Visualization of Thermal Effects in Polypropylene-based Composites under Cyclic Bending Tests

Studies on weight reduction in aviation and space vehicles have gained momentum recently. Thermoplastic matrix composite materials are important alternative materials, especially due to their high specific strength, formability and recyclability. In this study, it is aimed to investigate the mechanical behavior of fiber reinforced thermoplastic composites for different fiber and layer configurations. Thermoplastic composite materials used in the study were produced by lamination technique. In composite production; Glass fiber and carbon-aramid hybrid fabrics were used as fiber, and polyethylene granules were used as matrix. Thermoplastic sheets were obtained by keeping polyethylene granules and woven fibers in the hot press for a certain period of time. The damage behavior of the composite test specimens under tensile load was tested for the number of layers and fiber type. As the number of layers increased, stiffness, damage load and deformations increased in thermoplastic composites. Using hybrid fabric instead of glass as fiber material increased the maximum damage load by 100%.

An important element of swimming training is the improvement of muscle strength and the technique of swimming movements on dry land. The heat generated by the muscles involved in the effort contributes to a change in the temperature of the skin surface, which can be assessed by the IRT method. The aim of the study was to assess the symmetry and dynamics of changes in surface temperatures of selected areas of the body in swimmers after exercise on a swimming ergometer with the use of IRT. A total of 12 swimmers (aged 19 ± 1.3 years) completed a two-minute stress test (front crawl swimming movements) using a VASA Swim Ergometer, with a load of 5. Using an IRT camera (FLIR E60), postexercise changes in back and upper limbs surface temperature in relation to the resting values were observed. After exercise, the temperature value of all assessed areas decreased, apparently in the area of the back and the back of the arms, returning to the baseline values after 12 min of observation. There was no asymmetry in mean temperature values between the right and left upper limbs. IRT is a noninvasive and sensitive tool for the individual analysis of changes in body surface temperature in swimmers after training on dry land.

Borehole temperature profiles provide a record of ground surface temperature (GST) change at the decadal to centennial time scale. GST histories reconstructed from boreholes are particularly useful in climate reconstruction if changes in GST and surface air temperature (SAT) are effectively coupled at decadal and longer time periods and it can be shown that borehole temperatures respond faithfully to surface temperature changes. We test these assumptions using three boreholes in northwestern Utah that have been repeatedly logged for temperature over a time span of 29 years. We report 13 temperature‐depth logs at the Emigrant Pass Observatory borehole GC‐1, eight at borehole SI‐1 and five at borehole DM‐1, acquired between 1978 and 2007. Systematic subsurface temperature changes of up to 0.6°C are observed over this time span in the upper sections of the boreholes; below approximately 100 m any temperature transients are within observational noise. We difference the temperature logs to highlight subsurface transients and to remove any ambiguity resulting from steady state source of curvature. Synthetic temperature profiles computed from SAT data at nearby meteorological stations reproduce both the amplitude and pattern of the transient temperature observations, fitting the observations to within 0.03°C or better. This observational confirmation of the strong coupling between surface temperature change and borehole temperature transients lends further support to the use of borehole temperatures to complement SAT and multiproxy reconstructions of climate change.

Solder joints between a package and a printed wiring board (PWB) of a portable electronic device sustain thermal cycling as a result of power on-off, cyclic bending by key pad operation, and impact bending by dropping. Therefore, the authors conducted heat cycling, cyclic bending, and cyclic impact bending tests on the ball grid array solder joints between a chip scale package and a PWB. The evaluated solders were Sn-3 Ag-0.5 Cu and Sn-37 Pb. The tests showed that the life cycles of the Sn-3 Ag-0.5 Cu solder joints for the feat cycling and cyclic bending tests were approximately twice those of the Sn-37 Pb solder joints. On the other hand, in the case of cyclic impact bending test, the life cycle of the Sn-3 Ag-0.5 Cu joint under large strain was smaller than that of the Sn-37 Pb solder joint because of interfacial crack growth between the solder and the PWB. These fatigue lives of the joints were compared with crack initiation and failure lives of plain specimens by calculating local strain ranges in the joints by elastic plastic finite element analysis.

Mechanical durability of screen-printed flexible silver traces for wearable devices

Twenty‐seven thermal survey cruises made over 4 years, and 1 year of remotely sensed surface temperatures were used to examine areal, diurnal, seasonal and interannual changes in the temperature of the Dead Sea and in its heat storage.The satellite data, corrected for a cold bias attributed to the anomalous depth and turbidity of the Dead Sea's atmosphere, indicate a very small areal variation in sea‐surface temperature (SST), typically less than 0·3°C over two‐thirds of the sea surface. The maximum value measured, 4·5°C, was at night in mid‐winter. Below‐surface temperatures showed much larger areal variations caused by the shallower thermocline in the north of the sea. This variability was the reason for the large number of measurements required to assess accurately seasonal changes in heat storage.Diurnal variations in SST were at their maximum, 3°C, in May, and at their minimum, 0·3°C, in December. During the summer, diurnal differences were clearly evident at a depth of 5 m, with some evidence that a layer twice as deep could be affected.Seasonal variation in SST was not symmetrical. From mid‐March to early July, surface temperature increased uniformly at 0·10°C day−1, between mid‐September and mid‐November the cooling rate, 0·13°C day−1, was also constant. In January and February, and July and August, SST was almost constant, with day‐to‐day changes less than 0·01°C. The seasonal amplitude in SST was 11·5°C at the surface, 9·6°C at 25 m depth, halved at 35 m, and was reduced to one‐tenth, 1·4°C, at 50 and 75 m.No significant interannual changes in surface temperature were found since the mid‐winter rise of 3·4°C that occurred 30 years ago. During the last decade the maximum seasonal depth of the thermocline has progressively deepened to 30 m. and below this depth an increase in the temperature of the deeper waters is evident. Possible sources of this heating are discussed.Seasonal changes in the heat storage were in phase with those in the surface temperature, with maximum values of 9·1 MJ m−2 day−1 in June and –8·7 MJ m−2 day −1 in December. The heat budget (intra‐annual range) of the Dead Sea. 1.16 GJ m2, is one of the highest reported in the literature, although less than that expected from its depth and radiation balance. The sea's heat content increased by an average of 224 MJ m−2 year−1 during the 4 years of this study; the large year‐to‐year variation in this heating was negatively correlated with the fall in sea level.

Non-Amazonian South America has one of the highest rates of conversion of native ecosystems globally. Most of the studies investigating the climate impacts of these changes focus on the Amazon while the possible influences that these changes may have on climate of non-Amazonian regions have received less attention. The aim of this thesis was to evaluate the impacts of land use and land cover on the mean and extreme climate of non-Amazonian South America by conducting modelling experiments for pre-clearing (before year 1500) and present (year 2005) land covers. It develops new data sets of changes in land surface characteristics for this period and applies a high resolution regional climate model to simulate the potential impacts of changes in natural vegetation cover. The thesis begins by providing a theoretical framework of surface-atmosphere interactions. It then reviews the process of land use and land cover change and subsequent climatic consequences in non-Amazonian South America and identifies those ecosystems most affected and least studied. The review highlights that non-Amazonian regions have lost more than 3.4 million km2 of natural vegetation since European colonization. Despite the magnitude of ecosystem loss, non-Amazonian South America accounts for significantly fewer studies addressing land surface-atmospheric processes compared to the Amazon region, highlighting the knowledge gap in relation to the main topic of this thesis. Based on these results, the following chapters address this knowledge gap by focusing on the climatic impacts of land use and land cover change in four main ecosystems: the Atlantic Forest (Brazil, Argentina and Paraguay), Cerrado (Brazil), Dry Chaco (Argentina, Bolivia and Paraguay) and the Chilean Matorral (Chile). I then apply the variable resolution CSIRO Conformal Cubic Atmospheric Model (CCAM) global climate model at a 25 km spatial resolution over the South American continent to quantify the seasonal climate impacts of each of historic land cover change. The results of computed modelling experiments show significant changes in surface fluxes, temperature, precipitation and moisture in all ecosystems. For instance, simulated temperature changes were stronger in the Cerrado and the Chilean Matorral with an increase of between 0.7 and 1.4 °C. Changes in the hydrological cycle revealed high regional variability. Results also show that the loss of natural vegetation has significantly affected temperature extremes as a decrease in the number of warm days and an increase in the number of warm nights. Importantly, there is a strong dependence on both seasonality and the vegetation contrast inflicted by land use/cover change, with large roughness changes resulting in increasing wind speed and advection, while smaller roughness changes result in feedbacks more reliant on the distinction between sensible and latent heat fluxes. This explains the dry season response in both temperature extremes and the increase in aridity according to land use/cover change, whereby regions with increased wind speed reduce warm day temperature extremes, despite increasing mean temperature trend, and have a greater impact on atmospheric water demand than those regions that mainly increase sensible heat fluxes. These results can explain the observed trends in temperature extremes in non-Amazonian South America and highlights the need to embed land use/cover change as a forcing within future climate change scenarios. The main conclusions of the thesis are: a) non-Amazonian South America is one of the most impacted and least studied regions worldwide in terms of climatic impacts of land use and land cover change, b) modelled impacts of this process are expressed as significant changes in surface temperature and the hydrological cycle through changes in soil and atmospheric moisture, and have increased the aridity in all the examined ecosystems. The thesis highlights the importance of considering the influence of land use and land cover on the mean and extreme climate through changes in biophysical properties that significantly impact the surface-atmospheric coupling and therefore the hydrological cycle. This is critical consideration for national natural ecosystem management strategies as conserving and restoring natural vegetation cover may help mitigate the negative consequences of climate change and therefore have a direct influence on the welfare of the region’s 200 million inhabitants.

To meet the low warming targets proposed in the 2015 Paris Agreement, substantial reduction in carbon emissions is needed in the future. It is important to know how surface climates respond under low warming targets. The present study investigates the surface temperature changes under the low-forcing scenario of Representative Concentration Pathways (RCP2.6) and its updated version (Shared Socioeconomic Pathways, SSP1-2.6) by the Flexible Global Ocean-Atmosphere-Land System (FGOALS) models participating in phases 5 and 6 of the Coupled Model Intercomparison Project (CMIP5 and CMIP6, respectively). In both scenarios, radiative forcing (RF) first increases to a peak of 3 W m−2 around 2045 and then decreases to 2.6 W m−2 by 2100. Global mean surface air temperature rises in all FGOALS models when RF increases (RF increasing stage) and declines or holds nearly constant when RF decreases (RF decreasing stage). The surface temperature change is distinct in its sign and magnitude between the RF increasing and decreasing stages over the land, Arctic, North Atlantic subpolar region, and Southern Ocean. Besides, the regional surface temperature change pattern displays pronounced model-to-model spread during both the RF increasing and decreasing stages, mainly due to large intermodel differences in climatological surface temperature, ice-albedo feedback, natural variability, and Atlantic Meridional Overturning Circulation change. The pattern of tropical precipitation change is generally anchored by the spatial variations of relative surface temperature change (deviations from the tropical mean value) in the FGOALS models. Moreover, the projected changes in the updated FGOALS models are closer to the multi-model ensemble mean results than their predecessors, suggesting that there are noticeable improvements in the future projections of FGOALS models from CMIP5 to CMIP6.

Natural fiber-reinforced composites are becoming a growing trend because of their affordability, sustainability, abundant natural source, and minimal environmental effect. It has also shown to be an effective replacement of synthetic fiber, particularly in the transportation and construction sectors as ceiling, paneling, partition etc. In this study the jute fiber (Hessian Cloth) reinforced (10% to 50% fiber content by weight) Polypropylene (PP) and Polyethylene (PE) composite were made by compression molding technique to understand the effect of fiber loading on mechanical properties of two different thermoplastic composite materials. For jute fabric-reinforced thermoplastic composites, it was discovered that with 30 % fiber loading with PP and PE yielded the best results. It was found that the mechanical properties of the composites enhanced significantly with 30 % fiber content with PP and PE thermoplastic matrixes in contrast to 10% and 20% fiber content composites. However, increasing the fiber content over 30%, dramatically decrease the mechanical properties of the composite samples. The relationship between Tensile Strength (TS), Bending Strength (BS), Impact Strength (IS) and Tensile Modulus (TM), Bending Modulus (BM) was examined, along with water resistance properties for both composites. Additionally, the jute-reinforced polypropylene (PP) composite showed superior mechanical capabilities compared to the jute-polyethylene (PE) composite. This suggests that it could be a suitable replacement for the toy manufacturing, home or garden furniture, automotive and interior construction industries in the future.

Recently, as the development of thermoplastic resin with excellent property and forming process of thermoplastic resin composite material, research of thermoplastic resin becomes a hot issue in related areas. Comparing with common composite material, thermoplastic resin composite material has many advantages, such as, excellent impacting resistance and many processes. So, more and more researchers focus in thermoplastic resin composite material. In this article, applications of carbon fiber strengthen thermoplastic resin composite materials are comprehensive.

The system-in-package (SiP) is widely used in communication device that integrated multi components and packages into one system. However, the board level reliability performance becomes more important, especially cyclic bending test. In the work, both experimental and numerical model are performed to investigate the four point cyclic bending test with different load displacement. The bending test experiment was analyzed by Weibull method to calculate the solder fatigue life of SiP module. A three-dimension finite element method (FEM) and the Anand's visco-plasticity Model are used to simulate solder's creep behavior under cyclic bending test. It was constructed and experimentally benchmarked to qualitatively figure out solder joint failure location in whole package and crack position in solder interconnection. Besides, the constructive index, plastic work density (PWD) accumulated per cycle, is used to evaluate the risk of solder fatigue cracking failure and be correlated well from experimental characteristic cycles. This work provides design guideline for SiP module board level reliability under bending test. The factors that underfill dispensing effect and material type suggestion are also considered in this work.

Many industries, notably the automotive and aerospace industries, are now utilizing thermoplastic matrix composites (TPMCs) for their improved strength and stiffness properties compared to pure thermoplastic polymers, as well as their manufacturability compared to traditional thermoset matrix composites. The increase in the utilization of TPMCs ushers in the need for the development and characterization of joining methods for these materials. A widely used technique for joining thermoplastics is ultrasonic spot welding (USSW). During USSW, high frequency, low amplitude vibrations are applied through an ultrasonic horn resting on the polymer surface. The vibrations induce frictional heat, producing a solid state joint between polymer sheets. Advantages such as short weld cycle time, fewer moving components and reproducibility make this technique attractive for automation and industrial use. Prior work showed USSW as a feasible, repeatable joining method for a polycarbonate matrix filled with chopped glass fibers. The mechanical properties required for full characterization of the TPMC used in this work were not provided by the manufacturer. As such, the constitutive behavior of both as-received and USSW thermoplastic composite material (polypropylene matrix filled with 30 wt% chopped glass fibers) was characterized. The fiber orientation and distribution in TPMCs has a direct impact on constitutive behavior. To characterize these qualities, optical techniques such as scanning electron microscopy (SEM) and micro computed tomography (micro-CT) were employed. Digital image correlation (DIC) was used to acquire full field strain measurements from the composite material under different loading scenarios. Because the constitutive behavior of polymers is greatly dependent on temperature, temperature measurements during the USSW process and measurement of mechanical properties as a function of temperature will be conducted through infrared (IR) imaging and dynamic mechanical analysis (DMA), respectively. Following the calibration of the constitutive model for the polypropylene matrix TPMC, the mechanical and thermal properties will be used to develop a computational framework for the purpose of predicting the structural response of a composite joint under various loadings.

The variability of near surface temperature on global and regional spatial scales and interannual time scales from a 1000 year control integration of the Hadley Centre coupled model (HADCM2-CTL) are compared with the observational record of surface temperature. The model succeeds in reproducing the observed patterns of natural variability, with high variability over the northern continents and low variability over much of the tropics. The model global mean variability has similar strength to observed global mean variability on time scales less than 20 years. The warming seen in the historical record is outside the range of natural variability as simulated in HADCM2-CTL. The model has El-Nino/Southern Oscillation (ENSO)-like behaviour with a central Pacific, peak to peak, strength of approximately 3 K. Changes in near surface temperature in the central Pacific are strongly correlated with changes in near surface temperature over most of the tropics, large regions of the extra-tropics and changes in tropical ocean upper 250 m heat content. Tropospheric temperature changes and tropical surface pressure changes are also strongly correlated with changes in the central Pacific surface temperature. Oceanic regions show significant departures from an AR1 or first order Markov behaviour in the Northwest Atlantic, Northwest Pacific and Arctic oceans. The Northwest Atlantic region has large amounts of variability over periods greater than 50 years. This variability is associated with a jump in the strength of North Atlantic meridional stream function. The spectra of the Western European and Continental US land regions are not significantly different from an AR1 process. The flow through the Drake Passage has an interannual standard deviation of approximately 2.5 Sv with significant departures from an AR1 process at time scales greater than 40 years. Winter northern hemispheric 500 hPa geopotential height shows some evidence of multiple regimes but no year to year persistence of these regimes.

Understanding how biological markers of stress relate to stressor magnitude is much needed and can be used in welfare assessment. Changes in body surface temperature can be measured using infrared thermography (IRT) as a marker of a physiological response to acute stress. While an avian study has shown that changes in body surface temperature can reflect the intensity of acute stress, little is known about surface temperature responses to stressors of different magnitudes and its sex-specificity in mammals, and how they correlate with hormonal and behavioural responses. We used IRT to collect continuous surface temperature measurements of tail and eye of adult male and female rats (Rattus norvegicus), for 30 minutes after exposure to one of three stressors (small cage, encircling handling or rodent restraint cone) for one minute, and cross-validated the thermal response with plasma corticosterone (CORT) and behavioural assessment. To obtain individual baseline temperatures and thermal responses to stress, rats were imaged in a test arena (to which they were habituated) for 30 seconds before and 30 minutes after being exposed to the stressor. In response to the three stressors, tail temperature initially decreased and then recovered to, or overshot the baseline temperature. Tail temperature dynamics differed between stressors; being restrained in the small cage was associated with the smallest drop in temperature, in male rats, and the fastest thermal recovery, in both sexes. Increases in eye temperature only distinguished between stressors early in the response and only in females. The post stressor increase in eye temperature was greater in the right eye of males and the left eye of females. In both sexes encircling may have been associated with the fastest increase in CORT. These results were in line with observed behavioural changes, with greater movement in rats exposed to the small cage and higher immobility after encircling. The female tail and eye temperature, as well as the CORT concentrations did not return to pre-stressor levels in the observation period, in conjunction with the greater occurrence of escape-related behaviours in female rats. These results suggest that female rats are more vulnerable to acute restraint stress compared to male rats and emphasise the importance of using both sexes in future investigations of stressor magnitude. This study demonstrates that acute stress induced changes in mammalian surface temperature measured with IRT relate to the magnitude of restraint stress, indicate sex differences and correlate with hormonal and behavioural responses. Thus, IRT has the potential to become a non-invasive method of continuous welfare assessment in unrestrained mammals.

It is a known fact that aerospace industry requires very strict requirements in terms of weight, material properties, and product lifetime performance. Therefore, composite materials are key candidates to satisfy these stringent requirements. Thermoplastic composites have become more competitive in the fields of aerospace, defense, energy, electronics, and automotive industries compared to thermoset composites, due to their ease of formability, short production cycles, and recyclability. Considering the benefits of thermoplastic composite materials, more thermoplastic parts will be produced in near future in aerospace industry. This study highlights the most recent advancements in thermoplastic composite technology. The latest advances in thermoplastic composite technology are highlighted by reviewing material technologies and production methods. Conclusion of this study, it has been observed that the use of thermoplastics in the aerospace industry is increasing day by day, owing to the advantages they offer compared to traditional materials. Especially in critical and trending areas such as stamp forming, press consolidation, Automatic Fiber Placement (AFP), and welding methods, research and development activities are intensifying. Furthermore, this study provides insights into the direction of current investments in thermoplastic technology and discusses how these investments are likely to shape future applications within the aerospace industry.