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The material parameters required to describe material behavior can change with the age of the components due to chemical and physical aging processes. The finite element method (FEM) is a tool for designing components for later use. The aim of this study is to correlate the change in the mechanical properties of silicone elastomers from standard tests over a longer period of time with the parameters of the Mooney–Rivlin model. To date, there are no publications on the development of the Mooney–Rivlin parameters of silicone elastomers over a storage period. For this purpose, the Shore A hardness, rebound elasticity, compression set and tensile properties were investigated over an aging period of approx. 200 days on two liquid silicone rubbers (LSRs) and one room-temperature-vulcanizing (RTV) silicone rubber. Depending on the silicone elastomer used, different trends in the characteristic values can be observed over the storage period. In general, increases in the Shore A hardness, rebound resilience and stress at a 100% strain with a decrease in the compression set can be determined. In addition to standard tensile tests, the material's multiaxial behavior under tension was probed, and it was found that the similarly stress at a 100% strain increased. Finite element simulations verified the standard tensile test and corresponding Mooney–Rivlin model parameters. These parameters from the uniaxial tensile were validated in the multiaxial behavior, and the model's accuracy in representing material properties and the influence of aging on the FEM simulation were affirmed. [ABSTRACT FROM AUTHOR]

For the application of poly(lactic acid) (PLA) and PLA/starch composites in technical components such as toys, it is essential to know their degradation behavior under relevant application conditions in a hydrothermal environment. For this purpose, composites made from PLA and native potato starch were produced using twin-screw extruders and then processed into test specimens, which were then subjected to various one-week ageing processes with varying temperatures (23, 50, 70, 90 °C) and humidity levels (10, 50, 75, 90%). This was followed by mechanical characterization (tensile test) and identification of degradation using Gel Permeation Chromatography (GPC), Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), and Nuclear Magnetic Resonance spectroscopy (NMR). With increasing temperature and humidity, there was a clear degradation of the PLA, which could be reduced or slowed down by adding 50 wt.% starch, due to increased crystallinity. Hydrolysis was identified as the main degradation mechanism for PLA and PLA/starch composites, especially above the glass transition temperature, with thermo-oxidative degradation also playing a subordinate role. Both hydrolytic degradation and thermo-oxidative degradation led to a reduction in mechanical properties such as tensile strength. [ABSTRACT FROM AUTHOR]

This article shows three different water‐based physical blowing agents for liquid silicone rubber (LSR) in terms of physical, mechanical, and morphological properties depending on the manufacturing parameters and amounts of blowing agents. The compositions consist of common LSRs added with pure water, water–silicone oil emulsion, and aqueous silicone. The foaming process is initiated in an injection molding process. By subvolumetrically filling the mold, it is possible to foam the LSR during the injection molding process. This publication aims to compare different, water‐based blowing agents for LSR in the injection molding process. The results show that for all foams porosities between 0.25 and 0.4 are possible. An analysis of the foam structure shows that the aqueous silicone produces a significantly more homogeneous structure than the other two blowing agents. In addition, the mechanical properties are analyzed. For this purpose, tensile tests are carried out and the Shore hardness is determined. The elasticity and mechanical properties decrease slightly. The specific tensile strength also shows a small decrease, although this may be due to either the gradient of the foam structure or chemical reactions between the blowing agents and the LSR. [ABSTRACT FROM AUTHOR]

In the plastics industry, CFD simulation has been used for many years to support mold design. However, using simulation as a substitute for experimentation remains a major challenge to this day. This is due to the unknown congruence between simulation and experiment. The present work focuses on a comparison between simulation (generated with the software Moldflow Insight Ultimate from Autodesk Inc., San Francisco, CA, USA) and experiment by using molds of different complexity, where, in contrast to a large number of previous investigations, both the characteristics of the parts and the time series of the process parameters were compared with each other. For this purpose, the high-resolution time series of the process parameters injection pressure, flow rate, and cavity pressure as well as the mass and the dimensions of the manufactured parts were acquired during the experiments and the results were compared with the computations obtained from the simulation. In addition, potential causes like the material data, mesh and solver parameter, and the machine-specific behavior were analyzed to assess which of these causes may be decisive for a deviation between simulation and experiment. [ABSTRACT FROM AUTHOR]

Wood Textile Composites (WTCs) represent a new and innovative class of materials in the field of natural fiber composites. Consisting of fabrics made from willow wood strips (Salix americana) and polypropylene (PP), this material appears to be particularly suitable for structural applications in lightweight construction. Since the threads of the fabric are significantly oversized compared to classic carbon or glass rovings, fundamental knowledge of the mechanical properties of the material is required. The aim of this study was to investigate whether WTCs exhibit classic behavior in terms of fiber composite theory and to classify them in relation to comparable composite materials. It was shown that WTCs meet all the necessary conditions for fiber-reinforced composites in tensile, bending, and compression tests and can be classified as natural-fiber-reinforced polypropylene composites. In addition, it was investigated whether delamination between the fiber and matrix can be simulated by using experimentally determined mechanical data as input. Using finite element analysis (FEA), it was shown that the shear stress components of a stress tensor in the area of the interface between the fiber and matrix are responsible for delamination in the composite material. It was also shown that the resistance to shear stress depends on the geometric conditions of the reinforcing fabric. [ABSTRACT FROM AUTHOR]

Within this research semi‐crystalline polylactide and composites with 50 wt.% native potato starch were compounded and injection molded. The material was mechanically characterized by tensile, three‐point bending, and Charpy impact tests. These tests were carried out in the freshly molded state and after 332 and 792 h of storage at accelerated temperature or humidity. The respective activation energy was calculated by applying the Flynn‐Wall‐Ozawa method. The focus of the study was to investigate the correlation between the activation energy and the related mechanical and thermal properties. The results showed that the addition of native potato starch as a filler prevents the decrease in activation energy over the course of the experiments. Thus, the PLA/starch composite is more resistant to the two aging conditions than the pure PLA. When considering the mechanical properties, the pure PLA showed a large deviation of results compared to the initial value in a range of +63.88% to −33.96% with regard to the respective aging conditions, whereas the PLA/starch composite properties nearly always remained at the initial values. Through the investigation of the mechanical and thermal properties, it was shown that the steady activation energies are consistent with the mechanical properties, as these have shown only a small deviation of the mechanical properties during the duration of experiments for the PLA/starch composite. [ABSTRACT FROM AUTHOR]

This study investigates the adhesion properties of polycarbonate (PC) and liquid silicone rubbers (LSR) through surface activation using ultraviolet C (UVC) radiation. While self-adhesive LSRs adhere easily to certain thermoplastic composites such as polybutylene terephthalate (PBT) and polyamides (PAs), bonding to PC typically requires surface treatment due to the lack of compatible functional groups. Previous methods like plasma or flame treatment have been effective, but the use of UVC radiation for surface activation remains unexplored. Through experiments, it was found that UVC surface activation, particularly with ozone-generating lamps, significantly enhances the peel strength between PC and self-adhesive LSRs. The study evaluates the impact of different irradiation times and lamp configurations on peel resistance, surface energy, and composite stability. Results show that UVC/ozone (wavelengths 254 nm and 185 nm) activation increases peel resistance, with distinct differences observed between LSR types. Additionally, the study examines the stability of UVC activation over time and under various storage conditions, highlighting its effectiveness for up to 36 months at room temperature. Furthermore, the relationship between surface energy and peel strength is analyzed, finding that UVC/ozone activation increases surface energy but does not consistently correlate with improved adhesion. The study concludes with a comparison of UVC/ozone activation to alternative surface treatment methods, emphasizing its advantages such as cost-effectiveness and stability while considering limitations regarding substrate compatibility and occupational safety aspects. Overall, UVC/ozone surface activation presents a promising approach for enhancing adhesion in PC–LSR composite systems and holds potential for applications across various industries. [ABSTRACT FROM AUTHOR]

In order to produce a completely bio‐based and cost‐effective filled polymer, PLA and native potato starch as a filler were compounded by twin screw extrusion. Subsequently injection molded test specimens were manufactured and subjected to artificial weathering as well as different storages (high temperature, high humidity, freeze, water) for 504 h with a view to long‐term resistance. Depending on the starch content a significant reduction of up to 100% in tensile strength can be seen, as the starch accelerates or inhibits the triggered aging effects. As a result of the influence of humidity and water as well as artificial weathering, stress cracks are formed in starch‐containing samples. Storage at an elevated temperature (70°C, 50% RH) leads to polymer degradation of the PLA. This degradation can be inhibited by the addition of starch. Freezing storage has no significant influence on the mechanical and structural properties of the PLA starch composites. [ABSTRACT FROM AUTHOR]

The performance of an injection molding machine (IMM) influences the process and the quality of the parts manufactured. Despite increasing data collection capabilities, their machine-specific behavior has not been extensively studied. To close corresponding research gaps, the machine-specific behavior of two hydraulic IMMs of different sizes and one electric IMM were compared with each other as part of the investigations. Both the start-up behavior from the cold state and the behavior of the machine at different operating points were considered. To complement this, the influence of various material properties on the machine-specific behavior was investigated by processing an unreinforced and glass-fiber-reinforced polyamide. The results obtained provide crucial insights into machine-specific behavior, which may, for instance, account for disparities between computer fluid dynamic (CFD) simulations and experimental results. Furthermore, it is expected that the description of the machine-specific behavior can contribute to transfer knowledge when applying transfer learning algorithms. Looking ahead to future research, it is advised to create what is referred to as a "machine fingerprint", and this proposal is accompanied by some preliminary recommendations for its development. [ABSTRACT FROM AUTHOR]