Functional Composite Materials最新文献

The selective distribution of filler within polymer blends presents a compelling advantage, notably manifesting as a reduced percolation threshold when compared to an individual polymer matrix with a random filler dispersion. In this context, a thermoplastic elastomeric (TPE) blend comprising ethylene propylene diene rubber (EPDM) and linear low-density polyethylene (LLDPE), denoted as EL, has been meticulously formulated. The incorporation of varying amounts of conductive carbon black (Vulcan XC 72; VCB) into this TPE matrix has been achieved through conventional melt blending, yielding a composite material with exceptional electromagnetic interference (EMI) shielding effectiveness of -27.80 dB at 50 phr (parts per hundred rubber). This success is credited to the creation of a linked structure resulting from a dual-step percolation process. The selective distribution of carbon black (CB) throughout the TPE mixture results in a decreased critical concentration for connectivity and enhanced electromagnetic interference (EMI) shielding performance. This advancement underscores the potential of EPDM-LLDPE-VCB (ELV) composites to safeguard against electromagnetic radiation. It paves the way for their utilization in various techno-commercial applications, where a balance of mechanical strength, thermal stability, and flexibility is crucial.

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This article comprehensively discusses the mechanical and tribological properties of epoxy matrix composites filled with 100μm graphite particulates, at loadings ranging from 0 to 1wt%. The investigation also focuses on the effects of the graphite filler on the wear surface of the specimens, utilizing an optical microscope for analysis. The results revealed a significant decrease in the tensile strength of the composite, with a reduction of more than 50% observed at 1wt% graphite loading. However, the flexural strength exhibited an initial sharp increase at 0.1wt% graphite loading, followed by a decline at higher graphite contents. Moreover, both impact and hardness values demonstrated improvement as the graphite content increased. The addition of graphite particles led to a reduction in the friction coefficient, attributed to the solid lubrication capabilities of graphite. Furthermore, the wear rate exhibited a sharp decrease with an increase in graphite content due to the formation of a lubrication layer at the contact surface, effectively reducing the break-off of the specimen.

Heat-based local ablation techniques are effective treatments for specific oligometastatic and localized cancers and are being studied for their potential to induce immunogenic cell death and augment systemic immune responses to immunotherapies. The diverse technologies associated with thermal therapy have an unmet need for method development to enable device-specific experimentation, optimization, calibration and refinement of the parameter space to optimize therapeutic intent while minimizing side effects or risk to the patient. Quality assurance, training, or comparing thermal dose among different modalities or techniques using animal models is time and resource intensive. Therefore, the application and use of tissue mimicking thermosensitive, thermochromic liquid crystal and thermochromic paint phantom models may reduce costs and hurdles associated with animal use. Further, their homogenous composition may enable more precise assessment of ablative techniques. This review utilized SciFinder, Web of Science, PubMed and EMBASE to systematically evaluate the literature describing the background and applications of thermochromic liquid crystal, thermochromic paint and tissue-mimicking thermochromic phantoms used to characterize the thermal effects of ablation devices with a focus on facilitating their use across the medical device development life cycle.

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Sheet Moulding Compound (SMC) based composites have a large potential in industrial contexts due to the possibility of achieving comparatively short manufacturing times. It is however necessary to be able to numerically predict both mechanical properties as well as manufacturability of parts.

In this paper a fully 3D, semi-empirical model based on fluid mechanics for the compression moulding of SMC is described and discussed, in which the fibres and the resin are modelled as a single, inseparable fluid with a viscosity that depends on volume fraction of fibres, shear strain rate and temperature. This model is applied to an advanced carbon-fibre SMC with a high fibre volume fraction (35%). Simulations are run on a model of a squeeze test rig, allowing comparison to experimental results from such a rig. The flow data generated by this model is then used as input for an Advani-Tucker type of model for the evolution of the fibre orientation during the pressing process. Numerical results are also obtained from the software 3DTimon. The resulting fibre orientation distributions are then compared to experimental results that are obtained from microscopy. The experimental measurement of the orientation tensors is performed using the Method of Ellipses. A new, automated, accurate and fast method for the ellipse fitting is developed using machine learning. For the studied case, comparison between the experimental results and numerical methods indicate that 3D Timon better captures the random orientation at the outer edges of the circular disc, while 3D CFD show larger agreement in terms of the out-of-plane component. One of the advantages of the new image technique is that less work is required to obtain microscope images with a quality good enough for the analysis.

Given the greater global awareness of environmental impacts of plastics and the need to develop alternative materials from renewable natural resources, there has been an increasing drive over recent years to develop biobased and biodegradable composites, especially those produced from agro-industrial waste and byproducts. This perspective provides a brief introduction to the field as well as discussing some of the critical aspects to be considered as we accelerate the development of these novel alternative materials for a range of applications.

Incorporating inorganic nanomaterials into a polymer matrix is one of the most effective ways to create thermoelectric performance for applications where physical flexibility is essential. In this study, flexible thermoelectric nanocomposite films were synthesized by incorporating inorganic copper iodide (CuI) nanosheets as the filler into poly (3,4-ethylene dioxythiophene): poly (styrene sulfonate) (PEDOT: PSS). The process involved the preparation of bulk CuI from precursors and, subsequently, the nanosheet synthesis by dissolving the bulk CuI in dimethyl sulfoxide (DMSO). The morphology of the nanosheets and the nanocomposite films was thoroughly examined, and the film’s thermoelectric performance was evaluated using a standard thermoelectric measurement system, ZEM-3. The morphological observation revealed a triangular nanosheet geometry for CuI, with an average lateral dimension of ~33 nm. The PEDOT/CuI nanocomposite films were prepared by mixing CuI nanosheets with PEDOT: PSS through ultrasonication and filtration on a PVDF membrane. The film with 6.9 vol% of CuI nanosheets exhibited an electrical conductivity and Seebeck coefficient of 852.07 S·cm^-1 and 14.95 µV·K^-1, respectively. This resulted in an enhanced power factor of 19.04 µW·m^-1·K^-2, much higher than the individual composite components. It demonstrated a trend of increasing power factor with the nanosheets up to 6.9 vol% due to improved electrical conductivity. The increase in electrical conductivity can be attributed to the screening effect induced by DMSO, which leads to a conformational change in the PEDOT chains. Furthermore, an optimal fraction of CuI nanosheets also contributes to this conformational change, further enhancing the electrical conductivity.

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Aluminium matrix composites (AMC) do combine a high lightweight potential with a wide range of specific mechanical or thermal properties, depending on their material composition or the content of reinforcement particles, respectively. Currently, the three main production technologies for manufacturing such AMC are powder metallurgy, semi-solid processes and casting. Here, the AMC´s reinforcement proportion that can be processed depends on the chosen manufacturing strategy and is therefore often limited to a maximum value of 30 vol. %, due to agglomeration and porosity problems. In this context, the main objective is to understand the fundamental mixing behaviour of powder mixtures for AMC green body production having reinforcement contents of up to 50 vol.% SiC_p. For this purpose, powder mixtures of monomodal AlSi7Mg0.6 and different SiC_p fractions were prepared with different mixing times and speeds to investigate the influence of these mixing parameters on the homogeneity of the particle distribution. Afterwards, the influence of powder size on the mixing process was investigated. The results showed that a slower mixing speed resulted in faster homogenisation as well as a larger particle size can be faster mixed. Furthermore, a regression model was developed using mixing time, speed and particle loading, to determine sufficient mixing parameters.

Graphene enhanced thermoplastic composites offer the possibility of conductive aerospace structures suitable for applications from electrostatic dissipation, to lightning strike protection and heat dissipation. Spray deposition of liquid phase exfoliated (LPE) aqueous graphene suspensions are highly scalable rapid manufacturing methods suitable to automated manufacturing processes. The effects of residual surfactant and water from LPE on thin films for interlaminar prepreg composite enhancement remain unknown. This work investigates the effect of heat treatment on graphene thin films spray deposited onto carbon fibre/polyether ether ketone (CF/PEEK) composites for reduced void content. Graphene thin films deposited onto CF/PEEK prepreg tapes had an RMS roughness of 1.99 μm and an average contact angle of 11°. After heat treatment the roughness increased to 2.52 μm with an average contact angle of 82°. The SEM images, contact angle, and surface roughness measurements correlated suggesting successful removal of excess surfactant and moisture with heat treatment. Raman spectroscopy was used to characterise the chemical quality of the consolidated graphene interlayer. Spectral data concluded the graphene was 3–4 layered with predominantly edge defects suggesting high quality graphene suitable for electrical enhancement. Conductive-AFM measurements observed an increase in conductive network density in the interlaminar region after the removal of surfactant from the thin film. Heat treatment of the Control sample successfully reduced void content from 4.2 vol% to 0.4 vol%, resulting in a 149% increase in compressive shear strength. Comparatively, heat treatment of graphene enhanced samples (~ 1 wt%) reduced void content from 5.1 vol% to 2.8 vol%. Although a 25% reduction in shear strength was measured, the improved electrical conductivity of the interlaminar region extends the potential applications of fibre reinforced thermoplastic composites. The heat treatment process proves effective in reducing surfactant and thus void content while improving electrical conductivity of the interlayer in a scalable manner. Further investigations into graphene loading effects on conductive enhancement, and void formation is needed.

Epoxy is widely used material, but epoxy has limitations in terms of brittleness in failure, and thus researchers explore toughening and strengthening options such as adding a second phase or using electromagnetic fields to tailor toughness and strength, on demand and nearly instantaneously. Such approach falls into the category of active toughening but has not been extensively investigated. In this research, Si-BaTiO₃ nanoparticles were used to modify the electro-mechanical properties of a high-performance aerospace-grade epoxy so as to study its response to electric fields, specifically low field strengths. To promote uniform dispersion and distribution, the Si-BaTiO₃ nanoparticles were functionalised with silane coupling agents and mixed in the epoxy Araldite LY1564 at different content loads (1, 5, 10 wt%), which was then associated with its curing agent Aradur 3487. Real-time measurements were conducted using Raman spectroscopy while applying electric fields to the nanocomposite specimens. The Raman data showed a consistent trend of increasing intensity and peak broadening under the increasing electric field strength and Si-BaTiO₃ contents. This was attributed to the BaTiO₃ particles’ dipolar displacement in the high-content nanocomposites (i.e., 5 wt% and 10 wt%). The study offers valuable insights on how electric field stimulation can actively enhance the mechanical properties in epoxy composites, specifically in relatively low fields and thin, high-aspect-ratio composite layers which would require in-situ mechanical testing equipped with electric field application, an ongoing investigation of the current research.