilized as the foundation material, and epoxy was utilized as the matrix to improve structural stability. Fibers from bananas and coconuts were included because of their durability and low weight. The findings suggested that, maybe as a result of variations in density, the composite containing 10% coconut fibers performed better mechanically than the one containing banana fibers. These discoveries signify a substantial breakthrough in bio‐inspired materials and have potential uses in sectors looking for environmentally friendly substitutes. This research may help create green composites with improved mechanical properties by deepening our understanding of the interactions between jute, epoxy, and natural fibers. Highlights: Banana and coconut fibers enhance the composite's tensile strength significantly.The material's bending properties show promise for diverse load‐bearing applications.High impact resistance makes the composite viable for impact‐prone environments.SEM analysis confirms homogeneous integration of fibers within the epoxy matrix. [ABSTRACT FROM AUTHOR]

The mechanical, thermal, and morphological characteristics of epoxy resin composites reinforced using repurposed textiles are examined in this work. This study investigates reusing textile waste to produce composite materials using sustainable alternatives. This study shows how epoxy resin may be improved by mixing recycled materials with powdered coconut shells. 10% of the total weight, or the powdered coconut shell, was combined with fabric and epoxy resin in a 2:1 ratio with hardener. After the mixture was put into molds, it was given a 72‐h cure. Two samples were then ready to be tested for their mechanical, morphological, and thermal characteristics. Tensile, bending, impact, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) tests were used to evaluate performance. The force obtained in the tensile test was 1236.705 N, the bending test produced 86.76 N, and the impact test produced 3.33 J. The fabric and resin were found to have strong binding by SEM examination, and the TGA investigation indicated a notable heat absorption capability. The study offers insightful information on improving material performance through sustainable methods, which benefits the building, automobile, and aerospace sectors—industries where durability and environmental responsibility are critical. Highlights: Used textiles enhance epoxy resin in composite materials.Tensile tests reveal structural integrity and longevity.Impact tests show resistance to dynamic loads.TGA and SEM analyses clarify thermal stability and bonding. [ABSTRACT FROM AUTHOR]

Data-driven calibration techniques, consisting of theory-guided feed-forward neural networks with long short-term memory, have previously been developed to find suitable input parameters for the finite element simulation of progressive damage in fibre-reinforced composites subjected to compact tension and compact compression tests. The results of these machine learning-assisted calibration approaches are assessed in a range of virtual open-hole strength tests under tensile and compressive loadings as well as in low velocity impact tests. It is demonstrated that the calibrated material models with bi-linear softening are able to simulate the structural response qualitatively and quantitatively with a maximum error of 9 % with regards to experimentally measured open-hole strength values. Furthermore, the highly efficient models enable the virtual analysis of size effects as well as accurate force simulations in quasi-isotropic laminates under impact loading. [ABSTRACT FROM AUTHOR]

This article analyzes the damage tolerance after impact of an unconventional carbon/epoxy laminate (AS4/8552) of the Double-Double (DD) type tested with different impact energies and compares it to a traditional laminate with equivalent properties. Quadriaxial (QUAD) laminate has stacking sequence [03/90/±45]S and the DD equivalent laminate has stacking sequence [0/-55/0/+55]3T. These materials were subjected to the low velocity impact test (LVI) with three energy levels (30 J, 45 J and 74 J), the uniaxial compression test and the compression after impact (CAI). The objective of this article is to validate whether the proposed DD laminate can be a replacement for the QUAD presented, considering the behavior under impact. In addition to the comparative study, this article also has the objective of evaluating whether it is possible to relate the damage tolerance with the delaminated area, and for this purpose, X-ray computed tomography (CT) was performed, making it possible to measure and locate the damage found in the samples. [ABSTRACT FROM AUTHOR]

This work proposed an approach to multi-component non-metallic materials, namely regular polygonal paper honeycomb sandwich tubes filled with polyethylene (PE) foam, and focused on the influence of drop impact parameters and structural parameters on the deformation characteristics and energy absorption of the filled tubes. Axial drop impact tests were employed to exert drop impact loading on cross-sections of the specimens with a square drop weight. The results showed that the X-direction filled tube (X-DFT) had a higher crushing strength and yield strength than that of the Y-direction filled tube (Y-DFT). As the tubular cross-section edge number of the filled tube increased, the specific energy absorption (SEA) and specific total efficiency (STE) decreased. Under the same axial drop impact loading conditions, the SEA and STE of the X-DFT were superior to those of the Y-DFT. As the edge number of the tubular cross-section or the tubular length ratio increased, the SEA and STE of the filled honeycomb tube decreased significantly. While the impact energy increased, the SEA and STE of the filled tubes increased approximately linearly. This work investigated the influence of drop-impact and structural parameters on deformation characteristics and energy absorption. It is expected to provide supplementary documentation for the advancement of cushion protection technology and the optimization of product structure. [ABSTRACT FROM AUTHOR]

Integrating safety features to cut off excessive current during accidental internal short circuits in Li-ion batteries (LIBs) can reduce the risk of thermal runaway. However, making this concept practical requires overcoming challenges in both material development and scalable manufacturing. Here, we demonstrate the roll-to-roll production of a safety reinforced layer (SRL) on current collectors at a rate of 5 km per day. The SRL, made of molecularly engineered polythiophene (PTh) and carbon additives, interrupts current flow during voltage drops or overheating without adversely affecting battery performance. Impact testing on 3.4-Ah pouch cells shows that the SRL reduces battery explosions from 63% to 10%. This work underscores the potential of integrating material science with manufacturing technology to enhance battery safety. The authors present a scalable method for implementing a thermo-responsive safety reinforced layer (SRL) in batteries, which enables immediate shutdown during internal short circuits and reduces the risk of overheating and explosions. [ABSTRACT FROM AUTHOR]

Background Methods Results Conclusion Short‐lasting unilateral neuralgiform headache attacks (SUNHA) are trigeminal autonomic cephalalgias that feature intense and recurrent paroxysms of pain and autonomic symptoms. Many patients are left with debilitating symptoms despite best‐available treatment. Psychedelics, such as the serotonin 2A partial agonist psilocybin, have shown promise in related disorders such as migraine and cluster headache. In this open‐label phase Ib ascending dose study, we aimed to assess the effects of low‐dose oral psilocybin with psychological support in six to 12 patients with chronic SUNHA. Study objectives were to determine effects on cognition, as well as safety, tolerability, and effects on headache severity and frequency.Oral psilocybin in ascending doses of 5, 7.5, and 10 mg (one dose per session; three dosing sessions in total) were administered. Cognition was assessed via the Cambridge Neuropsychological Tests Automated Battery. Headache attacks were assessed via headache diaries and the six‐item Headache Impact Test (HIT‐6). Subjective dose intensity was assessed via the five‐Dimensional Altered States of Consciousness Questionnaire (5D‐ASC). The study was terminated early due to recruitment difficulties; four patients were enrolled, three of whom were study completers. Post hoc, we undertook a thematic analysis of the applicable free‐text clinical trial notes from the dosing and subsequent visits (n = 22). An inductive method was employed to establish emergent themes.No significant adverse events were recorded. We were unable to collect data as planned on cognitive function during the acute experience due to high ratings of subjective dose intensity (mean 5D‐ASC scores 37.8–45.7). The impact of the headaches remained severe throughout the duration of the trial (HIT‐6 mean scores 64.3–65.7). There were limited effects on headache duration and severity based on the diaries; however, mean daily attack frequency decreased by >50% in two participants at final follow‐up (22.9 to 11.0 and 56.4 to 28.0, respectively). Completing participants and their clinicians recorded “much” (two participants) or “minimal” improvements (one participant) at final follow‐up via the Clinical Global Impression rating scale. Thematic analysis indicated that psychological insights were key features of participants’ experience; these insights included re‐configured relationships to their headache pain.The study met with recruitment difficulties and cognition could not be assessed during the acute experience due to subjective dose intensity, likely mediated in part by expectancy effects. The clinical results provide no conclusive evidence for the use of psilocybin in SUNHA. We suggest that accounting for psychological factors in chronic SUNHA may be an important facet of treatment. [ABSTRACT FROM AUTHOR]

Background Objective Methods Results Conclusion The “interictal burden of migraine” (MIB) is a new concept that encompasses the overall impact of the disease between migraine episodes. However, the factors that contribute to this interictal burden are still unclear.This study aimed to identify explanatory factors of interictal burden in patients with migraine.This prospective cross‐sectional observational including 200 patients with migraine (92% [n = 184] female, with a mean [standard deviation] age of 44.8 [12] years, 53% [n = 106] with chronic migraine) completed a clinical and questionnaire assessment targeting MIB, migraine impact, and depressive and cognitive complaints.More than three‐fourths (76% [n = 152]) of patients had moderate‐to‐severe interictal burden. Higher interictal burden (MIB Scale ≥2) was associated with higher headache frequency (eight vs. 14, p = 0.001) and intensity (headache index score 17.0 vs. 30.0, p = 0.002), higher headache impact (six‐item Headache Impact Test score 59.2 vs. 63.9, p = 0.001), and more subjective memory complaints (Subjective Memory Complaints Questionnaire [SMC] score 9.0 vs. 4.5, p = 0.001), as well as anxiety (Hospital Anxiety and Depression Scale (HADS)‐Anxiety score 5 vs. 10, p < 0.001) and depression symptoms (HADS‐Depression score 5 vs. 8, p < 0.001). Once accounted for these potential explanatory variables, subjective memory complaints and impact of headache during ictal phase remained as individual determinants of the interictal burden, with SMC explaining 15% (odds ratio 1.15, 95% confidence interval 1.03–1.28; p = 0.010) of the interictal burden.This finding highlights the need to consider cognitive complaints as part of the construct of interictal burden of these patients to refine the focus of their management. [ABSTRACT FROM AUTHOR]

Highlights Fiber‐metal laminates (FMLs) are generally regarded as excellent lightweight materials for advanced structure design. To enhance the mechanical properties, the common FMLs can be optimized using carbon fibers. However, the combination of carbon fibers with aluminum induces interfacial challenges. Preventing galvanic corrosion with elastomeric interlayers is an effective solution. The lay‐up configuration greatly effects the impact damage resistance of hybrid CFRP‐elastomer‐metal laminates (HyCEMLs). In this work, micro‐CT scans and optical micrographic inspections on HyCEMLs are conducted after impact tests to ascertain the microstructural origins behind the mechanical performance changes. In addition, finite element models of different HyCEML configurations are built to complement the limited experimental data. The damage mechanisms of HyCEML with different configurations under various impact conditions are further compared. The numerical results suggest that impact energy is a more informative measure in terms of damage mode and size than impact velocity and momentum. Results also indicate that when the thickness for each sub‐laminate of HyCEML is maintained the same, hybrid laminates with aluminum stacked outside is beneficial for delaying the occurrence of matrix cracking and delaminations, and enhances HyCEML's resistance to global deformation. These findings will contribute to engineering hybrid laminates with desired impact performance for lightweight load‐bearing structures. The hybrid laminate with elastomeric interlayers is a forward‐looking solution in impact applications. Impact energy is a more informative measure in terms of assessing the damage mode and extent in HyCEMLs. The influence of stacking sequence on damage mechanisms of HyCEMLs is evaluated. Microstructural origins behind variations of hybrid laminates in the impact resistance are revealed. [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]

This study investigates the hygrothermal aging effect on the tensile and impact behavior of flax/PLA biocomposites. Specimens underwent up to four weeks of conditioning at 40°C in a climate chamber with water. Analysis covered porosity, moisture diffusibility, and transversal microstructure, enabling assessment of tensile strength, tensile modulus, and impact performance in relation to moisture uptake and fiber orientation. The study of tensile properties revealed that at approximately 12% moisture content, stiffness and yield stress decrease, while strength remains constant. Moisture diffusivity is higher in warp and weft yarn directions than the out‐of‐plane direction. Tensile testing at environmental equilibrium moisture reveals greater stiffness in the weft direction, correlated with lower crimp percentage and yarn angle. The main contribution of the paper is the study of the influence of moisture on the impact behavior, the results show that energy absorption capability of flax/PLA biocomposite increases with moisture content. Highlights: Fully biodegradable composite material by heat‐compression molding subjected to hygrothermal aging conditions for up to four weeks.The moisture diffusivity in both the warp and weft yarn directions registered higher values in comparison to the out‐of‐plane direction.Tensile testing at environmental equilibrium moisture revealed that the stiffness in the weft direction presented higher values.At 12% of moisture uptake, the stiffness and yield stress reached their lowest values, while strength remained constant.However, the low‐velocity impact properties of the composites exhibited improvement with moisture. [ABSTRACT FROM AUTHOR]

The 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. [ABSTRACT FROM AUTHOR]

AbstractTo improve the epoxy bonding properties of polyphenylene sulfide (PPS) matrix composites, CK-MMT and K-BF were prepared by modifying montmorillonite (MMT) and basalt fiber (BF) with cetyl trimethyl ammonium bromide (CTAB) and 3-Glycidyloxypropyltrimethoxysilane (KH-560) as the modifiers. CK-MMT/BF/TPU/PPS composites were prepared by injection moulding. The surface properties of the composites were tested and characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), etc. The epoxy bonding and mechanical properties were studied by combining the single-lap-joint tensile shear strength test and notched impact test. The results demonstrated the successful preparation of the modified MMT and BF. With the addition of CK-MMT and K-BF in different ratios, the surface roughness and the contents of polar groups of the composites increased, which could effectively improve the epoxy bonding properties of PPS matrix composites. When the additions of CK-MMT and K-BF were 10 and 25 wt%, respectively, the composites had the best overall properties. It demonstrated a single-lap-joint tensile shear strength was 7.56 MPa, representing a 220.34% increase over that of thermoplastic polyurethane/polyphenylene sulfide (TPU/PPS) and a 477.10% increase over that of pure PPS. [ABSTRACT FROM AUTHOR]

Highlights In this work, the behavior of carbon fiber reinforced polymer composites (CFRPs) interleaved with electrospun veils under low velocity impact (LVI) conditions and extreme environmental temperatures was investigated. 2/2 twill carbon fiber/epoxy laminates were subjected to LVI at three energy levels (10, 20, and 30 J), and three temperatures (−50°C, room temperature, and 100°C). Two interleaved configurations were explored (six veils placed symmetrically with respect to the middle plane of the laminate and with respect to the external layers of the laminate). Particularly at room temperature and up to 20 J, nanofibrous interlayers effectively reduced localized deformation (by about 13.0%) and delamination (by about 12.2%) when positioned in the outer ply interleaved configuration compared to the reference laminate. At 100°C, this effect is maintained at 10 J, preventing an increase in the delaminated area. At −50°C and 10 J, the promotion of delamination prevented back surface fiber failure. Regarding post‐impact flexural properties, the presence of nanoveils ensured superior mechanical properties compared to the corresponding reference laminate impacted at the same conditions, demonstrating their efficacy in enhancing the damage tolerance of the overall laminate. Electrospun veils were interleaved in 20 layers of 2/2 twill carbon/epoxy laminate. Three configurations were tested under LVI at 10 J, 20 J, 30 J, and −50°C, RT, and 100°C. Observed damage modes include delamination, indentation, and back surface fiber cracks. Veils symmetrically placed in external layers limit delamination at 20 J (RT) and 10 J (100°C). Electrospun veils enhanced CFRP bending and residual post‐impact properties at RT and 100°C. [ABSTRACT FROM AUTHOR]

AbstractIn this work low and high velocity impact tests were conducted on steel plates with and without polyurea coating. A numerical modeling framework was developed and validated with these experimental results. Additional numerical simulations were carried out to generate more datapoints of residual velocity and ballistic limit under different impact conditions. Using these datapoints, analytical models were developed through which the position, the critical areal density and critical thickness of polyurea coating were determined. These findings will be very useful in designing efficient armor protection systems using polyurea coated layered materials. [ABSTRACT FROM AUTHOR]

Background and Purpose Methods Results Conclusions Fremanezumab, a monoclonal antibody targeting the calcitonin gene‐related peptide for migraine prevention, is available in monthly (225 mg) and quarterly (675 mg) doses. Previous studies showed efficacy and safety for both regimens, but a real‐life comparison is lacking. This study aimed to compare the effectiveness and safety of monthly and quarterly fremanezumab in a real‐life setting.This Italian, prospective, multicenter study enrolled 95 migraine patients. During a 3‐month treatment period, patients received either monthly or quarterly fremanezumab (49 monthly, 46 quarterly). A 6‐month treatment period involved 79 patients (43 monthly, 36 quarterly). Monthly headache (MHD) and migraine days (MMD), number of days (AMD) and pills (AMP) of acute medication intake, and Headache Impact Test (HIT‐6), Migraine Disability Assessment (MIDAS) test, and Numeric Rating Scale (NRS) scores were recorded at baseline and after 3 and 6 months of treatment. Adverse events (AEs), responder rates, and medication overuse were also investigated.Both monthly and quarterly treatments led to significant reductions in MMD, MHD, AMP, AMD, HIT‐6, MIDAS, and NRS scores after 3 and 6 months. The monthly regimen exhibited a slightly greater reduction in MMD and MHD after the first quarter, with no significant difference observed after 6 months. The most common AE was transient injection‐site reaction, without between‐group differences. Responder rates and resolution of medication overuse did not significantly differ between the groups.Both monthly and quarterly regimens were effective and safe, with a tendency for an advantage of the monthly regimen only in the first quarter of treatment. [ABSTRACT FROM AUTHOR]

With the increasingly emerging traffic intersection form of high-speed railways passing underneath integrated transport terminals, the ground vibration induced by trains running on underground high-speed railways has attracted extensive attention. In combination with the engineering example of a high-speed railway in construction passing underneath an airport, the wheel-drop impact test in the high-speed railway tunnel was designed to obtain the vibration characteristics of surrounding soil. The vehicle-track-tunnel-ground semi-analytical three-dimensional model was established to determine the initial dynamic load condition of the vehicle loads. The amplitude-frequency characteristic and transmission law of the ground vibration induced by trains running on underground high-speed railways were predicted and analyzed. The influences of different operation conditions, track parameters, and tunnel burial depths were compared. The research results show that the ground vibration obtained through the wheel-drop test is greatly attenuated within 10 m from the track centerline, with an attenuation rate up to 70%. The vertical vibration amplitude is obviously larger than that of the other two directions. The lateral ground vibration amplitude is the smallest with the slowest vibration attenuation speed. When the high-speed train passes through at the speed of 350 km/h, the vertical and lateral vibration levels of the ground surface within 80 m range are 20∼80 dB and 43∼72 dB, respectively. The maximum attenuation coefficient of Z-vibration level reaches 0.276 dB/m. For each increase of 50 km/h of the train speed, the Z-vibration level of the ground increases by about 2 dB. The smaller fastener stiffness leads to the greater ground vibration within 20∼50 Hz. The ground vibration level is positively correlated with the fastener stiffness above 79 Hz. When the burial depth of the tunnel is greater than 14 m, the burial depth of the tunnel has little effect on the change of the Z-vibration level of the ground. [ABSTRACT FROM AUTHOR]

The emergence of additive manufacturing has enabled scientists to efficiently construct complex geometries, facilitating the development of novel, high-impact energy-absorbing structures suitable for a wide range of industrial applications. The present study conducted flexural and impact test to quantitatively assess the energy absorption capabilities of polymer composites fabricated through fused filament fabrication. Specifically, the polymer composites investigated were multi-walled carbon nanotubes reinforced poly-lactic acid, carbon fibre reinforced poly-ethylene terephthalate glycol, and carbon fibre reinforced poly-lactic acid. The investigation also examined the influence of different infill patterns and nozzle hole diameters on the polymer composites. The investigation depicts that by altering the process parameters, the flexural strength is improved from 21.079 MPa to 70.653 MPa by 235.18%. The experimental study of impact specimens utilising the Izod impact test demonstrates that the rectilinear infill pattern and a nozzle hole diameter of 0.6 mm result in the highest energy absorption of 37.76 kJ/m2 for carbon fibre reinforced poly-lactic acid. The study revealed that the energy absorption of the specimens was significantly influenced by both the independent and interaction effects of process variables. The application of the fused filament fabrication demonstrates an improved energy absorption, making it suitable for manufacturing of vehicle and aircraft components. [ABSTRACT FROM AUTHOR]

The development of impact-resistant composite materials for protective applications such as helmet and body armor has attracted considerable attention. In this study, a novel aramid fiber-woven thermoplastic-epoxy composite was developed. Furthermore, three types of woven textiles, namely three-dimensional (3D) orthogonal-woven (3DOW), 3D angle-interlock woven (3DAIW), and two-dimensional plain-woven (2DPW) textiles, were used as reinforcement structures. To study the effect of the woven structure, impact energy, and damage repairment on impact-resistance performance of these composites, low-velocity drop-weight impact tests with various impact scenarios, such as single-impact, repeated-impact, as well as multiple-impact with hot-press damage repairment, were conducted. The results revealed that the woven structure exhibited an obvious effect on the composite impact-resistance performance and failure modes when subjected to specific impact scenarios. For the single-impact scenario, especially under high impact energy levels (10 and 20 J), the 3DOW structure exhibited superior impact-resistance performance as well as damage tolerance, followed by 3DAIW and 2DPW structures. Furthermore, 3DOW achieved superior impact-resistance to the other two structures for the 10-J repeated-impact scenario. The 3DAIW structure, in which debonding or delamination as well as severe resin cracks dominated, achieved superior impact-resistance to multiple impacts with damage repairment. [ABSTRACT FROM AUTHOR]

A four-point flexure after impact test method has been developed to assess the damage tolerance of sandwich structures under flexural loading. This test method, recently standardized as standard practice ASTM D8388 by ASTM International, is designed for use with sandwich specimens that have been impact damaged per ASTM D7766. The test method utilizes a four-point flexure fixture to test specimens using the methodology from ASTM D7249, along with modifications specified in the practice. The sandwich configurations investigated consisted of carbon/epoxy facesheets with a Nomex® honeycomb core. Mechanical testing was conducted to evaluate the proposed specimen design, fixturing, and test procedure. Finite element analysis was used to finalize the specimen sizing. [ABSTRACT FROM AUTHOR]

This study investigated the thermal and mechanical properties of polyurethane foam (PUF) sandwich panels reinforced with varying amounts of clay nanoparticles (0, 0.5, 1 and 2 wt%) fabricated using the compression molding process. However, these composites were fixed to cores with a honeycomb structure. The morphology of PUF sandwich panels reinforced with clay nanoparticles was examined by scanning electron microscopy (SEM). The presence of clay nanoparticles in the honeycomb structure let to a reduction in cell size and an increase in the number of cells per unit volume. The impact of clay nanoparticles on the thermal properties of PUF reinforced with clay nanoparticles was investigated using thermogravimetric and dynamic mechanical thermal analysis (DMTA). The results indicated that the incorporation of clay nanoparticles as reinforcement enhanced the thermal properties of the PUF sandwich panel samples. Mechanical characterization technique including compression, three-point bending and drop weight impact tests displayed that the PUF reinforced with 1 wt% clay nanoparticles exhibited the most significant improvement in mechanical properties. [ABSTRACT FROM AUTHOR]

The vibration pretreatment–microwave curing process can achieve high-quality molding under low-pressure conditions and is widely used in the curing of resin-based composites. This study investigated the effects of the vibration pretreatment process parameters on the void content and the fiber weight fraction of T700/TRE231; specifically, their influence on the interlaminar shear strength and impact strength of the composite. Initially, an orthogonal experimental design was employed with interlaminar shear strength as the optimization target, where vibration acceleration was determined as the primary factor and dwell time as the secondary factor. Concurrently, thermogravimetric analysis (TGA) was performed based on process parameters that corresponded to the extremum of interlaminar shear strength, revealing a 2.17% difference in fiber weight fraction among specimens with varying parameters, indicating a minimal effect of fiber weight fraction on mechanical properties. Optical digital microscope (ODM) analysis identified interlaminar large-size voids in specimens treated with vibration energy of 5 g and 15 g, while specimens subjected to a vibration energy of 10 g exhibited numerous small-sized voids within layers, suggesting that vibration acceleration influences void escape pathways. Finally, impact testing revealed the effect of the vibration pretreatment process parameters on the impact strength, implying a positive correlation between interlaminar shear strength and impact strength. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic led to a proliferation of remote-proctored (or "at-home") assessments. The lack of standardized setting, device, or in-person proctor during at-home testing makes it markedly distinct from testing at a test center. Comparability studies of at-home and test center scores are important in understanding whether these distinctions impact test scores. This study found no significant differences in at-home versus test center test scores on a large-scale admissions test using either a randomized controlled trial or an observational study after adjusting for differences in sample composition along baseline characteristics. [ABSTRACT FROM AUTHOR]

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