Zeitschriftenartikel: „Out-Of-Autoclave Consolidation“

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Centea, T., und P. Hubert. „Out-of-autoclave prepreg consolidation under deficient pressure conditions“. Journal of Composite Materials 48, Nr. 16 (08.07.2013): 2033–45. http://dx.doi.org/10.1177/0021998313494101.

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Shaik, Yousuf Pasha, Jens Schuster und Naresh Kumar Naidu. „High-Pressure FDM 3D Printing in Nitrogen [Inert Gas] and Improved Mechanical Performance of Printed Components“. Journal of Composites Science 7, Nr. 4 (10.04.2023): 153. http://dx.doi.org/10.3390/jcs7040153.

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Fundamentally, the mechanical characteristics of 3D-printed polymeric objects are determined by their fabrication circumstances. In contrast to traditional polymer processing processes, additive manufacturing requires no pressure during layer consolidation. This study looks at how a high-pressure autoclave chamber without oxygen affects layer consolidation throughout the fused deposition modelling process, as well as the mechanical qualities of the products. To attain high strength qualities for 3D-printed components such as injection-molded specimens, an experimental setup consisting of a 3D printer incorporated within a bespoke autoclave was designed. The autoclave can withstand pressures of up to 135 bar and temperatures of up to 185 °C. PLA 3D printing was carried out in the autoclave at two different pressures in compressed air and nitrogen atmospheres: 0 bar and 5 bar. Furthermore, injection molding was done using the same PLA material. Tensile, flexural, and Charpy tests were carried out on samples that were 3D printed and injection molded. In nitrogen, oxidation of the environment was prevented by autoclave preheating before printing, and autoclave pressure during printing considerably promotes layer consolidation. This imprinted mechanical strength on the 3D-printed items, which are virtually as strong as injection-molded components.

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Shaik, Yousuf Pasha, Jens Schuster, Harshavardhan Reddy Katherapalli und Aarif Shaik. „3D Printing under High Ambient Pressures and Improvement of Mechanical Properties of Printed Parts“. Journal of Composites Science 6, Nr. 1 (05.01.2022): 16. http://dx.doi.org/10.3390/jcs6010016.

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Contrary to other polymer processing methods, additive manufacturing processes do not require any pressure during the consolidation of layers. This study investigates the effect of high ambient pressure on the consolidation of layers during the FDM process and their analysis of mechanical properties. An experimental setup was arranged, consisting of a 3D printer integrated into a customized Autoclave, to achieve high strength properties for 3D printed parts as like injection-molded specimens. The autoclave can maintain 135 bar of pressure and a maximum temperature of 185 °C. 3D printing with PLA was carried out at 0 bar, 5 bar, and 10 bar. Tensile, flexural, and Charpy tests were conducted on printed specimens, and the effect of pressure and temperature on 3D-printed samples were analyzed. It could be shown that autoclave preheating before printing and autoclave pressure during printing improves the consolidation of layers immensely. The pressure inside the autoclave provokes a more intimate contact between the layer surfaces and results in higher mechanical properties such as yield strength, Young’s modulus, and impact strength. The properties could be raised 100%.

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Saenz-Castillo, Diego, María I. Martín, Vanessa García-Martínez, Abhiram Ramesh, Mark Battley und Alfredo Güemes. „A comparison of mechanical properties and X-ray tomography analysis of different out-of-autoclave manufactured thermoplastic composites“. Journal of Reinforced Plastics and Composites 39, Nr. 19-20 (07.05.2020): 703–20. http://dx.doi.org/10.1177/0731684420924081.

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Three different out-of-autoclave manufacturing processes of CF/poly-ether-ether-ketone thermoplastic composites were characterized, including innovative laser-assisted automated fibre placement with in situ consolidation. Characterization techniques included differential scanning calorimetry, ultrasonic non-destructive testing and matrix digestion, in addition to 3D X-ray microcomputed tomography to investigate the void distribution, size and shape. The results revealed that in situ consolidation process can lead to the accumulation of large voids between the upper layers. Interlaminar shear, in-plane shear, tensile and flexure testing were used for mechanical evaluation. A reduction in the mechanical properties was observed for in situ consolidation laminates when compared to the other out-of-autoclave methods. The drop in mechanical properties of in situ consolidation laminates was mainly attributed to the differences found in void distribution and size. Optimization of processing parameters along with higher quality prepreg raw material could be of assistance for the improvement of mechanical properties of in situ consolidation structures.

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Helmus, Rhena, Timotei Centea, Pascal Hubert und Roland Hinterhölzl. „Out-of-autoclave prepreg consolidation: Coupled air evacuation and prepreg impregnation modeling“. Journal of Composite Materials 50, Nr. 10 (24.06.2015): 1403–13. http://dx.doi.org/10.1177/0021998315592005.

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Drakonakis, Vasileios M., James C. Seferis und Charalambos C. Doumanidis. „Curing Pressure Influence of Out-of-Autoclave Processing on Structural Composites for Commercial Aviation“. Advances in Materials Science and Engineering 2013 (2013): 1–14. http://dx.doi.org/10.1155/2013/356824.

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Autoclaving is a process that ensures the highest quality of carbon fiber reinforced polymer (CFRP) composite structures used in aviation. During the autoclave process, consolidation of prepreg laminas through simultaneous elevated pressure and temperature results in a uniform high-end material system. This work focuses on analyzing in a fundamental way the applications of pressure and temperature separately during prepreg consolidation. A controlled pressure vessel (press-clave) has been designed that applies pressure during the curing process while the temperature is being applied locally by heat blankets. This vessel gives the ability to design manufacturing processes with different pressures while applying temperature at desired regions of the composite. The pressure role on the curing extent and its effect on the interlayer region are also tested in order to evaluate the consolidation of prepregs to a completely uniform material. Such studies may also be used to provide insight into the morphology of interlayer reinforcement concepts, which are widely used in the featherweight composites. Specimens manufactured by press-clave, which separates pressure from heat, are analytically tested and compared to autoclaved specimens in order to demonstrate the suitability of the press-clave to manufacture high-quality composites with excessively reduced cost.

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Mahmood, Amjed Saleh, John Summerscales und Malcolm Neil James. „Resin-Rich Volumes (RRV) and the Performance of Fibre-Reinforced Composites: A Review“. Journal of Composites Science 6, Nr. 2 (10.02.2022): 53. http://dx.doi.org/10.3390/jcs6020053.

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This review considers the influence of resin-rich volumes (RRV) on the static and dynamic mechanical and physical behaviour of fibre-reinforced composites. The formation, shape and size, and measurement of RRV in composites, depending upon different fabric architectures and manufacturing processes, is discussed. The majority of studies show a negative effect of RRV on the mechanical behaviour of composite materials. The main factors that cause RRV are (a) the clustering of fibres as bundles in textiles, (b) the stacking sequence, (c) the consolidation characteristics of the reinforcement, (d) the resin flow characteristics as a function of temperature, and (e) the composite manufacturing process and cure cycle. RRV are stress concentrations that lead to a disproportionate decrease in composite strength. Those who are considering moving from autoclave consolidation to out-of-autoclave (OOA) processes should be cautious of the potential effects of this change.

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Shaik, Yousuf Pasha, Jens Schuster, Aarif Shaik, Mustafa Mohammed und Harshavardhan Reddy Katherapalli. „Effect of Autoclave Pressure and Temperature on Consolidation of Layers and Mechanical Properties of Additively Manufactured (FDM) Products with PLA“. Journal of Manufacturing and Materials Processing 5, Nr. 4 (27.10.2021): 114. http://dx.doi.org/10.3390/jmmp5040114.

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In additive manufacturing technologies, fused deposition modelling (FDM) is continuing its advancement from rapid prototyping to rapid manufacturing. However, effective usage of FDM is not performed due to the poor mechanical properties of the 3D-printed components. This drawback restricts their usage in many applications. Much research, such as reinforcing 3D-printed parts with fibers, changing printing parameters (infill density, infill concentration, extrusion temperature, nozzle diameter, layer thickness, raster angle, etc.) are aimed to increase the mechanical properties of 3D-printed parts. This research paper aims to investigate the effect of pressure and temperature on the mechanical properties and consolidation of layers of 3D-printed PLA (Polylactic Acid). Post-treatment was done using a customized autoclave. Autoclave has the capability to maintain 185 °C and 135 bar pressure. Three-dimensional-printed specimens were manufactured using the FDM process with two patterns. Later, the specimens were subjected to various post-treatment processes, then followed with testing and analysis of mechanical properties. Post-treatment process carried out by placing them in an autoclave at certain pressure and temperature conditions. To investigate the repeatability and tolerances, the test series includes a minimum of four to six test specimens. The results indicate that the concentric pattern yields the most desirable tensile, impact, and flexural strength due to the alignment of deposited rasters and better consolidation of layers with the loading direction. The pressure and temperature of the autoclave has a positive effect on the PLA samples, which helped them to reorganize the structure, hence strength properties were enhanced. The test results also compared with injection-molded samples for better understating.

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Helmus, R., R. Hinterhölzl und P. Hubert. „A stochastic approach to model material variation determining tow impregnation in out-of-autoclave prepreg consolidation“. Composites Part A: Applied Science and Manufacturing 77 (Oktober 2015): 293–300. http://dx.doi.org/10.1016/j.compositesa.2015.03.021.

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Rizzolo, Robert, Daniel Walczyk, Jaron Kuppers, Daniel Montoney und Richard Galloway. „Rapid consolidation and curing of advanced composites using electron beam irradiation“. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 233, Nr. 4 (28.04.2018): 1168–81. http://dx.doi.org/10.1177/0954405418769950.

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A low-cost, low-waste manufacturing method for advanced thermoset composite parts could improve market penetration of composites compared to other engineering materials such as aluminum or steel. Such a method could combine some of the new trends in composites manufacturing such as resin infusion (eliminates need for prepreg), out-of-autoclave consolidation, and snap curing. The feasibility of a hybrid process with these characteristics has been demonstrated by uniting liquid composite molding, resin curing by electron beam irradiation, and high pressure consolidation with specialized elastomeric tooling. To demonstrate feasibility, a mold set was designed to make flat, square four-ply woven carbon fiber parts by (1) vacuum-infusing dry preforms with an electron beam–curable epoxy resin in minutes, (2) applying 690 kPa of uniform pressure and consolidating in seconds using an elastomer-faced specialized elastomeric tooling tool and simple hydraulic press, and (3) curing in seconds using a 3 MeV electron beam source. To better understand how various process parameters affect part performance, parameters are varied in a simple design of experiments, and flexural strength and stiffness, thickness distribution, fiber and void volume fractions, surface roughness, and cross-sectional characteristics (via microscopy) are measured and compared.

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Heil, Joseph P., Mark A. Wadsworth, Kerrick R. Dando, Ron E. Jones, Matt Tymes, Sam J. Slater, Rodney E. Bahr und Bryan T. Bearden. „Thermoplastic Composite Rate Enhanced Stiffened Skin: A Case Study“. SAMPE JOURNAL 59, Nr. 6 (November 2023): 9–18. http://dx.doi.org/10.33599/sj.v59no6.01.

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Spirit AeroSystems is developing a thermoplastic technology demonstrator featuring an out of autoclave fabrication approach. Furthermore, the intent is to demonstrate the capability in the United States and preferably at our own domestic facility. The chosen configuration is a fuselage skin panel about 1.2 m wide and 2.2 m long with five stringers and four frames. Laser assisted thermoplastic Automated Fiber Placement (AFP) is used to manufacture the skin; stringers are stamp formed, and frames used two fabrication paths: stamp forming and oven consolidation. Co-Fusion simultaneously consolidates the skin and welds stringers to the skin followed by a separate frame welding process.

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Varkonyi, Balazs, Jonathan P. H. Belnoue, James Kratz und Stephen R. Hallett. „Predicting consolidation-induced wrinkles and their effects on composites structural performance“. International Journal of Material Forming 13, Nr. 6 (16.11.2019): 907–21. http://dx.doi.org/10.1007/s12289-019-01514-2.

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AbstractThe majority of high-performance composite parts are nowadays designed using advanced numerical simulations that are able to accurately predict a part’s strength and deformation, providing that the internal ply architecture and exact fibre orientation are known with sufficient accuracy. However, most parts have some deviation of the fibre orientation from the ‘as-designed’ geometry, leading to the simulation overestimating the component’s strength. Up until recently, the advancement of the process simulation tools has not been sufficient to allow knowledge of this fibre deviation before any part has been manufactured, thus leading to overly conservative designs and costly experimental optimisation of the manufacturing process to reduce fibre path defects. This results in additional cost, waste of material and increased fuel consumption (due to the unnecessary weight of the components). This paper shows how state-of-the-art composite manufacturing simulations of the autoclave consolidation process can predict and help to mitigate against out-of-plane wrinkle formation in components made from toughened UD prepregs and thus raise confidence in failure analyses predictions. The industry relevant case of a stepped laminate is used as an example. Model predictions for the internal ply geometries are quantitatively compared to micrograph images of real samples. It is then shown how the input of the simulated ply architecture helps improving the accuracy of the failure simulations.

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Link, Tobias, Philipp Rosenberg und Frank Henning. „Prediction of Gaps in Automated Tape Laying and Their Influence on Porosity in Consolidated Laminates“. Journal of Composites Science 6, Nr. 7 (15.07.2022): 207. http://dx.doi.org/10.3390/jcs6070207.

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An efficient way to reduce direct operating costs in aerospace applications is to lower the overall weight. In this context, thermoplastic composites offer a high potential for weight reduction. However, their application requires time and cost-optimized process technologies. Thermoplastic tape laying with subsequent out-of-autoclave consolidation represents such a process technology. Typical process chains consist of several automated steps that can influence the component’s quality. Hence, a cross-process approach is applied to identify relevant process parameters. This paper focuses on minimizing the gaps between parallel-placed tapes and thereby reducing their influence on the laminate’s porosity. A geometrical model is developed and validated to predict the maximum gap sizes for a tape-laying process as a function of process accuracy, material accuracy, and process parameters. Based on this, a methodological approach is presented to minimize the influence of gaps on porosity. It is validated using automated tape laying and a novel low-pressure consolidation process. The findings make an important contribution to understanding the development of porosity along the process chain for the manufacture of thermoplastic composites for aerospace applications. It can be shown that the approach enables the prediction of gap sizes and allows to minimize their influence on porosity.

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Hoskins, David, und Genevieve Palardy. „High-speed consolidation and repair of carbon fiber/epoxy laminates through ultrasonic vibrations: A feasibility study“. Journal of Composite Materials 54, Nr. 20 (28.01.2020): 2707–21. http://dx.doi.org/10.1177/0021998320903097.

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Ultrasonic welding is a common fusion bonding technique to join unreinforced and reinforced thermoplastics. It is expected that applying ultrasonic vibrations to thermoset prepregs can produce heat generation to promote resin flow and consolidation. This paper discusses the feasibility of using ultrasonic vibrations as a high-speed repair technique for carbon fiber/epoxy prepregs to replace the traditional vacuum-bagging scarf setup. Three material types were investigated: out-of-autoclave unidirectional and plain weave prepregs (Cycom® 5320) and a general purpose twill weave prepreg (AS4/Newport 301). Two welding modes were considered: time and travel (vibrations stop once the desired vertical displacement is reached). For each mode, vibration time, travel, force, and amplitude were investigated. Cross-sectional analysis showed that void content equal to or below the vacuum-bagged samples could be achieved with ultrasonic consolidation to meet aerospace standards (≤2%). The following ultrasonic parameters were recommended to preserve prepreg tows integrity and minimize void content: vibration time below 1.0 s, travel between 12.5% and 50% of sample's initial thickness, force equal to or below 100 N, and amplitude below 41.3 μm. Temperature values recorded during the ultrasonic process reached the manufacturer's cure temperature range (120℃ to 180℃), with a predicted maximum degree of cure of 0.24. Interlaminar shear strength values were comparable for ultrasonically consolidated and vacuum-bagged samples. Soft and hard repair patches were applied to open-hole tensile coupons, with up to 50% strength recovery for both repair methods. Overall, ultrasonic consolidation has potential as a time- and cost-efficient repair method for thermoset prepregs.

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Proietti, Alice, Leandro Iorio, Nicola Gallo, Marco Regi, Denise Bellisario, Fabrizio Quadrini und Loredana Santo. „Recycling of Carbon Fiber Laminates by Thermo-mechanical Disassembly and Hybrid Panel Compression Molding“. Materiale Plastice 59, Nr. 1 (05.04.2022): 44–50. http://dx.doi.org/10.37358/mp.22.1.5558.

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An innovative recycling process for thermoset composite laminates is proposed by thermo-mechanical disassembly and further compression molding of hybrid thermoformable composite plates. Due to the thermo-mechanical process, single cured plies are extracted from the waste laminate. Subsequently re-lamination is performed by interposing thermoplastic films between the reclaimed composite plies. Final consolidation is carried out by compression molding. In order to show the feasibility of the novel recycling technology, carbon fiber reinforced composite plates by autoclave molding were thermo-mechanically disassembled in a manual roll bending machine after heating in oven. Reclaimed cured plies were laminated by alternating thermoplastic interlayers made of low density polyethylene. The hybrid laminate was consolidated at the temperature of 220�C and the holding pressure of 38.5 bar. Results from bending tests on virgin and recycled plates showed the very good agglomeration of the hybrid samples and the optimal preservation of performances of initial cured plies of the virgin material into the recycled plate.

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Yassin, Khaled, und Mehdi Hojjati. „Processing of thermoplastic matrix composites through automated fiber placement and tape laying methods“. Journal of Thermoplastic Composite Materials 31, Nr. 12 (26.11.2017): 1676–725. http://dx.doi.org/10.1177/0892705717738305.

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Fiber-reinforced composite materials are replacing metallic components due to their higher specific strength and stiffness. Automation and thermoplastics emerged to overcome the time and labor intensive manual techniques and the long curing cycles associated with processing thermoset-based composites. Thermoplastics are processed through fusion bonding which involves applying heat and pressure at the interface. Together with automated techniques (such as automated fiber placement, and automated tape laying), a fast, clean, out-of-autoclave, and automated process can be obtained. A detailed review of thermoplastic composites processing through automated methods is presented. It sheds the light on the materials used and the different heat sources incorporated with the pros and cons of each, with concentration mainly on hot gas torch, laser, and ultrasonic heating. A thorough illustration of the several mechanisms involved in a tow/tape placement process is tackled such as heat transfer, intimate contact development, molecular interdiffusion, void consolidation and growth, thermal degradation, crystallization, and so on. Few gaps and recommendations are included related to materials, laser heat source, heat transfer model, and the use of silicone rubber rollers. A review of optimization studies for tape placement processes is summarized including the main controllable variables and product quality parameters (or responses), with some of the major findings for laser and hot gas torch systems being presented. Both mechanical and physical characterizations are also reviewed including several testing techniques such as short beam shear, double cantilever beam, lap shear, wedge peel, differential scanning calorimetry, and so on. Challenges, however, still exist, such as achieving the autoclave-level mechanical properties and complying with the porosity levels required by the aerospace industry. More work is still necessary to overcome these challenges as well as increase the throughput of the process before it can be totally commercialized.

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Zucco, G., V. Oliveri, M. Rouhi, R. Telford, G. Clancy, C. McHale, R. O’Higgins, T. M. Young, P. M. Weaver und D. Peeters. „Static test of a variable stiffness thermoplastic composite wingbox under shear, bending and torsion“. Aeronautical Journal 124, Nr. 1275 (22.01.2020): 635–66. http://dx.doi.org/10.1017/aer.2019.161.

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AbstractAutomated manufacturing of thermoplastic composites has found increased interest in aerospace applications over the past three decades because of its great potential in low-cost, high rate, repeatable production of high performance composite structures. Experimental validation is a key element in the development of structures made using this emerging technology. In this work, a $750\times640\times240$ mm variable-stiffness unitised integrated-stiffener out-of-autoclave thermoplastic composite wingbox is tested for a combined shear-bending-torsion induced buckling load. The wingbox is manufactured by in-situ consolidation using a laser-assisted automated tape placement technique. It is made and tested as a demonstrator section located at 85% of the wing semi-span of a B-737/A320 sized aircraft. A bespoke in-house test rig and two aluminium dummy wingboxes are also designed and manufactured for testing the wingbox assembly which spans more than 3m. Prior to testing, the wingbox assembly and the test rig were analysed using a high fidelity finite element method to minimise the failure risk due to the applied load case. The experimental test results of the wingbox are also compared with the predictions made by a numerical study performed by nonlinear finite element analysis showing less than 5% difference in load-displacement behaviour and buckling load and full agreement in predicting the buckling mode shape.

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Vidrih, Tadej, Peter Winiger, Zafiris Triantafyllidis, Valentin Ott und Giovanni P. Terrasi. „Investigations on the Fatigue Behaviour of 3D-Printed Continuous Carbon Fibre-Reinforced Polymer Tension Straps“. Polymers 14, Nr. 20 (11.10.2022): 4258. http://dx.doi.org/10.3390/polym14204258.

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The focus of this research is an investigation on the fatigue behaviour of unidirectional 3D-printed continuous carbon fibre-reinforced polymer (CFRP) tension straps with a polyamide matrix (PA12). Conventionally produced tension straps are becoming established components in the mechanical as well as the civil engineering sector, e.g., as rigging systems for sailing boats and cranes and—recently introduced—as network arch bridge hangers. All these structures are subjected to high fatigue loads, and although it is commonly reported that carbon fibre-reinforced polymers show excellent fatigue resistance, there is limited understanding of the behaviour of CFRP loop elements under such loads, especially in combination with fretting at the attachment points. Research on this topic was performed at Empa in the past decade on thermoset CFRP straps, but never before with 3D-printed continuous CFRP straps with a thermoplastic matrix. This paper examines an additive manufacturing and post-consolidation method for producing the straps and presents initial results on their fatigue performance, which show that the fatigue endurance limit of the investigated 3D-printed and post-consolidated CFRP strap design is acceptable, when compared to steel tendons. However, it is still 20% lower than conventionally produced CFRP straps using out-of-autoclave unidirectional carbon fibre prepregs. The reasons for these findings and potential future improvements are discussed.

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Maes, Vincent K., Arjun Radhakrishnan, Jamie Hartley, Stuart Sykes und James Kratz. „Tracking consolidation of out-of-autoclave prepreg corners using pressure sensors“. Composites Part A: Applied Science and Manufacturing, August 2022, 107172. http://dx.doi.org/10.1016/j.compositesa.2022.107172.

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Iorio, Leandro, Fabrizio Quadrini, Nicola Gallo und Loredana Santo. „Out-of-autoclave molding of carbon fiber laminates by consolidation with shape memory polymer foams“. Journal of Composite Materials, 19.09.2023. http://dx.doi.org/10.1177/00219983231204117.

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Carbon fiber reinforced (CFR) laminates have been manufactured by an innovative out-of-autoclave (OOA) process thanks to the use of smart materials. In this study, for the first time, a shape memory polymer (SMP) foam has been used into a pressure dome to apply the consolidation pressure to the laminate. Heat for resin curing was supplied by a thermal blanket between the laminate and the SMP foam. In order to test the OOA molding process, 24-ply CFR laminates were manufactured and tested. For comparison and reference, CFR laminates were also molded by traditional vacuum bagging and autoclave curing. Samples for bending tests were extracted from OOA and autoclave molded plates. Results show that the SMP-OOA process is able to provide optimal laminate consolidation, despite of the low applied pressure (about 1 bar). A comparable density and ply thickness was measured on samples by the innovative and the conventional molding process, whereas a higher bending strength (+5%) was found on OOA samples. A higher dispersion was also observed for the properties of SMP-OOA molded laminates in comparison with autoclave, probably due to the prototyping nature of the molding technique in comparison with the well-known autoclave practice. Nevertheless, the final quality of the molded laminates is very high, and the SMP-OOA process is a very promising candidate as a technology to repair CFR structures.

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Saffar, Florence, Camille Sonnenfeld, Pierre Beauchêne und Chung Hae Park. „In-situ Monitoring of the Out-Of-Autoclave Consolidation of Carbon/Poly-Ether-Ketone-Ketone Prepreg Laminate“. Frontiers in Materials 7 (25.06.2020). http://dx.doi.org/10.3389/fmats.2020.00195.

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Iorio, Leandro, Denise Bellisario, Nicola Gallo, Claudia Papa, Marco Regi, Daniele Santoro, Fabrizio Quadrini und Loredana Santo. „Anisogrid lattice cylinders made of thermoplastic composite under buckling loading“. ESAFORM 2021, 10.04.2021. http://dx.doi.org/10.25518/esaform21.2798.

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Anisogrid lattice cylinders have been produced by means of an innovative out-of-autoclave (OOA) process by using thermoplastic prepreg. Unidirectional thermoplastic tapes with polypropylene matrix and glass fibers were wound on cylindrical mandrels at room temperature. Composite consolidation was achieved by using the compression of a heat-shrink tube during its shape recovery in oven. A cylindrical anisogrid lattice structure was manufactured and mechanically tested under vertical loading. Results from the buckling test revealed the optimal adhesion between prepreg layers after the out-of-autoclave molding. Numerical modelling of buckling has been performed to correlate the structural behavior of the anisogrid lattice cylinder with composite material properties and geometrical features. A parametric model of the lattice structure has been defined for this aim. The proposed manufacturing technology combines the advantages of thermoplastic composites (reparability, easy handling, easy storage, long prepreg life, productivity) with the designing potential of anisogrid lattice structures in terms of lightness and stiffness.

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Rizzolo, Robert, Daniel F. Walczyk und Daniel Montoney. „The Effect of Electron Beam Irradiation on Elastomers Used in Tooling for Composites Manufacturing“. Journal of Manufacturing Science and Engineering, 02.01.2021, 1–8. http://dx.doi.org/10.1115/1.4049493.

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Abstract This technical brief discusses material degradation issues and potential remedies related to advanced thermoset composites manufacturing using a new out-of-autoclave consolidation and curing process called ‘Electron Beam processing of Specialized Elastomeric Tooling combined with Resin Infusion’ (EB-SETRI). The design process for EB-SETRI tooling based on finite element structural analysis and Monte Carlo simulations of EB attenuation within tooling materials is briefly described. Of particular interest in this paper is the elastomeric mask, since it exhibits significant changes in mechanical properties based on prior work. Samples of five different silicone blends (four different durometers and two different catalysts) and one urethane (elastomeric mask materials of choice) were irradiated by an EB source with 3.0 MeV maximum power to simulate the conditions experienced by EB-SETRI tooling during processing. Changes in surface hardness and compression modulus were measured using ASTM D575 and D2240 as a function of dosage. Urethane embrittles and becomes unusable even at low doses, whereas silicone generally hardens to a maximum level at higher doses, presumably due to increased crosslinking density, and modulus increases linearly. The embrittlement of silicone is shown to be a result of the EB irradiation and not due to a temperature increase from energy absorption. Changes in elastomer mechanical properties confound process performance as a result, and several concepts for dealing with these changes are suggested. Although the experimental focus is on EB-SETRI, results are applicable to any manufacturing process that combines the use of EB irradiation and elastomers.

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Becerra, Luis Humberto Campos, Marco Antonio Loudovic Hernández Rodríguez, Raúl Lesso Arroyo, Hugo Esquivel Solís und Alejandro Torres Castro. „Effect of sterilization on 3-point dynamic response to in vitro bending of an Mg implant“. Biomaterials Research 25, Nr. 1 (06.04.2021). http://dx.doi.org/10.1186/s40824-021-00207-9.

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Abstract Background The aim of the study is to characterize a biomedical magnesium alloy and highlighting the loss of mechanical integrity due to the sterilization method. Ideally, when using these alloys is to delay the onset of degradation so that the implant can support body loads and avoid toxicological effects due to the release of metal ions into the body. Methods Standardized procedures according to ASTM F-1264 and ISO-10993-5 were used, respecting detailed methodological controls to ensure accuracy and reproducibility of the results, this testing methodology is carried out in accordance with the monographs of the Pharmacopoeia for the approval of medical devices and obtaining a health registration. An intramedullary implant (IIM) manufactured in magnesium (Mg) WE43 can support loads of the body in the initial period of bone consolidation without compromising the integrity of the fractured area. A system with these characteristics would improve morbidity and health costs by avoiding secondary surgical interventions. Results As a property, the fatigue resistance of Mg in aggressive environments such as the body environment undergoes progressive degradation, however, the autoclave sterilization method drastically affects fatigue resistance, as demonstrated in tests carried out under in vitro conditions. Coupled with this phenomenon, the relatively poor biocompatibility of Mg WE43 alloys has limited applications where they can be used due to low acceptance rates from agencies such as the FDA. However, Mg alloy with elements such as yttrium and rare earth elements (REEs) have been shown to delay biodegradation depending on the method of sterilization and the physiological solution used. With different sterilization techniques, it may be possible to keep toxicological effects to a minimum while still ensuring a balance between the integrity of fractured bone and implant degradation time. Therefore, the evaluation of fatigue resistance of WE43 specimens sterilized and tested in immersion conditions (enriched Hank’s solution) and according to ASTM F-1264, along with the morphological, crystallinity, and biocompatibility characterization of the WE43 alloy allows for a comprehensive evaluation of the mechanical and biological properties of WE43. Conclusions These results will support decision-making to generate a change in the current perspective of biomaterials utilized in medical devices (MDs), to be considered by manufacturers and health regulatory agencies. An implant manufactured in WE43 alloy can be used as an intramedullary implant, considering keeping elements such as yttrium-REEs below as specified in its designation and with the help of a coating that allows increasing the life of the implant in vivo.

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