Functional Composite Materials
EISSN : 2522-5774
Published by: Springer Science and Business Media LLC (10.1186)
Total articles ≅ 20
Latest articles in this journal
Functional Composite Materials, Volume 2, pp 1-14; doi:10.1186/s42252-021-00024-2
This paper focuses on the physicochemical changes that happen in cold mix asphalts during curing, and more specifically, while and after transitioning to different simulated seasons. Several tests were carried out in order to better grasp the influence of the weather (temperature and humidity) on the curing of such materials. The mechanical behaviour of the mix was assessed using oedometer tests. The physicochemical evolutions of extracted binders, such as oxidation and rheology, were evaluated. The results show stiffening of the mix and ageing of the binder linked to a higher temperature and a lower humidity. A low temperature and high moisture seem to slow down these evolutions. However the binder behaviour does not explain the whole mix behaviour as the kinetics between them are not always similar. Thus other mechanisms are yet to be found and taken into account to fully understand cold mix asphalts behaviour.
Functional Composite Materials, Volume 2, pp 1-13; doi:10.1186/s42252-021-00019-z
Traditional laminated composites have fibres oriented only in the in-plane of the laminate due to their manufacturing process, and are therefore very susceptible to transverse cracking and delamination from out-of-plane actions. Delamination can considerably reduce the load bearing capacity of a structure hence several reinforcement solutions, based on the principle to add out-of-plane reinforcement to the 2D fabric, have been explored to enhance the delamination resistance. However, the usual textile technologies for Z-reinforcement such as weaving, knitting, stitching, z-pinning, and tufting generates perturbations that may alter the in-plane mechanical properties. Although tufting is a single needle and single thread based one side stitching (OSS) technique which can incorporate almost tension free through the thickness reinforcement in a material, various types of microstructural defects may be created during the manufacturing process and lead to a degradation of the in-plane properties of the composite. Moreover, due to awareness in environmental concerns, the development and use of eco-friendly biocomposites to replace synthetic ones has been increasing. This research work investigates the effect on in plane mechanical properties of adding through the thickness reinforcement (TTR) by tufting in a flax based composite laminate to improve the transversal strength. The glass fibre tufted laminates of 550 g/m2 flax fibre were moulded using a 38% biobased thermoset resin by vacuum bag resin transfer moulding (VBRTM). The tufted and un-tufted in-plane mechanical properties of green biocomposite were determined in tension, compression and shear in accordance with ASTM 3039, ASTM D7137 and EN ISO 14130, using universal INSTRON 1186 and MTS 20 M testing machines. The quantification of the in-plane mechanical properties established a reduction of the in plane tensile mechanical properties, due to tufting, whereas the reduction effects are marginal in compression. As expected, the glass fibre tufts strength the connection between core and skin of the composite so that the interlaminar shear strength, deduced from flexural tests with small span-to-thickness ratio, is increased. Thanks to Digital Image Correlation (DIC) performed during shear tests, an increase in interlaminar shear modulus is highlighted.
Functional Composite Materials, Volume 2, pp 1-11; doi:10.1186/s42252-021-00022-4
Renewable and environmentally responsive materials are an energy- and resource-efficient approach in terms of civil engineering applications, e.g. as so-called smart building skins. To evaluate the influence of different environmental stimuli, like humidity or solar radiation, on the long-term actuation behavior and mechanical robustness of these materials, it is necessary to precisely characterize the magnitude and range of stimuli that trigger reactions and the resulting kinetics of a material, respectively, with suitable testing equipment and techniques. The overall aim is to correlate actuation potential and mechanical properties with process- or application-oriented parameters in terms of demand-oriented stimuli-responsive element production. In this study, the impact of solar radiation as environmental trigger on the cellulose-based humidity-sensing material Cottonid, which is a promising candidate for adaptive and autonomously moving elements, was investigated. For simulating solar radiation in the lab, specimens were exposed to short-wavelength blue light as well as a standardized artificial solar irradiation (CIE Solar ID65) in long-term aging experiments. Photodegradation behavior was analyzed by Fourier-transform infrared as well as electron paramagnetic resonance spectroscopy measurements to assess changes in Cottonid’s chemical composition. Subsequently, changes in micromechanical properties on the respective specimens’ surface were investigated with roughness measurements and ultra-micro-hardness tests to characterize variations in stiffness distribution in comparison to the initial condition. Also, thermal effects during long-term aging were considered and contrasted to pure radiative effects. In addition, to investigate the influence of process-related parameters on Cottonid’s humidity-driven deformation behavior, actuation tests were performed in an alternating climate chamber using a customized specimen holder, instrumented with digital image correlation (DIC). DIC was used for precise actuation strain measurements to comparatively evaluate different influences on the material’s sorption behavior. The infrared absorbance spectra of different aging states of irradiated Cottonid indicate oxidative stress on the surface compared to unaged samples. These findings differ under pure thermal loads. EPR spectra could corroborate these findings as radicals were detected, which were attributed to oxidation processes. Instrumented actuation experiments revealed the influence of processing-related parameters on the sorption behavior of the tested and structurally optimized Cottonid variant. Experimental data supports the definition of an optimal process window for stimuli-responsive element production. Based on these results, tailor-made functional materials shall be generated in the future where stimuli-responsiveness can be adjusted through the manufacturing process.
Functional Composite Materials, Volume 2, pp 1-15; doi:10.1186/s42252-021-00021-5
Fusion assembly is a highly promising technique for joining thermoplastic composite to thermoset composites, enabling the use of both the most affordable composite material and process for each substructure. However, some major challenges need to be addressed such as functionalizing the thermoset composite surface through co-curing with an appropriate thermoplastic interlayer or realizing a fast and robust welding process that meets all quality and mechanical requirements. In this paper, we investigated the potential of polyetheretherketone (PEEK) and its amorphous (PEEK A) and semicristalline (PEEK SC) states as interlayer materials, co-cured onto thermoset composites. A surface preparation involving the atmospheric plasma process demonstrated that both PEEK state materials can be used as interlayer with favorable adhesion properties. The influence of the plasma treatment on surface properties and morphology was also experimentally characterized.
Functional Composite Materials, Volume 2, pp 1-21; doi:10.1186/s42252-021-00020-6
Additive manufacturing techniques established a new paradigm in the manufacture of composite materials providing a simple solution to build complex, custom designed shapes. In the biomedical field, 3D printing enabled the production of scaffolds with patient-specific requirements, controlling product architecture and microstructure, and have been proposed to regenerate a variety of tissues such as bone, cartilage, or the nervous system. Polymers reinforced with graphene or graphene derivatives have demonstrated potential interest for applications that require electrical and mechanical properties as well as enhanced cell response, presenting increasing interest for applications in the biomedical field. The present review focuses on graphene-based polymer nanocomposites developed for additive manufacturing fabrication, provides an overview of the manufacturing techniques available to reach the different biomedical applications, and summarizes relevant results obtained with 3D printed graphene/polymer scaffolds and biosensors.
Functional Composite Materials, Volume 2, pp 1-10; doi:10.1186/s42252-021-00023-3
This study was carried out using bleached softwood Chemi-Thermo-Mechanical Pulp to evaluate the influence of Molded Pulp Products’ manufacturing process parameters on the finished products’ mechanical and hygroscopic properties. A Taguchi table was done to make 8 tests with specific process parameters such as moulds temperature, pulping time, drying time, and pressing time. The results of these tests were used to obtain an optimized manufacturing process with improved mechanical properties and a lower water uptake after sorption analysis and water immersion. The optimized process parameters allowed us to improve the Young’ Modulus after 30h immersion of 58% and a water uptake reduction of 78% with the first 8 tests done.
Functional Composite Materials, Volume 2, pp 1-9; doi:10.1186/s42252-021-00017-1
The performance of electric sensors is continuously improving due to the demands of modern vehicles and electronic devices. Magnetic sensors are used in a wide field of applications. However, handling and mounting the typical high-performance rare earth permanent magnets are challenging due to their brittleness. A constant magnetic flux is a key property of the magnetic setup in many devices. State-of-the-art adhesive bonding of magnets in devices can cause problems due to the low durability and viscous behaviour of adhesive polymers, as the magnet may change its position and hence, the magnetic flux distribution in the magnetic setup changes. Ultrasonic welding is a powerful technique to join hybrid material systems quickly and reliably, providing high joint strength, even for brittle materials such as glasses, ceramics and rare earth permanent magnets. The latter is being investigated in this work for the first time. The ultrasonic welding process was adapted to join 316L stainless steel, representing potential components of magnetic devices, to Ni/Cu/Ni-coated Nd2Fe14B. In addition to directly joined steel/magnet-hybrids, ductile aluminium and nickel interlayers were used in order to enhance the joint strength. Process parameters were developed and evaluated considering the resulting shear strength of the joints. The highest shear strength of 35 MPa was achieved for 316L/Nd2Fe14B and 316L/Al/Nd2Fe14B, which is more than twice the shear strength of adhesively bonded joints of up to 20 MPa, according to the literature. The functional performance of the hybrid material systems, evaluated by the magnetic flux density of the hybrid material systems was the highest for directly bonded joints, and those with a nickel interlayer, which did not show any losses in comparison to the single magnet in its initial state. Joints with an aluminium interlayer showed losses of 3% and adhesively bonded joints showed losses of 7% of the magnetic flux density. In summary, the results of this work indicate that ultrasonic welding is a suitable technique to improve the production process and performance of magnetic devices.
Functional Composite Materials, Volume 2, pp 1-12; doi:10.1186/s42252-021-00018-0
Conventional carbon fibre laminates are known to be moderately electrically conductive in-plane, but have a poor through-thickness conductivity. This poses a problem for functionality aspects that are of increasing importance to industry, such as sensing, current collection, inductive/resistive heating, electromagnetic interference (EMI) shielding, etc. This restriction is of course more pronounced for non-conductive composite reinforcements such as glass, organic or natural fibres. Among various solutions to boost through-thickness electrical conductivity, tufting with hybrid micro-braided metal-carbon fibre yarns is one of the most promising. As a well-characterised method of through thickness reinforcement, tufting is easily implementable in a manufacturing environment. The hybridisation of materials in the braid promotes the resilience and integrity of yarns, while integrating metal wires opens up a wide range of multifunctional applications. Many configurations can be produced by varying braid patterns and the constituting yarns/wires. A predictive design tool is therefore necessary to select the right material configuration for the desired functional and structural performance. This paper suggests a fast and robust method for generating finite-element models of the braids, validates the prediction of micro-architecture and electrical conductivity, and demonstrates successful manufacturing of composites enhanced with braided tufts.
Functional Composite Materials, Volume 2, pp 1-8; doi:10.1186/s42252-020-00014-w
The aim of this work is to characterize the moisture-dependent actuation behavior of bioinspired and additively manufactured hygromorphs based by following deductive and inductive design approaches. Fused Filament Fabrication (FFF) is employed to print bilayered structures consisting of swellable active layers and rigid passive layers. The active layer is composed of a polylactic acid (PLA) matrix filled with different hygroscopic cellulosic materials (native and modified) up to a filler content of 50 m%. Acrylonitrile Butadiene Styrene (ABS) is used for the passive layer. The FFF process allows the generation of desired differential swelling properties in the composites upon moisture absorption. The moisture dependent actuation strain of the printed bilayers was determined by video analyses. Some influencing geometrical factors which contribute to the actuation were deduced from x-ray diffraction (XRD) and micro computed tomography (μCT). The investigation of the mean cellulose microfibril orientation on the surface of the active layer suggested a preferential orientation with respect to printing direction. Furthermore, a gradient of cellulosic material within a single printed layer was observed, which indicates fiber sedimentation. Comparison with the thermomechanical model derived from Timoshenko (1925) shows that the computational prediction of the moisture dependent actuation is considerably accurate for most selected cellulosic materials and filler contents.
Functional Composite Materials, Volume 2, pp 1-11; doi:10.1186/s42252-021-00016-2
Tungsten disulfide (WS2) nanotubes (NTs) are examined here as a filler for polylactide (PLA) for their ability to accelerate PLA crystallization and for their promising biocompatibility in relevant to biomedical applications of PLA-WS2 nanocomposites. In this work, we have studied the structural and thermal properties of PLA-WS2 nanocomposite films varying the concentration of WS2 NTs from 0 (neat PLA) to 0.6 wt%. The films were uniaxially drawn at 90 °C and annealed at the same temperature for 3 and 10 min. Using wide angle x-ray scattering, Raman spectroscopy and differential scanning calorimetry, we probed the effects of WS2 NT addition on the structure of the PLA films at various stages of processing (unstretched, stretching, annealing). We found that 0.6 wt% of WS2 induces the same level of crystallinity in as stretched PLA-WS2 as annealing in neat PLA for 10 min. These data provide useful insights into the role of WS2 NTs on the structural evolution of PLA-WS2 composites under uniaxial deformation, and extend their applicability to situations where fine tuning of PLA crystallinity is desirable.