Unaged Samples Research Articles

Hygrothermal aging behavior and mechanism of multi-filler reinforced epoxy composites for steel structure coatings

The long-term hygrothermal resistance of epoxy-based composites plays a key role as an anti-corrosion and anti-wear coating for steel structures when exposed to complex service environments. The hygrothermal aging will cause an irreversible damage to the service performances of composites. In the present paper, the multi-fillers reinforced epoxy composites (MFREC) had been successfully prepared and have been given higher expectations for steel coatings. Its hygrothermal aging behavior was experimentally investigated through the immersion in distilled water (DW) and saline water (SW) at 20, 40, and 60 °C as long as 120 days. The moisture uptake, thermal properties, mechanical properties and microstructure analysis were tested to evaluate the long-term hygrothermal evolution. The research results showed that the quasi-equilibrium moisture uptake content (3.72%) of MFREC in SW was lower than that (4.14%) in DW owing to the preferential permeation and occupation effects of small ions (Na+, Cl−). Hygrothermal exposure led to a maximum degradation of tensile strength, elongation at break and glass transition temperature of MFREC, up to 38.2%, 46.6% and 20.8% in DW, and 34.5%, 40.8% and 18.4% in SW, respectively. This was because the epoxy matrix had generated relaxation and reinforced-fillers/epoxy interfaces had been destroyed, which can be verified by hydrogen bond increasing (maximum 75.2%) from infrared test, fiber pulling out from epoxy matrix (morphology analysis), elastic modulus decreasing (maximum 37.8%) from micro-hardness measurement and pore volume increasing (maximum 53.9%) from N2 adsorption test compared to unaged samples. Based on the Arrhenius theory, the long-term life prediction of MFREC tensile strength under three typical bridge service environments was conducted to evaluate the service time as coatings. It can be found that the stable strength retentions were 63.19% and 66.03% in the simulated pure water and marine environments, respectively. Furthermore, an additional strength degradation percentage up to 11.5% can be found for MFREC exposed to steel bridge coatings in southern as long as 3 years compared to the northern environment.

Influence of modification of aged spruce wood by in situ polymerization with ethyl methacrylate and methyl acrylate and paraloid B72 on color and water absorption

Influence of modification of aged spruce wood by in situ polymerization with ethyl methacrylate and methyl acrylate and paraloid B72 on color and water absorption. Wood is hydrophilic in nature, which creates problems such as dimensional instability and susceptibility to biological degradation. By using chemical modification, wood can be refined into new products with improved properties. Such a combination of wood and polymer is called a wood-polymer composite (WPC). The presented work compares the modification of aged wood by two methods. In situ polymerization with ethyl methacrylate and methyl acrylate with modification with Paraloid B72 solution. The determinants of the modifications carried out are percentage weight gain (WPG), color change and water absorption. Unmodified wood aged and unaged were the control samples. Also unaged and modified wood samples were prepared to compare results. The greatest change in color intensity and total color difference after the aging process was recorded for samples modified with Paraloid B72, and after UV light treatment - modified by the in situ polymerization. The in situ-modified samples had the lowest water absorption among aged samples, and Paraloid B72-modified samples had the lowest water absorption among unaged samples. The highest WPG was obtained from the aged samples modified by the in situ polymerization.

Effect of solution concentration on ethylene propylene diene monomer (EPDM) nonmetallic components used in caustic liquid waste transfer lines

The hose-in-hose transfer lines (HIHTL) used to transfer waste at the United States Department of Energy’s Hanford Site Tank Farm are fabricated from an ethylene propylene diene monomer (EPDM) synthetic rubber. During waste transport, these hoses are exposed to several stressors including caustic solutions at high temperatures and high pressures, as well as β and γ radiation. The aging behavior of HIHTL and dog-bone shaped EPDM specimens were evaluated by exposure to solutions at 77 °C containing 0.00, 6.25, 12.50, and 25.00 % (v/v) sodium hydroxide (NaOH) for 12-months. After the exposure, the material properties of the specimens were measured and compared to the unaged samples. The material properties evaluated included the tensile strength of the EPDM dog-bone samples and the burst pressure of the HIHTL. Both the tensile strength of the EPDM dog-bone samples and the burst pressure of the HIHTL specimens exposed to the 6.25 % NaOH solution exhibited the most significant deterioration and those exposed to 25.00 % NaOH solution had the least deterioration. Examination of the HIHTL and the EPDM dog-bone specimens with scanning electron microscopy showed that the deterioration for the specimens exposed to 6.25 % NaOH solution were the most severe and the samples exposed to 25.00 % NaOH solution had the least deterioration.

Определение летучих органических примесей в виски методом газовой хромато-масс-спектрометрии

Alcoholic beverages are complex multicomponent objects. Their quality and safety control is a serious analytical task that requires new, more accurate instrumental methods, e.g., chromatography-mass spectrometry. 
 The research involved domestic and foreign whiskey, other alcoholic beverages, and 40% water-alcohol model solutions. The analytical studies were carried out on a Maestro 7820A gas chromatograph GC with an Agilent Technologies 5975 Series MCD mass selective detector, a G4513A autosampler, and a high polarity FFAP capillary column.
 The research revealed the optimal parameters of chromatographic separation and mass spectrometric detection. The relative measurement error remained below 25% in the range of 1.0–10 mg/dm3 and 18% in the range of 10–500 mg/dm3. These modes were used to study the composition of the volatile organic impurities. The largest proportion of the total volatile impurities was 34.84–58.08% isoamylol, 17.31–26.76% acetic acid, and 12.50–21.28% isobutanol. Other chemical compounds were not so abundant: 0.34–0.86% isoamyl acetate, 0.13–0.39% 1-butanol, 0.03–0.06% 1-pentanol, 0.40–11.20% ethyl lactate, 0.16–2.74% ethyl caprylate, 1.40–6.44% furfural, 0.18–14.60% ethyl caprate, 0.74–2.97% ethyl laurate, and 1.75–2.39% 2-phenylethanol. The maximal total content of volatile organic impurities was 2040.30 mg/dm3: it was registered in apple samogon. The minimal total content of volatile organic impurities was 392.16 mg/dm3 in the unaged rum distillate sample.
 The new method proved highly accurate in determining the qualitative and quantitative composition of twelve volatile consumable components in whiskey. The procedure took 17 min; it can be applied to mass concentrations of volatile impurities in such alcoholic beverages as grape-brandy, rum, tequila, brandy, samogon, rum, and various distillates.

Effects of aging treatment on microstructure and mechanical properties of non-equiatomic high entropy alloy

In this study, the cryogenically-processed FeCoNi1.5CuB0.5Y0.2 HEAs (high-entropy alloys) were subjected to aging treatment, such as different aging temperatures T (unaged sample, 700 °C, 750 °C, 800 °C), aging times t (unaged sample, 10 h, 12 h, 14 h) and the aging cycles N (unaged sample, one time, two times, three times). Under this condition, the changing laws of microstructure and mechanical properties of HEAs were explored. According to the experiment, with the increase of the aging temperature, the prolongation of the aging time or the growth of the number of aging cycles, the overall mechanical properties of the material have been significantly improved. In particular, when the aging conditions were T = 750 °C, t = 12 h, and N = 2 times, the grain size of the optimized sample was reduced, and a large number of finely dispersed precipitates appeared, which can produce excellent strong-plastic synergy. Further analysis revealed that the complex interacting multi-component in the HEA constitute the heterogeneity level of the microstructure and also lead to effective multi-component strengthening. Especially in the samples after optimized aging parameters (DCAT 7), the activated back stress at boundaries of grains and the synergistic effect of nanoparticles and twins contribute to high strain hardening. In terms of micromechanical characteristics, the modulus of elasticity and nanohardness of each phase were obviously enhanced. In terms of macroscopic mechanical properties, Vickers hardness, compressive strength and maximum compression ratio also reached their maximum values, which were 53.4%, 19.6% and 43.5% higher than those of the single cryogenic sample, separately. Obviously, the overall strength-ductility has been improved simultaneously.

Effect of artificial aging on 3-point bending behavior of glass fiber/epoxy composites

This study looked into how artificial aging affected the mechanical behavior of composites made of glass fiber reinforced polymer (GFRP). In this context, GFRP composites were produced by vacuum infusion method and artificially aged in the aging cabinet. Three different composite specimen types were tested. These are unaged samples aged 750 h and aged 1500 h. Three-point bending tests were performed to determine the mechanical properties. The absorbed energies of the samples were determined and the maximum bending stresses were calculated. The maximum contact force and sample displacements were also determined. In addition, the damage areas of the samples were examined optically and the changes that occurred with the aging time were determined. Finally, SEM images were taken to observe the changes in the internal structure of the aging and non-aging samples. According to results, as the sample aged, a decrease was observed in the energy values absorbed by the composite samples. In addition, as the aging time increased, it was determined that there was a spread in the damage area and more visible fiber breaks occurred. The increase in the aging time caused a decrease in the stiffness of the composite specimen, worsened its mechanical properties, and increased matrix damage.

Wear Analysis of Tibial Inserts Made of Highly Cross-Linked Polyethylene Supplemented with Dodecyl Gallate before and after Accelerated Aging.

The wear of the tibial insert is one of the primary factors leading to the failure of total knee arthroplasty. As materials age, their wear performance often degrades. Supplementing highly cross-linked polyethylene (HXLPE) with dodecyl gallate (DG) can improve the oxidation stability of tibial inserts for use in total knee arthroplasty (TKA). This study aimed to evaluate the wear resistance of HXLPE supplemented with DG (HXLPE-DG) tibial inserts before and after accelerated aging. HXLPE-DG tibial inserts were subjected to wear testing of up to 5 million loading cycles according to ISO 14243, and the resulting wear particles were analyzed according to ISO 17853. The wear rate, number, size, and shape of the wear particles were analyzed. The average wear rate of the unaged samples was 4.39 ± 0.75 mg/million cycles and was 3.22 ± 1.49 mg/million cycles for the aged samples. The unaged tibial inserts generated about 2.80 × 107 particles/mL following the wear test, but this was considerably lower for the aged samples at about 1.35 × 107 particles/mL. The average equivalent circle diameter (ECD) of the wear particles from the unaged samples was 0.13 μm (max: 0.80 μm; min: 0.04 μm), and it was 0.14 μm (max: 0.66 μm; min: 0.06 μm) from the aged samples. Moreover, 22.1% of the wear particles from the unaged samples had an aspect ratio (AR) of >4 (slender shape), while this was 15.4% for the aged samples. HXLPE-DG improves the wear performance of the material over time. HXLPE-DG is a novel material that has been demonstrated to have antiaging properties and high wear resistance, making it a promising candidate for use in TKA. Nevertheless, the results are preliminary and will be clarified in further studies.

Excellent tensile properties and deformation mechanisms in a FeCoNi-based medium entropy alloy with dual-heterogeneous structures

A dual-heterogeneous structure with both heterogeneous grain structure and coherent L12 nano-precipitate was obtained in a (FeCoNi)86Al7Ti7 medium-entropy alloy (MEA) after cold rolling, critical annealing, and aging treatments. The volume fraction of the L12 phase is found to increase from 0% to 34.5% after aging treatment, resulting in severer heterogeneity. The unaged samples of (FeCoNi)86Al7Ti7 MEA are found to have a much better synergy of strength and ductility as compared to the FeCoNi MEA. Moreover, the tensile properties for the aged samples of (FeCoNi)86Al7Ti7 MEA with dual-heterogeneous structures are even better than those for the corresponding unaged samples. The hetero-deformation-induced hardening plays a more important role in the aged samples than in the unaged samples, producing a higher density of geometrically necessary dislocations. High density dislocations are discovered in grain interiors for the aged samples and the deformation is dominated by the planar slip in the unaged samples. Meanwhile, a high density of dislocations are observed inside L12 nano-precipitates; thus, L12 nano-precipitates can be sheared by dislocations, indicating that L12 nano-precipitates are strong but deformable. The strong interactions between dislocations and L12 nano-precipitates should provide additional strain hardening for better tensile properties in the aged samples.

Evaluating the substitution potential of SBS with crumb rubber-polypropylene blends as asphalt binder and mixture modifiers

The study aimed to assess the suitability of substituting styrene–butadienestyrene with waste crumb rubber-polypropylene blends as modifiers to enhance the performance characteristics of asphalt binders and mixtures. Six crumb rubber-polypropylene blends including three styrene–butadienestyrene percentages were used to modify a base binder and then the modified binders were used to fabricate asphalt concrete mixtures. To obtain the physical and compatibility behavior of the unmodified and modified binders, various conventional binder tests such as softening point, penetration, and storage stability were employed. Dynamic shear rheometer, multiple stress creep recovery, and linear amplitude straintests were performed on unaged and long-term aged samples to achieve a broad understating of rheological characteristics at high and intermediate temperatures. In order to assess the influence of the modifiers on asphalt mixtures, various test methods were implemented including indirect tensile strength, resilient modulus, and four-point beam fatigue and dynamic creep tests. The findings of the physical tests represented a decline in penetration and a rise in softening point by the crumb rubber-polypropylene and styrene–butadienestyrene modifications compared with the base one. Results of the storage stability test proved that only 3% styrene–butadienestyrene modified was a storage-stable blend at high construction temperatures and the instability increased by incorporating more polymer content. According to the rotational viscosity test, all of the modifications increased the viscosity, reducing the workability of the modified mixture. Based on the rheological tests, the addition of the modifiers resulted in a reduction in phase angles, and an increase in complex modulus at high temperatures, thereby decreasing binder sensitivity to permanent deformation. With increasing the percentage of the polymer, more improvement would be obtained regarding rutting resistance. At intermediate temperatures, however, the complex modulus of modified binders decreased while no notable changes were observed for phase angle compared to the base binder. Considering the mechanical test results, the crumb rubber-polypropylene and styrene–butadienestyrene modified mixtures resulted in an enhancement in indirect tensile strength, resilient modulus, four-point beam fatigue, and dynamic creep tests results which would cause better resistance against rutting, fatigue damage, and moisture susceptibility compared with the base one. Besides, a radial bias function neural network model was designed to predict tensile strength ratio, and fracture energy ratio. The results showed the high performance of this method in the estimation of these values.

Deep learning for chemometric analysis of plastic spectral data from infrared and Raman databases

Increasing plastic recycling rates is key to addressing plastic pollution. New technologies such as chemometric analysis of spectral data have shown great promises in improving the plastic sorting efficiency to boost recycling rates. In this work, a novel deep learning architecture, PolymerSpectraDecisionNet (PSDN) was developed, consisting of convolutional neural networks, residual networks and inception networks in a decision tree structure. To better represent the conditions in the plastic recycling industry, the models were built to identify the most widely recycled polymers – polyethylene, polypropylene and polyethylene terephthalate from open-sourced infrared and Raman spectral dataset containing over 20 different polymers. PSDN performed better than end-to-end neural networks, obtaining an accuracy of 0.949 and 0.967 with the Raman and infrared datasets respectively. The use of deep learning can also distinguish between weathered and unaged polymer samples, with accuracies of 0.954 for high density polyethylene and 0.906 for polyethylene terephthalate.

Unusual phase transformation and novel hardening mechanisms upon impact loading in a medium entropy alloy with dual heterogeneous structure

Dynamic shear properties and corresponding deformation mechanisms of a CrCoNi-based medium entropy alloy (MEA) with both coherent nanoprecipitate and heterogeneous grain structure were investigated utilizing hat-shaped specimens in Hopkinson-bar and microstructure characterization. The present MEA with dual heterogeneous structure is found to have extraordinary dynamic shear properties, as compared to the other advanced metals and alloys, including the CrCoNi MEA with similar heterogeneous grain structure while with single FCC phase. A formula for considering effects of strain hardening, strain rate and thermal softening was utilized to calculate the critical shear strain for onset of adiabatic shear band for the present MEA, and the experimental results were found to be well predicted by the theoretical estimations. The formations of microscopic shear bands with low-angle grain boundary type, nano-grains, deformation twins, stacking fault network, and Lomer-Cottrell locks were found to be responsible for the multiple strain hardening mechanisms during dynamic shear deformation for both unaged and aged samples. An unusual phase transformation (γ→σ) was observed for only aged samples under dynamic shear loading, which was not found under quasi-static conditions before, should have significant contribution on strain hardening due to the precipitation by-passing hardening by the hard σ nano-particles.

Enhancing the asphalt binder's performance against oxidative ageing and solar radiations by incorporating rubber from waste tyres

• Comparisons were made between PAV and UV ageing of neat and rubber modified bitumen. • 1× PAV ageing cycle is compared with 1-year of Melbourne’s UV ageing. • Compared to neat bitumen, crumb rubber reduced the PAV ageing by 2.35 times. • Compared to neat bitumen, crumb rubber reduced the UV ageing by 1.30 times. This study investigates the ageing of neat and crumb rubber modified bitumen (CRMB) under various conditions. Bitumen was modified with a high content of crumb rubber (CR) (22.5% by weight of base bitumen) and subjected to the equivalent amount of UV radiation occurring in one year in Melbourne, Australia. Long-term ageing via pressure ageing vessel was also used to age CRMB. Fourier transform infrared spectroscopy (FTIR) was used to capture the mechanism and evaluate the ageing effect that UV radiation and PAV ageing had on both types of binders. It was found that PAV ageing, due to its high temperature and pressure, mainly involves the evaporation of volatiles, oxidation of bitumen, and the conversion of aromatics to asphaltenes, while UV radiations, on the other hand, destroy the molecular structure of bitumen in addition to providing oxidation. The effect of ageing on rheological performance parameters such as crossover modulus, J nr , and %R was also found in line with the findings from the FTIR spectroscopy. The ageing index developed from the crossover modulus showed that applying a 1-year equivalent of UV radiations in Melbourne (Australia) provides 1.51 times increase in ageing to the neat bitumen while ageing is up to 2.64 times after 20-hour PAV. When the same neat bitumen was modified with CR, the ageing resistance against both PAV and UV radiations was enhanced by limiting the level of ageing to 1.16 and 1.12 times, respectively. Kruskal-Wallis test showed that there is no significant difference between the unaged and aged samples of CRMB in terms of I com . That showed 20-h PAV ageing and 1-year UV ageing did not significantly affect the CRMB, which is evidence of the ageing resistance of CRMBs.

Achieving better synergy of strength and ductility by adjusting size and volume fraction of coherent κ’–carbides in a lightweight steel

Heterogeneous grain structures with dual-nanoprecipitates have been designed and fabricated in a lightweight steel. The size and the volume fraction of coherent κ’–carbides are increased by aging treatment, while the volume fraction of B2 precipitates and the heterogeneous grain structure are nearly unchanged after aging treatment. The aged samples are found to have a better synergy of strength and ductility, as compared to the unaged samples. The better tensile properties in the aged samples can be owing to the higher hetero-deformation-induced hardening and the higher density of induced geometrically necessary dislocations during tensile deformation. Two distinct precipitation hardening mechanisms are revealed for the dual-nanoprecipitates, i.e., bypassing mechanism for B2 precipitates and shearing mechanism for coherent κ’–carbides. Numerous dislocations can be observed both around and inside coherent κ’–carbides. High density of stacking faults and nanotwins can also be found in the grain interiors of the aged samples, resulting in strong strain hardening by interaction between them and dislocations. The better tensile properties in the aged samples can also be attributed to the stronger shearing precipitation hardening effect by larger size and higher volume fraction of coherent κ’–carbides.

Test method for abrasion behavior of tire tread compounds using the wear particles

The abrasion behavior of model tire tread compounds was characterized by the shapes and size distributions of their wear particles. Carbon black-filled NR/BR vulcanizates with varying compositions (NR/BR = 100/0, 80/20, and 60/40) were used. These were thermally aged at 80 °C for 30 days. The wear particles produced from the aged specimen had rougher shapes than those produced from the unaged specimen. The size distributions of wear particles for the aged specimen were smaller than those for the unaged specimen. The wear particles produced from the NR = 100 sample had a larger size distribution than those produced from the NR/BR blend samples. The size distributions of wear particles smaller than 500 μm were found to be closely related to the crosslink density irrespective of the rubber composition and thermal aging. The aged samples exhibited narrower abrasion patterns than their unaged samples. Furthermore, the spacing and depth decreased as the BR content increased. The abrasion patterns were closely related to the size distributions of wear particles. The abrasion rates and the number of wear particles significantly increased after the thermal aging. The abrasion behavior was mainly affected by the crosslink density, rubber composition, presence of antidegradants, and tensile strength. By analyzing the shapes and size distributions of the wear particles and the crosslink densities, the abrasion behavior could be further elucidated.

Influence of heat aging on tensile test in rubber-epoxy composites

Composite materials using natural rubber as the main matrix are popular these days because of the wide applications of rubber materials in modern industries. Rubber materials also have damping properties, energy absorption, and exposure to continuous loads and different environmental conditions. In this research, the effect of temperatures on the rubber-epoxy composite with different ratios (0%, 10%, 20%, 30%, 40%, and 50%) of carbon has been studied. Where comparison was made between heat-aged and un-aged samples using the tensile test. To know the effect of high temperatures on the rubber-epoxy composite, it was done in a heated oven at a temperature of 70. The results obtained from the tensile test observed a decrease in tensile strength and elongation when exposed to thermal aging.

Numerical and predictive analysis of the low-velocity impact response of UD composite plate under a controlled environment

The present paper proposes an investigation and analysis study of a low velocity impact on a unidirectional S2-Glass/Polyester composite plate subject to a controlled environment. A set of simulations of low velocity impact on unaged and aged samples in a bending configuration were carried out. A mass diffusion is studied in order to use its outputs as a predefined field which will be combined with the velocity of the impact loads. The diffusive and mechanical responses, such as moisture concentration, the effect of temperature, energy dissipation and impact force are highlighted and analysed. To ensure the validity of the finite element model, a comparison study has been carried out and compared against experimental investigation founded in the literature. The adopted finite element model performance for the low velocity impacted composite plate under hygrothermal conditions strongly matches with the experimental findings and represents a clear improvement of the model. The impact of the moisture concentration on recorded contact force and energy is highlighted, particularly the delayed contact time and the reduction of the contact forces and the recorded energies intensity. Accordingly, two main factors have affected the contact force responses. These two factors are the drop height and the humidity concentration. An analysis of the maximum contact forces using the design of experiments (DOE) is performed. The effect of both factors namely, the drop height and the humidity concentration, on the response is highlighted as well as the effect of their interaction. The predictive model is highly effective and eases the reproducibility of other mechanical responses.

Effect of Styrene Butadiene Styrene on Properties of Open-Graded Asphalt Concrete Mixtures

Open graded asphalt mixture is becoming more widespread where it is applied for various purposes, e.g. drainage of rainwater effectivity, traffic safety (high skid resistance), and controlling pollution noise. However, it has many other disadvantages, of which low stability, high stripping, and moisture sensitivity. The research aims to study the effect of styrene butadiene styrene SBS addition on the volumetric and mechanical properties of open graded mixture. In this research one type of aggregate with gradation (12.5 mm NMAS), asphalt of penetration grade (40/50), and cement as filler were used. Optimum asphalt content was selected based on the criteria of air voids content, asphalt drain down, permeability, and abrasion resistance (for aged and un-aged) samples. Other properties of open-graded mixtures, such as indirect tensile strength (ITS), moisture susceptibility, Marshall stability and flow were evaluated. The results show that addition of polymer (SBS) leads to an enhancement in the properties of the modified mixtures. There is an improvement in Marshall parameters. Also, a slight decreasing is noticed for permeability and air voids. For Cantabro abrasion loss (aging and un-aging condition), the abrasion resistance is increased, the drain down of asphalt is decreased from original mixture by addition of SBS. Finally, the moisture sensitivity is improved indicating that modified mixes becomes more resistant to water damage.

Superior dynamic shear properties and deformation mechanisms in a high entropy alloy with dual heterogeneous structures

Both heterogeneous grain structure and dual nanoprecipitates were designed in a Al0.5 Cr0.9FeNi2.5V0.2 high entropy alloy (HEA), and the dynamic shear responses were investigated by hat-shaped specimens in split Hopkinson pressure bar tests. The present HEA with heterogeneous structure displays an unprecedented synergy of dynamic shear strength and ductility, as compared to the literature data for other metals and alloys. The excellent dynamic shear properties in the unaged samples could be due to the dynamical grain refinement, the dislocations hardening, and the precipitation hardening. The aged samples with a higher volume fraction of coherent L12 nanoprecipitates display even better dynamic shear properties, as compared to the unaged samples, which can be attributed to the triggered planar dislocation slip, the stored higher density of dislocations, the formation of dislocation substructure and the more pronounced precipitation hardening for postponing the occurrence of the adiabatic shear band (ASB). The high strain rate, high strain/stress magnitude, high adiabatic temperature rise, and fast-cooling process within ASB were observed to induce the dynamic recrystallization and the phase transformation from FCC phase to B2 phase, and this newly observed phase transformation phenomenon was not observed before under quasi-static deformation conditions.

Pre- and Post-Failure Experimental Bending Analysis of Glass Elements Coated by Aged Anti-Shatter Safety Films

The main goal of Anti-Shatter Films (ASFs) applications for structural glass is to create a barrier able to keep together fragments and minimize risk after any impulsive or static load that could lead glass to cracking. The influence of ASF properties on the flexural strength of coated glass elements is thus a relevant topic for safe design purposes, but still little investigated. To this aim, an experimental material investigation is presented in this paper, in order to achieve a good knowledge of common ASFs from a chemical point of view. Moreover, the deterioration of mechanical and adhesion characteristics for ASF samples subjected to different environmental conditions and accelerated ageing is also investigated, so as to simulate the effects of long-term exposure to high humidity (HU) or high temperature (HT). An experimental campaign carried out on 20 small scale ASF-coated glass specimens is finally presented, based on a three-point bending (3PB) test setup. The out-of-plane bending response of unaged or aged samples is performed by taking into account two different displacement-rate levels, to assess their performance and bending capacity under steady-static or impulsive loads. In both cases, the attention is given to the characterization of elastic and post-failure performances. Finally, support for the interpretation of experimental outcomes is derived from a simplified theoretical model of composite beam with partial connection, in order to estimate the shear stiffness of ASF adhesive components in the elastic stage.

Contributions of atmospheric plasma treatment on a hygrothermal aged carbon/epoxy 3D woven composite material

In this paper, the effects of hygrothermal ageing and atmospheric plasma surface treatment on a 3D carbon/epoxy-amine woven composite material are studied. The goal is to study the surface evolution of the materials in terms of chemical composition and morphology. Plasma treatment is applied on new and hygrothermally aged samples in order to analyse its contribution to the surface modifications and degradations. It appears that hygrothermal ageing has irreversible absorption behaviour causing hydrolysis, oxidation and particle losses, which modifies the surface chemistry and topology. On the other hand, the atmospheric plasma causes oxidation of the matrix. Indeed, when a repair is necessary, the damaged part could evolve due to moisture absorption related to ageing. As the fibres are exposed, the topology and surface chemistry are modified. Nevertheless, it allows to desorb the humidity adsorbed on the surface and reach an oxidation level similar to unaged treated samples.