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Freeze-thaw cycles in combination with long-term moisture exposure and traffic is a major threat to the performance of asphalt pavements. To enable characterisation and understanding of the damage ...

Crispness is the most appealing characteristic of dry food products. However, the term crispness has different subjective meaning among consumers. This study aims to quantitatively measure the crispness of potato crisp by performing compression test on a single specimen, and analyzing the compressive behavior, i.e., compressive strain energy. The crispness of the specimens were differentiated by changing the moisture exposure durations, which are 0, 1, 2, 3, 6 hours, in a room and ambient condition. The measured load and displacement data were transformed into stress and strain curves. The strain energy for every 1% strain increment was calculated and investigated to determine the crispness. The crispness difference among specimens of 0, 3, and 6 hours groups was significantly perceived at 8% of strain. It was revealed that the 3 and 6 hours of room air exposure could decrease the crispness by 17% and 45%, respectively. This suggests the compressive strain energy at a certain strain can be an indicator of crispness. This experimental study is expected to evolve food engineering by proposing a simple yet precise crispness measurement method for dry food.

Glass/Vinylester composite laminates are comprehensively characterised to assess its impact response behaviour under moisture exposure in marine structures. An instrumented drop weight impact machine is utilised to determine the impact responses of dry and immersed specimens in normal, salted and sea water. The specimens, which had three different thicknesses, were subjected to water exposure for a very long period of over 20 months before tested in a low-velocity impact experiment. Water uptake was measured primarily to study the degradation profiles of GRP laminates after being permeated by water. Matrix dissolution and interfacial damage observed on the laminates after prolonged moisture exposure while the absorption behaviour was found typically non-Fickian. The weight of the composite plates firstly increased because of water diffusion up to month 15 and then decreased due to matrix degradation. The specimens with 3, 6 and 9 mm thickness exhibited maximum water absorption corresponding to 2.6%, 0.7% and 0.5% weight gain, respectively. In general, the results indicated that water uptake and impact properties were affected by thickness and less by water type. Impact properties of prolonged immersed specimens reduced remarkably, and intense failure modes detected almost in all cases. The least sensitive to impact damage were wet specimens with 9 mm thickness as they indicated similar maximum load and absorbed energy for different impact energies.

Bonding strength between asphalt and aggregate is considered an important feature that governs the future performance of flexible pavements. This study investigated five factors that have the poten...

Slabs of polymer composite materials (PCMs) based on glass, carbon, and organic fillers and various binders were made according to one technological molding mode. The main methods for determination of the effects of thermal and moisture factors on the PCM properties were selected. The effect of thermal and moisture factors on the physical and mechanical properties of PCMs was studied. The studies have shown the positive effect of additional heat treatment of PCM on its properties. The microhardness of the matrix in the samples was investigated before and after heat treatment.

Herein, the influence of distilled water and alkaline solution on the scratch resistance properties of Napier fibre filled epoxy (NFFE) composites were investigated. The particulate Napier fibre form was mixed with epoxy resin to fabricate 5, 10, and 15 wt.% NFFE composites. Moisture exposure tests using distilled water and alkaline solutions were conducted to determine the critical time conditions of the composites. Scratch tests were performed to investigate the scratch resistance properties of the NFFE composites, such as critical normal load, coefficient of friction, penetration depth, fracture toughness and tearing extent. The results showed that with the increasing fibre content of the composites, the scratch resistance properties increased after exposure to distilled water and an alkaline solution. The 10 wt.% NFFE composites had the highest critical normal load and fracture toughness after exposure to distilled water and alkaline solution. Morphological observations showed that severe tearing occurred for all NFFE composites after exposure to the alkaline solution compared to distilled water.

Searching less toxic materials with both ideal bandgaps (1.0–1.5 eV for single-junction solar cells) and excellent stability remains a big challenge in perovskite optoelectronic materials field. Here, we report the optoelectronic properties and stability of the [H3NC6H4NH3]CuBr4 perovskite material. Intriguingly, the material features a bandgap of 1.43 eV which approaches that of GaAs (1.42 eV)—the state of the art semiconductor for single-junction solar cells. Furthermore, the [H3NC6H4NH3]CuBr4 film shows excellent stability, and can tolerate continuous moisture exposure for 1200 h in air (relative humidity: 40–50%) and ultraviolet light exposure for 1008 h in a glove box filled with nitrogen. Finally, we successfully realized a pinhole-free, smooth, and large-area (>20 cm2) [H3NC6H4NH3]CuBr4 film—the largest Cu-based perovskite film ever reported—via a hot-casting technique. Owing to its ideal bandgap and excellent stability, [H3NC6H4NH3]CuBr4 can be considered as a milestone in the development of low bandgap, highly stable, and lead-free perovskite materials for potential optoelectronic applications.

Clarification of how water affects the photovoltaic performance of perovskite solar cells is one of the major challenges to successfully develop a large-scale low-cost fabrication process. Many authors have reported beneficial effects of moisture during the fabrication of perovskite solar cells (PSCs), such as enhanced crystallinity, photoluminescence and photovoltage. However, the highest power conversion efficiency reported until this date was obtained under completely dry atmosphere conditions, avoiding the presence of water during perovskite formulation and preserving the damage caused by moisture exposure with encapsulation techniques. This apparent contradiction makes patent the necessity of an extensive clarification to establish the conditions in which water represents a beneficial or harmful factor in the development of high efficiency and stable perovskite devices. In this review, we summarized the effects of water, both as an additive into the perovskite formulation as an additive and as moisture exposure during fabrication. We discuss in depth the structural and chemical effects, analysing also the photovoltaic consequences during operation conditions. As a final input, we remark a useful method to perform high efficiency PSCs under different lab ambient conditions and highlight the latest advances in hydrophobic devices and encapsulation techniques.

A Pennisetum purpureum/glass-reinforced epoxy (PGRE) hybrid composites was comprehensively characterised to assess its impact response behaviour at room temperature (RT), under moisture exposure, and elevated temperatures. The untreated, 5 and 10% alkali-treated PGRE composites were fabricated using hybridised Pennisetum purpureum/woven E-glass fibres and epoxy resin. An instrumented IMATEK IM10 drop weight impact tester was utilised to characterise the impact responses of the prepared hybrid composites. The specimens were subjected to water exposure for 50, 100, 200, and 400 h and before arranged with a low-velocity impact test. In addition, the tests were repeated at 40, 60, and 80 °C to examine the effects of elevated temperatures. The results indicate that the untreated PGRE composite yielded the highest peak load impact response at all energy levels. The stiffness of the composites found to decrease substantially with increasing temperatures, which increases the absorbed energy and peak deflection causing extensive damage to the specimens.

This paper aims to investigate the spatially non-uniform frost damage process in RC beams during large numbers of freeze/thaw cycles (FTC). The material-based thermodynamic and poromechanical frost damage models have been up-scaled to the structural level considering the anisotropic stress-strain conditions and the condensed water movement in the crack system. The ice-induced pore pressures are also integrated in the smeared RC element in consideration of the path-dependent nonlinear constitutive laws. The frost damage accumulation processes (referred as the expansive strain) are simulated with different depths of heat and moisture exposure, as well as various arrangements of reinforcing bars. Based on the proposed empirical model which links the expansive strain with the reduction in ultrasonic velocity, the 3D frost damage profiles are compared with 2D ultrasonic velocity data, which show a satisfactory agreement. Finally, the effects of different steel and structural confinements on the frost damage profile are numerically investigated and discussed in detail.

This paper reports on the study of flexible epoxy resin which lowers modulus to minimize warpage while maintaining high filler content. Liquid Compression Molding (LCM) material is an encapsulation material applied at the wafer level. LCM requires high reliability and minimized warpage after curing. The flexible epoxy resin was studied to determine if it could be technically feasible to meet the requirements. Three epoxy resins with different structures, Conventional epoxy, and Flexible epoxy A and B, were examined. Both samples with Flexible epoxy A and B resulted in lower warpage than Conventional resin. Especially, Flexible epoxy B showed the minimal warpage with the lowest modulus. The sample with Epoxy B performs the best at 260 degree Celsius with the minimal warpage. A reliability test of LCM with Epoxy B was also conducted assuming the application for Fan-out packaging. Epoxy B showed no delamination or cracks under a thermal cycling test up to 1,000 cycles after MSL1 moisture exposure.

The development and multiaxial distribution of mechanical expansions caused by alkali-silica reaction were quantified for a large-scale reinforced concrete beam containing top and bottom mats of bidirectional reinforcement with no reinforcement through its depth. The effects of different conditioning environments and the influence of reinforcing bar size and layout on the expansion behavior of the beam were also considered. Expansions in the unreinforced direction exceeded those in the reinforced directions at all times. Expansions in the reinforced directions stopped prior to steel yielding and before concrete finished expanding in the unreinforced direction. Expansion behavior in biaxially reinforced beam regions was not influenced by triaxial restraint conditions at adjacent beam ends. Varying moisture exposure conditions along the length affected the time development of expansions but not the distribution of given volumetric expansions among primary directions.

Syntactic foams are commonly fabricated with sodalime–borosilicate glass hollow microsphere fillers, which are susceptible to degradation after long-term or high temperature moisture exposure. In comparison, borosilicate glass hollow particles offer higher degradation resistance to moisture, lower thermal expansion, and higher softening temperature. This work explores borosilicate glass hollow microspheres for use as fillers in syntactic foams and studies their thermophysical properties. The coefficient of thermal expansion over the temperature range 35–90℃ was observed to decrease from 62.4 μ/K for the matrix resin to a minimum of 24.3 μ/K for syntactic foams, representing higher thermophysical stability of syntactic foams. Theoretical models are used to conduct parametric studies and understand the correlation between material parameters and coefficient of thermal expansion of syntactic foams. The dynamic mechanical analysis results show that the storage modulus of syntactic foams increases with increasing glass hollow microsphere wall thickness and with decreasing glass hollow microsphere volume fraction in the glassy region at 40℃. The β-relaxation of the matrix resin found at 66.1 ± 2.0℃ was suppressed in the majority of syntactic foams, further improving the stability around typical application temperatures.

Compression after impact behaviour of Glass/Vinylester composite laminates, which have been subjected to water exposure for a long period of over 20 months, is studied. Furthermore, tests are carried out for three different specimen thicknesses aged in three different water types; potable, salted and sea water. The results of these tests are compared with those of non-impacted specimens to determine the change of the residual strength at different impact energies. The results show the load-displacement and load-strain curves of compression after impact tests. Moreover, the changes of residual compressive strength are determined with respect to the various imposed impact energy for different thicknesses. Failure modes and impact response of dry and wet specimens are discussed.

Environmental related durability issues have been of great concerns in the structures strengthened with the fiber reinforced polymers (FRPs). In marine environment, moisture is one of the dominant factors that adversely affect the material properties and the bond interfaces. Several short-term and long-term laboratory experimental investigations have been conducted to study such behaviors but, still, there are insufficient constitutive bond models which could incorporate moisture exposure conditions. This paper proposed a very simple approach in determining the nonlinear bond-slip models for the FRP-concrete interface considering the effect of moisture conditions. The proposed models are based on the strain results of the experimental investigation conducted by the authors using 6 different commercial FRP systems exposed to the moisture conditions for the maximum period of 18 months. The exposure effect in the moisture conditions seems to have great dependency on the FRP system. Based on the contrasting differences in the results under moisture conditions, separate bond-slip models have been proposed for the wet-layup FRP and prefabricated FRP systems. As for the verification of the proposed model under moisture conditions, predicted pull-out load was compared with the experimental pull-out load. The results showed good agreement for all the FRP systems under investigation.

Effect of environmental conditioning on scratch performance of polymethylmathacrylate (PMMA) is investigated. Three different grades of PMMA with varying levels of polarity were chosen and their scratch resistance compared in both dry and moist conditions. Linear increasing normal load scratch tests were performed according to ASTM D7027/ISO 19252 standards. Results indicate a drop in scratch resistance with initial exposure to moisture in all three systems. In the two highly polar PMMA systems, the scratch resistance recovers to that of the dry condition after long exposure to moisture. It is proposed that the moisture absorbed initially acts as a plasticizer causing weakening of the surface mechanical integrity. In the case of more polar systems this moisture absorption continues until saturation where water molecules cluster and impart a degree of lubrication and consequently improves scratch resistance.

When adhesively bonded joints are exposed to a moist environment, the tensile load capability of the joint is significantly decreased because moisture absorption weakens the mechanical properties of epoxy adhesive. In this paper, a nanoclay with excellent penetration resistance properties was used as a filler in epoxy adhesive in order to enhance adhesive strength in moist environments. The water absorption of the epoxy adhesive and the adhesive strength of the adhesively bonded joints were measured in water absorption experiments with respect to the weight fraction of the nanoclay and the moisture exposure time. These results showed that the tensile load capability of the nanoclay-filled adhesively bonded joint was greatly enhanced, even in a moist environment, because the nanoclay reduced water absorption into the epoxy adhesive as well as into the interface between the epoxy adhesive and the steel adherend and increased the strength of the epoxy adhesive itself.

Purpose – The authors aimed to develop environmentally stable NIR‐absorbing windows by blending a near‐infrared (NIR)‐absorbing dye and a photo‐crosslinkable polymer.Design/methodology/approach – To prepare an environmentally stable NIR‐absorbing window, a NIR‐absorbing dye was mixed with crosslinkable poly(vinyl cinnamate) (PVCn). The crosslinking of PVCn was carried out by photo‐dimerisation reaction of cinnamate with UV‐exposure at a wavelength of 254 nm for 4 min.Findings – The resistance of the photo‐crosslinked hybrid films against humidity, heat, and ultraviolet radiation damage was improved dramatically relative to the pristine NIR‐absorbing dye. These improvements result from the protection of NIR‐absorbing dye to moisture exposure in the presence of the polymer network.Originality/value – The simple and practical method resulted in a dramatic improvement in the environmental stability of NIR‐absorbing window.

Long-term moisture exposure has been shown to affect the mechanical performance of polymeric composite structures. This reduction in mechanical performance must be considered during product design in order to ensure long-term structure survival. In order to determine the long-term moisture effects on composite components, representative parts are commonly tested after having been exposed to an accelerated moisture conditioning environment. Accelerated moisture conditions are established in order to rapidly drive moisture into test specimens simulating worst-case long-term exposure scenarios. Currently, accepted methodologies for analyzing the time required to condition specimens are limited, allowing only simple geometry and an assumption that diffusivity rates are independent of the flow path or direction. Therefore, a more advanced finite element method is desired. In this study, a three-dimensional model is developed and implemented in commercial finite element code. The parametric study has been conducted for three-dimensional shapes, moisture diffusion pathways, and varying moisture and temperature conditions. Finite element results are validated with a one-dimensional analytical model and experimental results. A user-subroutine was implemented in commercial finite element code to calculate the moisture content. The ultimate goal for this research is to determine the exposure time for accelerated conditioning that produces the most accurate moisture distribution with the part and minimize over-conditioning of the laminate.

A crucial factor that affects all composite materials exposed to typical service conditions is environmental degradation . It has been shown that over time the combination of moisture and fluctuating temperatures degrades the structure of polymeric composites through chemical and morphological degradation mechanisms. Experimental investigations have not only demonstrated degradation of the polymeric matrix but also of the CNF–matrix interface due to surface morphology variation caused by weathering. This chapter aims to focus on the moisture effects on the structure and mechanical properties of CNF/polymer composites in an effort to offer insight into the mechanisms of degradation and failure under load after moisture exposure. However, information on this aspect of CNF/polymer composites is in the nascent stage and extensive future work is required.

Objective: To investigate the surface hardness of four conventional glass-ionomer cements: Ketac-Molar (KM), HiFi (HF), Vivaglass Fil (VF), Ketac-Fil (KF) and a newly developed glass polyphosphonate based cement, Diamond Carve (DC) at different maturation times in water and to investigate the effects of early water exposure on their surface hardness. Method: Disc specimens (10 mm diameter, 1 mm thick) were prepared and mould stored at 37°C. The effect of different maturation times (15, 30 and 60 min) and storage in water over 24 h after those maturation times on surface hardness was determined using a microindentor with a Vickers diamond indentor. The results of the surface hardness tests were analysed using Mann-Whitney non-parametric statistics (p≤0.05). The working (WT) and setting (ST) times of the cements were also measured using a modified Wilson oscillating rheometer. Results: All the materials became harder after 24 h immersion in water. HF, VF and DC showed initial sensitivity to a short maturation time, but only HF was adversely affected by early moisture exposure. KF and KM were least sensitive to short maturation time or early water exposure. DC had the shortest and HF the longest WT and ST. HF and VF had a high WT:ST ratio of 1:7 and 1:9, respectively. Conclusions: A short maturation time (of 15 min) and early exposure to water did not adversely affect the surface hardness of KF, KM, VF and DC. DC, based on poly(vinyl phosphonic acid), had the shortest WT and ST. Poly(acrylic acid) based HF and VF had a long ST in relation to their WT.

The effect of short-term environmental exposure on the response of in situ formed externally composite strengthened concrete is investigated. Measured response from static loading is described in terms of environmental degradation of composite and composite-concrete interface. Results indicate that degradation occurs primarily at the level of the resin in contact with the concrete, and that due care should be taken of changes in composite stiffness due to moisture exposure and consequent resin plasticization, as well as due to stiffness increases under cold conditions.

Moisture can play a critical role in the long-term failure of low-voltage oil-impregnated- paper insulated cables. The processes leading to incipient discharges and, over longer periods, to cable failure are considered. Measurements of commercially manufactured cable insulation conductivity are reported with cycling of temperature and ambient moisture levels. Moisture ingress into cable insulation is also directly measured using Karl-Fischer (KF) titration. Rapid increase in cable core temperature is shown to dramatically increase conductivity for a short period. Cycling of moisture exposure is shown to gradually increase insulation conductivity in both wet and dry states.

Effects of moisture exposure before cure of Scotchply 1009 composite material have been studied by three thermal analysis methods. These studies revealed the need for state-of-the-art analytical tools as well as increased attention to detail in packaging (by supplier) and improved handling (by user to reduce moisture exposure). It is shown that water definitely has a detrimental effect on the cure of Scotchply 1009 prepreg containing a boron trifluoride monoethylamine curing agent. Exposure to moisture greater than 70% RH (relative humidity) can be detrimental and lower the T/sub g/ of Scotchply 1009. Cure temperature high enough to ensure sufficiently high T/sub g/ in 1009 material which has been exposed to moisture can result in degradation of the thermosetting resin. In the manufacture of stator coils, this could cause degradation of electrical properties. >

Highly ordered mesoporous titania films were synthesized within a short time period by controlling the pH of sols and moisture exposure of as-prepared films.

The irreversible effects of moisture exposure on anhydride-crosslinked epoxy resin films are investigated by means of Fourier-transform infrared spectra. Hydrolytic attack of water at the ester linkages is accelerated in alkaline media and is a mechanically activated process. Matrix hydrolysis is also enhanced in the presence of inorganic fillers.

Auger electron spectroscopy and depth profiling have been used to obtain information on the composition of oxide films formed on high purity Al-5.5Zn-2.5Mg alloys as a function of heat treatment, grain size, storage environment, and temperature. These studies show that in the as heat treated condition the oxide film is predominantly MgO. The Mg/O peak to peak height ratio of this oxide is sensitive to the heat treatment temperature and exhibits a maximum at 475 C. During subsequent storage, especially in a moist environment, this film undergoes substantial changes in composition. The Mg/Al ratio of the oxide decreases due to formation of an Al rich oxide on top of the as heat treated oxide. A model is proposed to account for the changes in the oxide film composition during growth of the Al rich oxide, and possible implications to pre-exposure embrittlement and stress corrosion cracking (SCC) are discussed.

Moisture problems have perennially plagued the use of the electrical and electronic products. Carbon composition resistors represent a widely used component which must withstand the effects of moisture. Continual improvements in construction and materials have made this possible. To illustrate and magnify the changes that occur in commercial composition resistors with moisture exposure, molded resistors were prepared without insulating jackets or impregnant. Moisture changes are demonstrated to be largely reversible by drying and to be cumulative on extended or repeated moisture exposure. A good correlation was obtained between changes in length and resistance during moisture exposure. An impregnating wax is shown to reduce greatly the moisture susceptibility of the model resistors. Some comparative results obtained with different types of resin binder are also shown, indicating the significant contribution of this phase.

A comparative investigation of polyimide/Cu interface degradation has been carried out for ultrathin photosensitive, non-photosensitive, and preimidized polyimide precursor films cured while in contact with a Cu substrate. The role of curing byproducts and environmental conditions on interface degradation has been elucidated by means of X-ray photoelectron spectroscopy. Immediately after curing, we observed some oxidation of the Cu in contact with non-photosensitive and photosensitive polyimide overlayers. On the other hand, only negligible oxidation was observed for the preimidized polyimide/Cu interface. Experiments in which samples were stored in vacuum, air and a humidity chamber show a dependence of the oxidation kinetics on air/moisture exposure. Preimidized and photosensitive polyimide/Cu interfaces, stored in air, became more extensively oxidized with time relative to identical samples stored in vacuum. Moreover, all three polyimide/Cu interfaces exhibited significantly more oxidation after 3 days in a humidity chamber than after 19 days of storage in air. Taken together, these data clearly demonstrate that absorbed water and its interaction with curing byproducts are key factors in the extent of Cu oxidation at the interface.

A sample of titanium metal powder QC 1779 was subjected to five different treatments of dyring and moisture exposure to estimate the effectiveness of normal drying and handling procedures used in the pyrotechnics processing. The treatments were drying in air, drying in two different vacuum furnaces, exposure to normal humidity, and exposure to 100 percent humidity. Statistical evaluation of the NMR results indicates that there is a significant difference between the moisture content of each treatment. Although the combined effects of temperature, pressure, humidity, and treatment time were not studied in a designed manner to determine their significance on the effectiveness of the drying techniques and moisture uptake by sample QC 1779, the experimental evidence does indicate that all four variables do affect the results of the treatments. 2 figures, 6 tables.