Moulding Conditions Research Articles

Moisture Absorption Evolution of Gfrp Laminates Subjected To Different Environmental Conditions

Fibre composites are being used in various applications from aerospace, military, marine boats and submarine to renewable energy generation. Higher energy demands across the developed and growing world for the usage and replacement of conventional materials with polymer composite materials for engineering applications which is always questioned by the end user, unless the research oriented reliable supporting certification is made available. The reinforcement materials are highly hygroscopic, the matrix material provides protection to the reinforcement. When the parts made of composite materials are exposed to environment, water molecules travel along the reinforcement and cause damage to the interfacial bonding, further the performance of the composite laminate get effected. In this scenario, the investigation related to this aspect requires quantitative assessment which is carried out with accelerated simulation of the real time situation to provide a scope to chacterization of Glass fibre reinforced polymer composite (GFRP) laminates subjected to variable environmental conditions. This investigation was to study the effect on weight gain and mechanical property of GFRP laminate subjected to different environmental conditions. The test results reviled that remarkable reduction in tensile property and moisture absorption for samples in water absorbed more moisture than NaOH and salt water. Keywords: Glass fibre reinforced polymer composite (GFRP), Resin transfer moulding(RTM), Moisture absorption, tensile modulus and Environmental conditions.

Process capability study of rapid silicon moulding for plastic components

The purpose of the present study is to investigate process capability of rapid silicon moulding for plastic components. Starting from the identification of component, prototypes with two different type of plastic material were produced under different vacuum moulding conditions. Measurements on the coordinate measuring machine helped in calculating the dimensional tolerances of the plastic components produced. Some important mechanical properties were also compared to verify the suitability of the components. Final components produced are acceptable as per ISO standard UNI EN 20286-I (1995) and DIN16901. The results of study suggest that rapid silicon moulding process lies in ± 4.5 sigma (σ) limit as regards the dimensional accuracy of plastic components is concerned. This process ensures rapid production of pre-series technological prototypes and proof of concept at less production cost and time.

Wplyw zawartosci poroforu i warunkow wtryskiwania na wybrane wlasciwosci i stan powierzchni wyprasek z polipropylenu

Wplyw zawartosci poroforu i warunkow wtryskiwania na wybrane wlasciwosci i stan powierzchni wyprasek z polipropylenu

Integration of a fuzzy neural network and multi-objective genetic algorithm for optimisation of BLU light guide plate injection moulding parameters

Backlight module unit (BLU) is a key component of LCD, and thinning of the BLU light guide plate is the focus of development. Most light guide plates are manufactured using the injection moulding process. The experimental design in this study is the most common research approach applied in the setting of light guide plate parameters. However, the parameter interaction and system non-linearity can easily result in prediction errors of parameters. Meanwhile, since the optimal moulding conditions have not been achieved, the best effects of display illumination and brightness cannot be achieved. Hence, this study first applied the grey relational sorting method to determine the major control factors influencing the BLU light guide plate, and then built the approximate model of a fuzzy neural network, according to experimental planning samples, before using the multi-objective genetic algorithm to determine the optimal manufacturing parameter design. The results suggested that the process capability index Cpk value of the light guide plate X-axis size is improved from 0.43 to 1.56, and has stabilised product quality and enhanced process capability. This study proved that the prediction model of process optimisation, as obtained by using this research method, is effective.

The Effect of Preheating Temperature on the Microstructure and Properties of Copper by the Liquid Die Forging Technology

The copper specimen was fabricated through liquid die forging under different preheating temperature of mold condition. The effect of preheating temperature of mold on the microstructure, density, hardness, tensile strength and electrical conductivity were investigated. The results show that the crystal grain size was deceased firstly and then increased with the increasing of preheating temperature. Crystal grain was uniform and fine when the preheating temperature was 250 °C. The density of copper fabricated through liquid die forging was improved by about 5% comparing with that through static casting in metal mold. The hardness of copper fabricated through liquid die forging was HBS 85.2 when the preheating temperature was 250°C, which was higher than that at the rest preheating temperature conditions. The tensile strength was 288 MPa when the preheating temperature was 250°C. There was no obvious effect on the electrical conductivity under different preheating temperature.

3 차원 사출성형 해석을 통한 컴퓨터 마우스 제작용 이중사출성형 금형의 공정조건 결정

The objective of this study determine the molding conditions of a double-shot injection mold for fabricating a computer mouse using different materials, by performing three-dimensional injection molding analysis. In order to select the optical injection molding conditions, the effects of the injection time, the maximum injection pressure, the effect of packing time on the injection molding characteristics, and the product qualities were quantitatively examined. From the results of the injection molding analysis, the optimal injection molding conditions of the double-shot injection mold, which leads the molded product to the minimized shrinkage and deflection, were estimated. The results of the injection molding experiments, showed that an appropriate computer mouse can be fabricated using different materials when the identified optimal injection molding conditions are adopted.

Experimental Investigations for Silicon Moulding Solution of Plastic Components

The purpose of the present study is to experimentally investigate rapid moulding solutions for plastic components using silicon moulding technique. Starting from the identification of component, prototypes with two different type of plastic material were prepared under different vacuum moulding conditions. Measurements on the coordinate measuring machine helped in calculating the dimensional tolerances of the plastic components produced. Some important mechanical properties were also compared to verify the suitability of the components. The study highlighted the best settings of orientation and type of plastic material for the selected component from dimensional accuracy and economic point of view as rapid moulding solution for plastic components. Final components produced are acceptable as per IS standard UNIEN20286-I (1995). This process ensures rapid production of pre-series technological prototypes and proof of concept at less production cost and time.

Experimental determination and control of prepreg tack for automated manufacture

The automated tape laying (ATL) process has been examined and found to be sensitive to tack and stiffness properties of the prepreg material being laid. A comparison of existing aerospace and newly developed ATL prepreg tapes has revealed significant differences in tack response to temperature and feedrate. Examination of constituent resin rheology has found that tack, and the two observed failure modes, are somewhat dependent upon viscoelastic stiffness. Observation of temperature and feedrate response revealed a time–temperature superposition relationship. The Williams–Landel–Ferry equation was utilised to make predictions of the temperature response based on the feedrate response. Tack levels were stabilised over the feedrate range by making temperature adjustments. Results from the peel test, where mould conditions at lay-up were recreated, were found transferable to the ATL, where a suitable lay-up feedrate under ambient conditions was predicted.

An evaluation of the three-dimensional geometric shape of moulded bra cups

Bra cup moulding is currently a remarkable process in the production of seamless intimate apparel. The process is highly complex, time-consuming and error-prone due to the large variations of foam and lamination properties, cup styles and sizes, and geometric features of graduated padding. In particular, the three-dimensional (3D) geometric shape of foam cups is difficult to assess accurately because they are very soft and readily deform. In cases that involve fitting problems, shape modifications of the mould head and determination of the optimal moulding conditions have undergone repeated trials and errors. There is limited knowledge about the effects of foam properties and cup parameters in the controlling of moulding conditions. This study adopts a parameterization-based remesh algorithm method to evaluate the 3D shapes of the convex surface of scanned cup samples. The shape conformity of the cup is quantified in accordance to the corresponding mould head. In this respect, the moulding conditions that would achieve the most desirable geometric shapes of bra cups can be accurately and objectively demonstrated. Based on moulding experiments with 6 types of polyurethane (PU) foam materials, empirical equations that associate the cup shape conformity and the shape deviations from selected cup sectional curves are established. Through the use of non-linear regression models, the shape conformity of the moulded cups can be predicted by moulding conditions with reasonable accuracy. The shape conformity provides effective guidelines for quality assurance and improves production efficiency of bra cup moulding. Moreover, thermal-mechanical properties, such as compressive strain and softening temperature obtained from thermomechanical analysis (TMA) scans, provide a good understanding of cup shape conformity and determine the lowest moulding temperature at initial trails of the bra cup moulding process. Surprisingly, in pliable foams, the cup size does not have an apparent effect on the moulding conditions to achieve optimal cup shape conformity. The results reveal that the moulding conditions for sizes 34B and 34D could remain the same for pliable foam materials. Nevertheless, in the case of more rigid foams, a higher moulding temperature is required to achieve a desirable cup shape for size 34D as more energy is required for the heat-setting of foam materials with higher proportions of hard segments at the moulding of a larger cup size in anticipation of larger deformations.

Factores de risco e prevalência de asma e rinite em crianças em idade escolar em Lisboa

Aims A cross-sectional study was carried out with the objective of identifying nutrition habits and housing conditions as risk factors for respiratory problems in schoolchildren in Lisbon. Material and Methods Between October and December 2008, parents of 900 students of the basic schools of Lisbon were invited to answer a questionnaire of the International Study of Asthma and Allergies in Childhood Program (ISAAC). The response rate was 40%. Logistic regression was used in the analysis of results. Results The prevalence of asthma, allergic rhinitis and wheeze was 5.6%, 43.0% and 43.3%, respectively. Risk factors independently associated with asthma were wheezing attacks, and dry cough at night not related to common cold in the last 12 months. Wheezing crises were found to affect children daily activities. Risk factors for wheeze were hay fever and the presence of a pet at home. A risk factor for rhinitis was cough at night. The frequent consumption of egg was also associated with increased risk of rhinitis. Conclusion Contrarily to asthma, the prevalence of allergic rhinitis and wheeze increased in comparison with previous ISAAC studies. Wheezing attacks were associated with asthma and hay fever was identified as a risk factor of manifesting wheezing symptoms. Having pets at home was pointed out as a significant risk factor for rhinitis, but not smoking exposure, mould, plush toys, diet (except egg consumption), breastfeeding or other conditions.

Simulation of Thermoset Injection for Bulk Moulding Compounds (BMC)

This paper discusses about the simulation of the process of injection moulding for thermoset materials namely Bulk Moulding Compounds (BMC). BMC is a polyester resin based compound with glass fibre additives. In this paper a complex part was used to simulate and obtain the parameters for moulding BMC. Autodesk Moldflow Plastics Insight was used to run the simulation. Two main parameters i.e. Injection time and mould temperature were considered. Six different sets of parameters were used and the settings were optimized. The obtained optimized settings are 15.08 seconds and 145°C. The obtained parameters were then applied and the actual part was tested using an injection-moulding machine. After the simulation, changes were also made to the actual mould to improve the moulding conditions. Extra air vents were added at the problematic areas to ease the flow. There was an average variance of 7% which was thought to be acceptable as the simulation considers the ideal condition, where as there may be external factors such as the machine wear and tear during the actual moulding of the part. It can be said that the simulation was run successfully and tested during actual moulding.

S041021 軟磁性粉末射出成形体の充填密度に及ぼす材料および射出成形条件の影響([S04102]粉末成形とその評価(2))

S041021 軟磁性粉末射出成形体の充填密度に及ぼす材料および射出成形条件の影響([S04102]粉末成形とその評価(2))

Risk factors and prevalence of asthma and rhinitis among primary school children in Lisbon

AimsA cross-sectional study was carried out with the objective of identifying nutrition habits and housing conditions as risk factors for respiratory problems in schoolchildren in Lisbon. Material and methodsBetween October and December 2008, parents of 900 students of the elementary schools of Lisbon were invited to answer a questionnaire of the International Study of Asthma and Allergies in Childhood Program (ISAAC). The response rate was 40 %. Logistic regression was used in the analysis of results. ResultsThe prevalence of asthma, allergic rhinitis and wheeze was 5.6 %, 43.0 % and 43.3 %, respectively. Risk factors independently associated with asthma were wheezing attacks, and dry cough at night not related to common cold in the last 12 months. Wheezing crises were found to affect children daily activities. Risk factors for wheeze were hay fever and the presence of a pet at home. A risk factor for rhinitis was cough at night. The frequent consumption of egg was also associated with increased risk of rhinitis. ConclusionContrarily to asthma, the prevalence of allergic rhinitis and wheeze increased in comparison with previous ISAAC studies. Wheezing attacks were associated with asthma and hay fever was identified as a risk factor of manifesting wheezing symptoms. Having pets at home was pointed out as a significant risk factor for rhinitis, but not smoking exposure, mould, plush toys, diet (except egg consumption), breastfeeding or other conditions.

Elaboration of PIM feedstocks with 316L fine stainless steel powders for the processing of micro-components

The paper is concerned with the way to prepare feedstocks for powder injection moulding of fine stainless steel powders. The way to prepare adequate feedstocks is described, and injection moulding experiments are determined. The effects of powder volume loading, as well as mixing conditions are investigated and the results indicate that powder loading, injection moulding conditions and sintering kinetics largely influence the resulting shrinkage after sintering. Finally, the modelling and associated numerical simulations are used the help process design.

Low temperature induced defence gene expression in winter wheat in relation to resistance to snow moulds and other wheat diseases

Cold hardening of winter wheat at 2°C for 1–6wks increased resistance to the snow mould pathogens LTB, Typhula incarnata, and Microdochium nivale as well as to powdery mildew (Blumaria graminis f. sp. graminis) and stripe rust (Puccinia striiformis). Using microarrays and hardening of winter wheat for 0.25, 0.5, 1, 7, 21 and 49d, an upregulation of a wide range of stress-response genes that include defence-related and abiotic stress-related genes, transcription factors including several lipoxygenases and ethylene responsive factors, and WRKY genes was observed. For the majority of these genes, the upregulation occurred later in the 21–49d hardening treatments and coincided with the highest expression levels of snow mould resistance. Defence-related sequences were upregulated to a greater extent and were more numerous in the snow mould resistant line CI14106 compared to cold hardy DH+268. Transcript profiling of candidate defence and other stress-related genes under prolonged conditions at −3°C with or without snow mould infection showed that there was a decline in transcripts of the defence-related genes PR1.1b and NPR3 during the 12wks incubation. Additionally, 14d hardening was insufficient to permit full expression of the jasmonic acid synthesis gene, allene oxide synthase (AOS) and the fructan degrading enzyme β-fructofuranosidase compared the 42d hardening treatment. The snow mould resistant line CI14106 was able to maintain higher transcript levels of AOS for longer conditions compared to the susceptible line Norstar under artificial snow mould conditions. These results explain the nature of cold-induced resistance to snow moulds and provide direction on establishing selection criteria for improving resistance and cold tolerance in winter wheat.

The Impact of School Building Conditions on Student Absenteeism in Upstate New York

We investigated Upstate New York school building conditions and examined the associations between school absenteeism and building condition problems. We merged data from the 2005 Building Condition Survey of Upstate New York schools with 2005 New York State Education Department student absenteeism data at the individual school level and evaluated associations between building conditions and absenteeism at or above the 90th percentile. After adjustment for confounders, student absenteeism was associated with visible mold (odds ratio [OR]=2.22; 95% confidence interval [CI]=1.34, 3.68), humidity (OR=3.07; 95% CI=1.37, 6.89), poor ventilation (OR=3.10; 95% CI=1.79, 5.37), vermin (OR=2.23; 95% CI=1.32, 3.76), 6 or more individual building condition problems (OR=2.97; 95% CI=1.84, 4.79), and building system or structural problems related to these conditions. Schools in lower socioeconomic districts and schools attended by younger students showed the strongest associations between poor building conditions and absenteeism. We found associations between student absenteeism and adverse school building conditions. Future studies should confirm these findings and prioritize strategies for school condition improvements.

Low-velocity impact response of injection-moulded polypropylene plates – Part 2: Effects of moulding conditions, striker geometry, clamping, surface texture, weld line and paint

The low-velocity, low-energy impact response of a mineral and elastomer modified polypropylene was characterised by instrumented falling-weight impact testing of plates with annular clamping. Most of the impact tests were performed at −30 °C with incident impact velocities in the range 1.0–4.4 m/s, and with plate thicknesses in the range 2.0–3.9 mm. The following factors were investigated: moulding conditions (mould temperature, melt temperature, holding pressure), striker geometry, clamping, plate surface texture, melt flow weld lines and paint. The occurrence of brittle fracture was affected by all these factors, except the moulding conditions. Reducing the striker hemisphere diameter or changing to a flat striker induced brittle fracture. Removing the annular clamping led to a more brittle response. Plates with a weld line were more brittle than standard plates. The surface texture caused brittle fracture when the textured side was in tension under the striker. The paint induced brittle fracture at −30 °C, but no adverse effect of the paint was observed at 20 °C.

Home Environmental Factors Associated With Poor Asthma Control in Montreal Children: A Population-Based Study

Background. Home environmental exposures may aggravate asthma. Few population-based studies have investigated the relationship between asthma control in children and home environmental exposures. Objective: Identify home environmental exposures associated with poor control of asthma among asthmatic children less than 12 years of age in Montreal (Quebec, Canada). Methods. This cross-sectional population-based study used data from a respiratory health survey of Montreal children aged 6 months to 12 years conducted in 2006 (n = 7980). Asthma control was assessed (n = 980) using an adaptation of the Canadian asthma consensus report clinical parameters. Using log-binomial regression models, prevalence ratios (PRs) with 95% confidence intervals (95% CIs) were estimated to explore the relationship between inadequate control of asthma and environmental home exposures, including allergens, irritants, mold, and dampness indicators. Subjects with acceptable asthma control were compared with those with inadequate disease control. Results. Of 980 children with active asthma in the year prior to the survey, 36% met at least one of the five criteria as to poor control of their disease. The population's characteristics found to be related with a lack of asthma control were younger age, history of parental atopy, low maternal education level, foreign-born mothers, and tenant occupancy. After adjustments, children living along high-traffic density streets (PR, 1.35; 95% CI, 1.00–1.81) and those with their bedroom or residence at the basement level (PR, 1.30; 95% CI, 1.01–1.66) were found to be at increased risk of poor asthma control. Conclusions. Suboptimal asthma control appears to be mostly associated with traffic, along with mold and moisture conditions, the latter being a more frequent exposure and therefore having a greater public health impact.

Three-dimensional Fiber Orientation of FRTP Obtained by Injection Molding —Detailed Analyses on the Fiber Orientation of a Thin Plate at the exit of a Pinpoint Gate—

The detailed analyses were conducted on three-dimensional fiber orientation of thin FRTP plate with a pinpoint-gate at the center. To visualize the 3 D fiber orientation, X-ray transmission CT was used and the following conclusions were obtained.1) Owing to the change in flow direction from expanding flow in the filling stage to shear flow in the packing stage, the fiber orientation at the exit of the gate changes from concentric alignment to radial one.2) Molding conditions such as injection speed, mold temperature and resin temperature have slight influence on the fiber orientation.3) The development of shear flow is easily affected by plate thickness and gate dimension. Thinner plate thickness and smaller gate size bring about lower fiber orientation because of less shear flow development.

Flow Oscillations and Meniscus Fluctuations in a Funnel-Type Water Mold Model

Transient flows in a funnel-type continuous casting process model were studied experimentally to investigate the flow oscillations inside the mold and the meniscus fluctuations. A full-scale water model was used with dimensions of 2000 mm (length) × 1350 mm (width) × 100 mm (thickness). Particle image velocimetry (PIV) was employed to measure the flow oscillations. To minimize high shear flow errors near the submerged entry nozzle (SEN) exit, the window deformation technique was adopted. The meniscus levels were extracted by edge-detection image processing. Three types of SEN and two funnel thicknesses (180 mm and 220 mm) were tested to examine the flow characteristics under five flow rates (10, 20, 30, 40, and 50 m3/h). The vortex generation mechanism inside the mold was analyzed across the various mold conditions studied.