1,721,039 research outputs found
Reducing rubber-plastic friction in syringes through microstructured surface design and manufacturing
Full text linkPlastic syringes often rely on silicone oil lubrication to reduce plunger-barrel friction, leading to potential issues like oil droplet release and drug aggregation. This study explored an alternative approach combining two-photon polymerization, laser machining, and microinjection molding to manufacture micro-dimpled structures for low friction. Plastic microdimples with high area density and low aspect ratio significantly reduced the coefficient of friction against rubber, while the dimple profile proved crucial in facilitating replication and demolding. The results of this study provide valuable insights into reducing friction between rubber and plastic, particularly in applications like syringes. (c) 2024 The Author(s). Published by Elsevier Ltd on behalf of CIRP. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/
Analysis of the welding strength in hybrid polypropylene composites as a function of the forming and overmolding parameters
No full textThis work investigates the influence of the process parameters on the welding strength in hybrid polypropylene composites manufactured by injection overmolding. A hybrid T-joint specimen was designed to evaluate the global performance of the welding by means of tensile tests. The effects of the process parameters were evaluated in accordance the design of experiments approach and the maximum strength (UTS) was assumed as response variable. The effects of melt temperature and holding pressure, combined to a variothermal mold-control system, were investigated. The residual stresses induced by the process were considered by means of coupled thermo-fluid dynamic/structural finite-element analysis. Moreover, the topography of the laminate-side surface was characterized and the process-induced surface modification was related to the performance of the welding. Results show that the melt temperature contributes to increase the welding strength; conversely, the mold temperature counteracts this effect by increasing the residual stress at the interface. POLYM. ENG. SCI., 58:592–600, 2018. © 2017 Society of Plastics Engineers
Modeling the adhesion bonding strength in injection overmolding of polypropylene parts
Full text linkIn this work, the bonding strength of overmolded polypropylene is investigated and modeled. A T-joint specimen was designed to replicate the bonding between a base and an overmolded stem made of the same polymer: a previously molded plaque was used for the base, and the stem was directly overmolded. The effect of melt temperature, holding pressure, and localized heating was investigated following the design of experiments approach. Both the melt and base temperature positively affect the welding strength. On the contrary, the holding pressure negatively contributed, as the crystallization temperature significantly increases with pressure. Then, the bonding strength of the specimens was predicted using a non-isothermal healing model. Moreover, the quadratic distance of diffusion (based on the self-diffusion model) was calculated and correlated with the bonding strength prediction. The non-isothermal healing model well predicts the bonding strength when the reptation time is calculated within the first 0.09 s of the interface temperature evolution. The prediction error ranges from 1% to 35% for the specimens overmolded at high and low melt and base temperatures, respectively
Cohesive Zone Modeling of the Interface Fracture in Full-Thermoplastic Hybrid Composites for Lightweight Application
Full text linkWith the increasing demand for lightweight and high-performance materials in the automotive and aerospace industries, full-thermoplastic hybrid composites have emerged as a pivotal solution, offering enhanced mechanical properties and design flexibility. This work aims to numerically model the fracture strength in full-thermoplastic hybrid composites made by forming and overmolding organosheets. The mode I fracture was investigated by modeling the behavior of T-joint specimens under a tensile test following the cohesive zone modeling (CZM) approach. The sample was designed to replicate the connection between the laminate and the overmolded part. Double cantilever beam (DCB) specimens were manufactured with organosheets and tested to mode I opening to determine the interlaminar fracture toughness. The fracture toughness out of the mode I test with DCB specimens was used to define the CZM parameters that describe the traction-separation law. Later, due to the particular geometry of the T-join specimens that under tensile load work close to pure mode I, the cohesive parameters were determined by inverse analysis, i.e., calibrating the theoretical models to match experimental results. The fracture resistance T-joint specimens appeared dependent on the fiber-bridging phenomenon during the delamination. In particular, the presence of fiber-bridging visible from the experimental results has been replicated by virtual analyses, and it is observed that it leads to a higher energy value before the interface’s complete breakage. Moreover, a correspondence between the mode I fracture toughness of the DCB specimen and T-joint specimens was observed
Investigation of the inflow effect on weld lines morphology and strength in injection molding of short glass fiber reinforced polypropylene
No full textIn parts manufactured by injection molding, the regions affected by the presence of a weld line show worse mechanical properties, especially in the case of fiber-reinforced thermoplastics. This is mainly due to the unfavorable reinforcement orientation in the proximity of the weld line. The position and shape of a weld line, which develops where two different flows converge during the mold filling phase, can be modified by generating a pressure unbalance between flow fronts during the packing phase. This phenomenon is also known as “inflow” in the literature. In this work, the inflow phenomenon was obtained using side features located near the weld line. Its effect on weld line morphology and fibers orientation was investigated. The experimental results show that the inflow can modify the weld line position and shape. Furthermore, it can reorient the fibers in the weld line region, increasing the load at break and stiffness of the weld line by 19% and 15%, respectively. These effects were numerically modeled with a maximum error of 4%
Tribological effects of mold surface coatings during ejection in micro injection molding
No full textModeling of the ultrasound-assisted ejection in micro injection molding
No full textIn this paper, an ultrasound-aided ejection system was designed and tested for various polymers and mold topographies. The use of ultrasound vibration aims at decreasing the ejection friction by reducing its adhesion component, which is controlled by the real contact area developed in the filling phase of the injection molding process. The experiments indicate that the ultrasound vibration reduces the ejection friction up to a maximum of 16%. The effect depends on the polymer used and it increases for rougher mold surface. Moreover, the dependence of ejection friction on mold surface roughness, melt viscosity and elastic modulus at ejection was modeled using the experimental data
Bioactive and antibacterial glass particles as fillers in composite bone cements: Influence of amount and size on radio-opacity, bioactivity, mechanical and antibacterial properties
No full textIn this work, a bioactive and antibacterial glass has been added to a commercial PMMA-based bone cement to promote osteointegration and simultaneously limit bacterial contamination. The influence of the amount and size of glass powders on mechanical properties, radio-opacity, bioactivity and antibacterial effect of the composite cements has been estimated. The obtained results suggested that both filler's amount and size can affect the bending strength of the samples. The composites radio-opacity can be modulated by varying the amounts of glass and radio-opaque agent usually present in the commercial composition. The bioactive and antibacterial properties evaluation evidenced that introducing 10 wt.% of glass conferred a bioactive behaviour to the PMMA-based matrix and limited the bacterial contamination. Finally, an approach to technological transfer with controlled process parameters has been proposed
Using analytical and data-driven methods to develop a soft-sensor for flow rate monitoring in tube extrusion
Full text linkIn manufacturing polyvinyl chloride (PVC) tubes, the required thickness and weight depend on the extruder flow rate. The extruder setup can be very time-consuming and inefficient since it requires adjusting the screw rotational speed by trial & error, as the relation between the flow rate and the rotational speed is not known a priori. Furthermore, it is also affected by the material properties, the melt temperature, and the pressure drop in the die. Direct measuring the flow rate or the tube thickness would require expensive gravimetric dosers or X-ray systems, respectively. Therefore, a soft-sensor was developed to monitor tube thickness and its weight per unit length. Two alternative approaches are proposed to predict the extruder flow rate under wall slip conditions: one is based on a developed analytical model and one on data-driven algorithms. Results show that machine learning regression models can achieve high predictive performance (a relative error of 1.2% using a Support Vector Regressor)
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