Aluminum Mold Research Articles

End-of-life carbon fiber/poly(phenylene sulfide) semipreg scraps from the aerospace industry: Towards a sustainable product

End-of-Life (EoL) carbon fiber (CF)/poly(phenylene sulfide) (PPS) semipreg scraps from the aerospace industry were used for the development of new products. The scraps were cut and placed randomly in aluminum molds, with and without continuous layers of semipreg, to obtain five different laminates processed by hot compression molding. The laminates were inspected by ultrasound, followed by cutting standardized test specimens using a CNC machine. Afterward, the laminates were evaluated for thermal (differential scanning calorimetry, DSC) and mechanical properties (tensile test and interlaminar shear strength, ILSS). The morphological characteristics of fracture surfaces were evaluated by scanning electron microscopy, SEM, and optical microscopy, OM. Ultrasound inspection indicated that four laminates showed the presence of voids, flaws, defects, and internal discontinuities, some very pronounced. However, the five laminates processed did not show differences in thermal stability. The size of the scraps and the direction of the CF contributed unintentionally so that two laminates presented tensile strength values 15 % lower than the reference laminate (822 MPa) and ILSS values (64 MPa) very close to the reference. The micrographs showed the ordering and positioning of the CF/PPS semipreg layers. The results were promising and could be considered as resources for developing new products through recycling processes.

On tailored microstructure in AA 2024 alloy during in-situ microwave casting

In the present study, application of microwave energy was explored for tailoring the microstructure in AA 2024 alloy through directional solidification route. Microwave transparent (alumina) and absorbing (graphite) mould materials were utilized to investigate the effect of microwave interaction (electric and magnetic field components) with AA 2024 alloy on microstructure evolution in terms of dendrite size distribution and formation of eutectic phase. Results showed more pronounced eutectic phase gradient was developed using alumina mould. On the other hand, a more uniform distribution of the eutectic phase and grain size was observed with graphite mould. The development of the eutectic phase gradient is attributed to the effective microwave interaction with the AA 2024 alloy melt during solidification. This is primarily associated with the formation of an additional flux at the solid-liquid (S/L) interface of the alloy under the effect of magnetic field and an enhancement in diffusion flux due to mass transport caused by electric field component of microwave. Formation of AlCu, Al2Cu, and Al2CuMg intermetallic phases in both alumina and graphite mould casts was confirmed. Significantly higher hardness was observed at the higher eutectic phase sites within the alumina mould cast, whereas graphite mould casts exhibited better tensile properties.

Fabrication of Hybrid Epoxy Composites (Joint Compound Adhesive) for Aluminum Substrate Applications and Their Evaluation for Mechanical Properties.

This research endeavor deals with the development of an epoxy hybrid nanocomposite using aliphatic diglycidyl ether of a bisphenol A (DGEBA) epoxy matrix. The formulation used the stoichiometric ratio of the curing agent and incorporated nanopigments such as zirconium and silica, along with other microfillers. We incorporated Zr and SiO2 nanoparticles and various other additives in the epoxy matrix and ensured homogeneous dispersion by using sonication methodology along with silane as a coupling agent. Aluminum molds were utilized to fabricate dumbbell-shaped ASTM standard samples for the testing of mechanical properties. The adhesive properties were evaluated through standard lap shear tests. Fourier transform infrared spectroscopy was utilized to analyze the cross-linking reaction of the epoxy moiety and the polyamidoamine adduct curing agent. Further characterization using field emission scanning electron microscopy, energy-dispersive spectroscopy, and high-resolution transmission electron microscopy confirmed the presence and uniform dispersion of the fillers and nanopigments. The results showed good enhancements in ultimate tensile strength, yield strength, and elastic modulus of 95.3, 162.1, and 425.4%, respectively, compared to formulations using only SiO2. The addition of ZrO2 and SiO2, along with various microfillers, such as talc and aluminum silicate, led to significant improvements in the mechanical properties. This study demonstrates the synergistic efficiency of combining SiO2 and ZrO2 along with microfillers, such as talc and aluminum silicate, in epoxy resin for diverse applications in the construction industry, where mechanical strength and substrate adhesion are crucial.

Investigating the effect of deicing parameters using high-pressure water jet

Maritime operations are impacted by ice accretion on decks, bulkheads, and offshore structures during the winter or in extremely frigid climates. In most cases, the traditional method of deicing maritime vessels is human labor, which requires enormous effort and lengthy hours for unsatisfactory results, particularly when the ice adhesion strength is high. This study experimentally examined combined effects of operational parameters, including operating pump pressure, nozzle geometry, water jet temperature, standoff distance, and time of cut, on the depth and width of a cut through an ice block. In comparison to other parameters, the influence of nozzle geometry on both the width and depth of cut was found to be more significant, with R-squared values of 85% and 62% respectively. Increasing the depth and width of the cut facilitated the delamination and disintegration of ice from an aluminum mold. This indicates that water jet deicing on maritime vessels could be effective, therefore achieving the objective of this study. The optimization of operational parameters is used to develop a cuttability chart for various thicknesses of accumulated ice on marine vessels.

Machinability performance of different fiber orientations of roll wrapped CFRP pipes

AbstractIntegrating fiber reinforcement plastics (FRP) materials into the industry plays a key role especially for pipes. However, due to the production methods of CFRP pipes, surface finishing processes are inevitable at the end of production. Despite the widespread use of CFRP materials, the predominant focus in the literature has been on their mechanical performance. This study aims to contribute to the limited research on the machinability of CFRP materials. In this context, the turning machining process for CFRP pipes was experimentally investigated in the present study. For this purpose, carbon fiber pipes with an inner diameter of 30 mm and an outer diameter of 60 mm were produced and subjected to computer numerical control (CNC) turning. First, a cylindrical aluminum pipe is used as a mold to manufacture CFRP pipes. Unidirectional (UD) carbon fabrics were wrapped on these aluminum molds. Shrink tape was used to enhance the surface smoothness and required pressure to prevent delaminating of the end product during the process. UD carbon fabrics are wrapped on to the mold at the selected angles (0°, 45°, and 90°) and the CFRP pipe specimens were manufactured using epoxy matrix. Pipes were processed on CNC lathe at 120, 160, 200 rev/min speeds and f 0.4 mm/rev feed rate. The surfaces of the machined specimens were measured with a microscope and a surface roughness device. On the other hand, wear on the tools was observed after the process.Highlights CFRP pipes were produced with different fibre orientations, i.e., 0°, 45°, and 90°. All CFRP pipes are made under equal conditions and cured at 80°. Turning of CFRP pipes was examined under dry environments. Performance criteria: surface roughness, temperature, tool wear, and chip formation were explored. 45° fibre angles CFRP pipes showed the best machinability performance.

Effect of Mold Materials Used During Hot Embossing on Feature Fidelity for Microfabrication in Cyclic Olefin Polymer (COP) Substrate

During the transition from research to market, the fabrication of microfluidic devices in thermoplastic substrates is inevitable. For short production runs of several hundred products, hot embossing is the typical method before moving on to a typically more expensive injection molding process for higher production volumes. In this work, we investigated the effect of mold material used during hot embossing on feature fidelity for microfabrication in cyclic olefin polymer (COP) substrate. Specifically, we designed a simple flow-focusing microfluidic device and fabricated three different molds using silicon wafer by deep reactive ion etching (DRIE), aluminum filled high temperature epoxy by soft lithography and aluminum by CNC milling. We performed hot embossing experiments with 2mm thick COP substrates and these three different molds using automatic bench top Carver hot press. Finally, we characterized the hot embossed substrates by optical and scanning electron microscopy. Fabrication results demonstrate that the mold material plays a big role in feature fidelity. Among the mold materials used, silicon substrate performed the worst based on defects after demolding. Epoxy and aluminum molds were similar in terms of microfabricated feature defects in the substrate which could be mostly attributed to their coefficient of thermal expansion (CTE). A mold material with a CTE closer to the thermoplastic will result in much better feature fidelity.

In Situ Stereo Digital Image Correlation with Thermal Imaging as a Process Monitoring Method in Vacuum-Assisted Thermoforming

This experimental study probes the dynamic behaviour of a 3 mm ABS sheet during positive mould vacuum-assisted thermoforming. In this process, the sheet undergoes large and fast deformations caused by the applied vacuum and mechanical stretching by the mould. The objective is to elucidate the complexities of these large, rapid, and non-isothermal deformations. The non-isothermal conditions are caused by the radiative heating of the sheet, convective heat loss to the surrounding air, and conductive heat transfer from the sheet to the mould. By utilizing stereo digital image correlation (DIC) in tandem with thermal imaging, the present study accurately maps the occurring displacement, strain, and strain rate field in relation to real-time temperature variation in the material. The study progresses to observe the ABS material from the moment it contacts the mould until it conforms to a positive 250 mm diameter semi-sphere cast aluminum mould. The DIC methods are validated by comparing thickness values derived from DIC’s principal strain directions to ultrasonic thickness gauge readings. This knowledge not only broadens the understanding of the thermo-mechanical behaviour of the material but also aids in optimizing process parameters for improved thickness uniformity in thermoformed products.

Review of: "Magnetic nanowires such as cobalt, nickel, iron and alloys can be made by electroaccumulation and spontaneous accumulation on an anodic aluminum oxide mold, and the magnetic properties of cobalt nanowire arrays such as coercive force"

Review of: "Magnetic nanowires such as cobalt, nickel, iron and alloys can be made by electroaccumulation and spontaneous accumulation on an anodic aluminum oxide mold, and the magnetic properties of cobalt nanowire arrays such as coercive force"

The effect of characteristics of the mold with and without pin fins on the cooling profile in rotomolding sistem by FEM

In the rotomolding processes, the cooling stage is important, which affects significantly the productivity and quality of the final product. Therefore, in this work, a computer simulation was performed, studying the effect of the pin fins on the mold in the cooling phase in the rotomolding system, thus, steel and aluminum molds with and without pin fins were considered. In this work we had the following results, according to the optimization process, due to the high conductivity and low density of aluminum, it was verified that less pin fins were needed around the mold aluminum than for steel, but the length of the pin fins was greater for aluminum; in addition, the mold with fins had a faster cooling than the mold without fins; meanwhile, the use of appropriately sized fins significantly reduces the cooling time, nevertheless, as has been observed that the increasing or decreasing the fin number, the cooling profile is very little affected. However, the variation of the conviction coefficient applied to the external surfaces was also investigated, but the behavior of the fins are more efficient when the convection coefficient is higher so improving productivity. Finally, he characteristic of the mold material was also examined, as the steel mold with fins has a sharper cooling compared to the same material without fins, however, the aluminum was more efficient, because the cooling process was faster in molds of aluminum with fins. Emphasizing, the numerical simulation can be satisfactorily applied in the industrial process of rotomolding, of a simplified manner and qualitatively, promoting growth in production and reducing so the costs considerably associated with the production.

Using Sensor Fusion and Machine Learning to Distinguish Pedestrians in Artificial Intelligence-Enhanced Crosswalks

Pedestrian safety is a major concern in urban areas, and crosswalks are one of the most critical locations where accidents can occur. This research introduces an intelligent crosswalk, employing sensor fusion and machine learning techniques to distinguish the presence of pedestrians and drivers. Upon detecting a pedestrian, the system proactively activates a warning light signal. This approach aims to quickly alert nearby people and mitigate potential dangers, thereby strengthening pedestrian safety. The system integrates data from radio detection and ranging sensors and a magnetic field sensor, using a hierarchical classifier. The One-Class support vector machine algorithm is used to classify objects in the radio detection and ranging data, while fuzzy logic is used to filter out targets from the magnetic field sensor. Additionally, this work presents a novel method for the manufacture of the road signaling system, using mixtures of resins, aggregates, and reinforcing fibers that are cold-injected into an aluminum mold. The mechanical, optical, and electrical characteristics were subjected to standardized tests, validating its autonomous operation in real-world conditions. The results revealed the system’s effectiveness in detecting pedestrians with a 99.11% accuracy and a 0.0% false-positive rate, marking a substantial improvement over the previous fuzzy logic-based system with an 81.33% accuracy. Attitude testing revealed a significant 33.33% reduction in pedestrian erratic behavior and a substantial decrease in driver speed (32.83% during the day and 70.6% during the night) compared to conventional crossings. Consequently, this comprehensive work offers a unique solution to pedestrian safety at crosswalks by showcasing the potential of machine learning techniques, particularly the One-Class support vector machine algorithm, in advancing road safety through precise and reliable pattern recognition.

Impact behaviour of tunnel lining assembled from non-planar interlocking steel fibre reinforced concrete bricks

In this study, a new design of tunnel lining assembled from non-planar interlocking segments was developed and tested. The new tunnel segment is made of steel fibre reinforced concrete (SFRC), and it has six symmetrical side surfaces with a concave-convex topology, which can prevent the movement of each element in the interlocked tunnel. A series of lab-scale drop weight tests were conducted to investigate the performance of the interlocking SFRC tunnel specimen under impact. A special aluminium mould was designed to cast the developed tunnel segments, and a novel testing frame was developed to allow the drop hammer to hit on the inner surface of the tunnel specimen. The peak impact force, the displacement of the drop hammer and the failure pattern of the interlocking SFRC brick were measured and analysed, considering the influences of hammer dropping height and confining load on the dynamic behaviour of the interlocking SFRC tunnel specimen.

Process optimization for short carbon fiber polyetherimide composite mold

With the high precision requirements and the trend of large-scale composite parts, the development of composite molds is imminent. The short carbon fiber (SCF) composite mold is mainly prepared by the technological process flow of composite sheet injection, the bonding of composite plates, and machining. However, the current process optimization method has not matured adequately, and there are still many shortcomings, for example, low precision and high cost. In this paper, the optimization method of SCF/polyetherimide (PEI) composite molds is proposed. Many experiments have been conducted, and the results show that the coefficient of thermal expansion of composite samples can be effectively reduced and the mechanical properties can be improved by optimizing the SCF weight ratio and carbon fiber length. The bonding strength of composite joints in a high-temperature environment can be improved by optimizing the bonding process parameters and modification by carbon nanotubes. Based on the above optimization method, the SCF/PEI composite mold is prepared, and the C-shaped beam composite part is fabricated by using this mold. Compared with the part made by aluminum mold, the shape accuracy of the C-shaped beam composite part is proven high through digital measurement technology.

FABRICACIÓN Y CARACTERIZACIÓN DE UN PASO DE PEATONES INTELIGENTE PARA MEJORA DE LA SEGURIDAD VIAL

Road signalling systems help to improve attention and reduce speed while driving. However, most solutions are not commercially available, require expensive infrastructure, lack intelligence, or do not cover 100% of road users. To reduce this gap, this work presents a speed bump with intelligent light signalling that detects both pedestrians and vehicles on zebra crossings. The system is made up of low-cost prefabricated nodes with maturity level TRL8 that can be adapted to any type of road. As main novelty, this paper describes the materials and methods used to manufacture speed bumps with mixtures of resins, aggregates and reinforcing fibers injected cold on aluminium mould. As a result of the tests, a compromise between hardness, resistance and elasticity with IP68 rating was reached. This makes it possible to ensure the mechanical and optical operation of the system without the need for external power supplies and with an acceptable manufacturing cost. Key Words: speed reducer, road safety, pedestrian crossing, intelligent system, mechanical characterization

Preparation of antireflection structures with heat resistance by nanoimprinting using anodic porous alumina molds

Polysiloxane antireflective structures composed of tapered nanopillar arrays were prepared by nanoimprinting using anodic porous alumina molds with tapered pores. Because polysiloxane is a heat-resistant material, the resulting tapered nanopillar array structures were maintained even after heat treatment at 200 °C. In addition, no significant changes in antireflection properties were observed before and after heat treatment at 200 °C. These results indicate that the polysiloxane nanopillar arrays obtained in this study can be applied as heat-resistance antireflection structures.

Fabrication of Moth-Eye Structures with Precisely Controlled Shapes by Nanoimprinting Using Anodic Porous Alumina Molds

An anodic porous alumina mold with tapered pores, which can be used to form moth-eye structures, was formed by repetitions of anodization and etching. It was shown that the controllability of the pore shape of the anodic porous alumina mold improved with the number of repetitions of anodization and etching. However, it was found that even when the total anodization time or anodic charge (electrical current × time) was kept constant, the thickness of anodic films was not constant because the total etching time varied. This is because the etching of the anodic porous alumina mold not only increases the pore size but also reduces the thickness of the barrier layer so that pore growth proceeds after the barrier layer is re-formed during re-anodization. Therefore, it was found that if anodization is performed with the additional anodic charge required to re-form the barrier layer, an anodic porous alumina mold with tapered pores and uniform film thickness can be produced even if the etching time is varied. Nanoimprinting using the resulting anodic porous alumina mold was shown to form a moth-eye structure with a reflectance of less than 0.1% over the entire visible light range.

Sensitivity Analysis and Multi-Objective Optimization Strategy of the Curing Profile for Autoclave Processed Thick Composite Laminates.

To mitigate the risk of manufacturing defects and improve the efficiency of the autoclave-processed thick composite component curing process, parameter sensitivity analysis and optimization of the curing profile were conducted using a finite element model, Sobol sensitivity analysis, and the multi-objective optimization method. The FE model based on the heat transfer and cure kinetics modules was developed by the user subroutine in ABAQUS and validated by experimental data. The effects of thickness, stacking sequence, and mold material on the maximum temperature (Tmax), temperature gradient (ΔT), and degree of curing (DoC) were discussed. Next, parameter sensitivity was tested to identify critical curing process parameters that have significant effects on Tmax, DoC, and curing time cycle (tcycle). A multi-objective optimization strategy was developed by combining the optimal Latin hypercube sampling, radial basis function (RBF), and non-dominated sorting genetic algorithm-II (NSGA-II) methods. The results showed that the established FE model could predict the temperature profile and DoC profile accurately. Tmax always occurred in the mid-point regardless of laminate thickness; the Tmax and ΔT increased non-linearly with the increasing laminate thickness; but the DoC was affected slightly by the laminate thickness. The stacking sequence has little influence on the Tmax, ΔT, and DoC of laminate. The mold material mainly affected the uniformity of the temperature field. The ΔT of aluminum mold was the highest, followed by copper mold and invar steel mold. Tmax and tcycle were mainly affected by the dwell temperature T2, and DoC was mainly affected by dwell time dt1 and dwell temperature T1. The multi-objective optimized curing profile could reduce the Tmax and tcycle by 2.2% and 16.1%, respectively, and maintain the maximum DoC at 0.91. This work provides guidance on the practical design of cure profiles for thick composite parts.

Designing vent holes for thermoforming tooling produced via fused deposition modeling

Vent holes in thermoforming tooling are traditionally round and run perpendicular to the tool surface, as this is easy to produce via drilling and minimizes surface imperfections. This geometry should be reevaluated when producing tooling via fused deposition modeling (FDM). FDM offers thermoformers the possibility of lower tool cost and reduced lead-time compared to traditional aluminum molds. With FDM it is easier to create vent holes, even very small ones, in difficult-to-access locations. This is especially true if the holes have a rectangular cross section and lie parallel to the build plane. This alternative geometry requires modified rules to estimate the required number of holes and the size of dimple on the final part created by the vent hole during forming. In addition, FDM will produce holes with a very rough surface finish, potentially impeding flow. Computational fluid dynamics was used to show that this concern is unwarranted in practice. Finally, the Markforged Mark 2 printer was used to produce test holes, and their suitability for thermoforming is discussed.

The practical process of manufacturing poly(methyl methacrylate)-based scaffolds having high porosity and high strength

Poly(methyl methacrylate) (PMMA)-based scaffolds have been produced using the granule casting method with grain sizes M80–100 and M100-140. The novelty of this study was the application of the cold-cutting method (CCm) to reduce the PMMA granule size. PMMA granule shape, granule size (mesh), and sintering temperature were the primary variables in manufacturing PMMA scaffolds. CCm was applied to reduce the granule size of commercial PMMA, which was originally solid cylindrical, by lowering the temperature to 3.5 °C, 0 °C, and-8.3 °C. PMMA granules that had been reduced were sieved with mesh sizes M80–100 and M100-140. Green bodies were made by the granule casting method using an aluminum mold measuring 8 × 8 × 8 mm3. The sintering process was carried out at temperatures varying from 115 °C to 140 °C, a heating rate of 5 °C/min, and a holding time of 2 h, the cooling process was carried out in a furnace. The characterization of the PMMA-based scaffolds' properties was carried out by observing the microstructure with SEM, analyzing the distribution of pore sizes with ImageJ software, and testing the porosity, the phase, with XRD, and the compressive strength. The best results from the overall analysis were the M80-100 PMMA scaffold treated at a sintering temperature of 130 °C with compressive strength, porosity, and pore size distribution values of 8.2 MPa, 62.0%, and 121–399 μm, respectively, and the M100-140 one treated at a sintering temperature of 135 °C with compressive strength, porosity, and pore size distribution values of 12.1 MPa, 61.2%, and 140–366 μm, respectively. There were interconnected pores in the PMMA scaffolds, as evidenced by the SEM images. There was no PMMA phase change between before and after the sintering process.

Experimental study of GFRP stiffened plates with and without large opening under combined axial and pressure loading

GFRP stiffened panels forms the basic component of ship hulls, decks, submarines, offshore oil platforms etc., GFRP stiffened panels used in ship hulls and decks are subjected to axial loading due to buoyancy and pressure loading due to cargo. GFRP stiffened plate dimensions considered in this study are the scaled down dimensions of a cargo ship. Aluminium moulds with and without opening are fabricated for casting GFRP stiffened panels. GFRP stiffened panels with integral stiffeners are manufactured using hand lay-up process. A unique lay-up pattern was adopted to achieve the monolithic behaviour of stiffeners and plate. Fabrication of GFRP stiffened panels by manual hand layup process leads to formation of indentations. These imperfections are determined using the LVDTs attached to imperfection measurement setup. The measured imperfections are compared with the allowable imperfection values available for steel in BS 5400, because limiting imperfection values are not available for FRP. Openings are necessary for access and maintenance in ship hulls, decks etc. The presence of openings can lead to loss in strength and stiffness of the GFRP stiffened panels. In this study, GFRP stiffened panels with and without opening are tested for different combinations of axial and pressure loading. Axial loads are applied using two hydraulic jacks and measured using two load cells which are fabricated to prevent eccentricity while applying axial load. Pressure loads are applied using inflatable air balloons with and without opening fabricated for this study. Load capacity, failure strain, failure patterns of GFRP stiffened panels under different load combinations are presented. Failure locations of GFRP stiffened panels with and without opening various load combinations are discussed. Reduction in load capacity, span to deflection ratio and loss in stiffness due to opening is calculated.

Flat and roll-type translucent anodic porous alumina molds anodized in oxalic acid for UV nanoimprint lithography

Transparent anodic porous alumina mold for photo-nanoimprinting.