•Maleic anhydride and acrylic copolymer were introduced to form an ion crosslinking.•Ion networks work in concert with other actions to limit molecular chain slide.•The reversible of the ion ...cross-linking network increases production efficiency.•The thermal stability and mechanical properties of PVC foam material are improved.•The dimensional stability of the PVC foam depends on maleic anhydride content.
This study details a novel approach to enhance the dimensional stability of foamed polyvinyl chloride (PVC) materials through the introduction of a reversible cross-linking network. This is achieved via the carboxylation of acrylate polymers (ACR) utilizing the hydrolysis reaction of maleic anhydride (MAH) during the extrusion of PVC foam sheets. Subsequently, an ionic cross-linking network is formed using calcium-zinc (Ca-Zn) stabilizers. This paper elucidates the process of cell formation and the mechanisms underpinning the ACR/MAH ion network formation. Cell morphology of the foamed PVC was characterized using SEM, and the effects of ionic cross-linking on the plasticizing time, dimensional stability, and mechanical properties were analyzed through cell diameter distribution measurements and rheometry. The longitudinal and transverse dimensional shrinkage of PVC-F/MAH1 was reduced by 28.0 % and 28.9 %, respectively. The construction of the ACR/MAH ion cross-linking network not only augments the mechanical properties but also substantially enhances the dimensional stability of the material. This approach underscores the viability of ion cross-linking networks in advancing the performance parameters of PVC foams, suggesting a promising avenue for future research and development in polymer processing technology, and potentially expanding their application spectrum.
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This work presents a detailed experimental study conducted for a range of different lay-ups using thin-ply carbon fiber reinforced polymer (CFRP) laminates. The selection of the laminates was ...performed relying on their level of anisotropy. The laminates vary from a quasi-isotropic (QI) laminate, which is weakly anisotropic, to a cross-ply (CP) laminate, which is strongly anisotropic. The laminates were tested in on-axis and off-axis open hole tension (OHT). The main objective was to observe the effect of the level of anisotropy of the laminate on the macroscopic failure and observed failure patterns. It is shown that, contrary to most existing observations so far, depending on the lay-up and consequently its level of anisotropy, open-hole, quasi-homogeneous thin-ply laminates do not necessarily exhibit a fiber dominated failure mode, but could develop sub-critical damage mechanisms in a large extent prior to ultimate failure, reminiscent of what is observed for standard-ply CFRP laminates.
Accurate determination of thermo‐mechanical properties in precipitation hardenable materials using an electro‐thermal mechanical testing (ETMT) system is a well‐established challenge. The non‐uniform ...distribution of temperature resulting from heating based on the joule effect (i.e., resistivity heating) leads to heterogeneous deformation along the gauge length, owing to the temperature dependency of mechanical properties, which makes their direct measurements complicated. This study presents an evaluation of four different miniaturised sample geometries that were tested to achieve an optimised sample with acceptable uniform strain and temperature distributions in the gauge volume. In‐situ displacement mapping, using digital image correlation (DIC), was utilised to calibrate the optimised sample dimensions with the aim of forcing the deformation to the hottest region of the gauge lengths during the tests. Tests were carried out on Inconel 718 (IN718) at 720°C, an optimal temperature for the precipitation of γ″, the primary strengthening particle in this alloy. The results showed that only in the case of the geometry proposed in this study (i.e., a sample with a short gauge length ~2 mm) did the deformation acceptably localise at the centre, compared to other geometries. A correction methodology is developed that equates the strain measured using DIC over the 2 mm gauge length of the modified sample geometry with the strain measured using the linear variable differential transformer (LVDT) integrated to the ETMT, making future tests on IN718, and other precipitation hardenable materials, possible without the need for the use of a DIC system.
The rapid rise in the applications of carbon fibre reinforced polymer matrix composites (CFRPs) is creating a waste recycling challenge. The use of high-performance thermoset polymers as the matrix ...makes the recovery of the fibres and the resins extremely difficult. Implementation of a circular economy that can eliminate waste and re-use resources warrants the use of efficient processes to recycle end-of-life CFRP components and manufacturing wastes. To this end, herein we present a critical review of the current technologies for recovering carbon fibres and/or the polymers and re-manufacturing CFRPs. New research opportunities in developing new biodegradable thermosets and thermoplastic matrices are also outlined together with more radical recycling strategies for the future.
In this paper a comprehensive experimental study on effects of different fibre waviness characteristics on the compressive properties of unidirectional non-crimp fabrics (NCF) composites is ...presented. The fibre waviness ranges from periodic to random with medium to large misalignment angles. As expected, fibre waviness is found to strongly impair the compressive mechanical properties of the composite. It is demonstrated that the maximum fibre misalignment alone can be used to accurately predict strength with analytical kinking criteria. Furthermore, there is a direct correlation between waviness and a knock-down factor on stiffness with approximately 5%/degree mean fibre misalignment angle. Analysis of the extension of the misaligned regions (defects) provides additional evidence that defect extension in the transverse direction is more critical than in the longitudinal direction, supporting earlier theoretical predictions in the open literature.
The fatigue/fracture behaviour of bi-material Aluminium/CFRP (Carbon-Fibre Reinforced Polymer) bonded joints was addressed in this work using the modified Paris law. Five types of tests were employed ...to cover appropriately the entire mode I – mode II range. Data reduction schemes based on equivalent crack length concept were developed for all types of tests. Following this methodology, the compliance versus number of cycles relation becomes sufficient to perform post-processing fatigue data analysis. The coefficients of the modified Paris law for each type of test were obtained by fitting a power law to the crack growth rate versus the ratio of total strain energy release rate and its critical value. The objective was to obtain relations representative of the evolution of those coefficients as function of mode ratio. These relations were subsequently input in a cohesive zone model at the local level, i.e., at each integration point. It was verified that the compliance versus number of cycles curves and the fatigue lives predicted numerically are in agreement with the experimental values.
•20 wt% PCM in the foam core provided heat storage (29 J/g) and kept insulation (<0.035 W/m.K));•Skin/core adhesion remained excellent also with PCM;•Sandwich panels had comparable flexural strengths ...and facing stresses to neat PU control;•Lightweight, energy-efficient composites for thermal management in aerospace and refrigerated transport.
This work aims at developing novel multifunctional sandwich composites with optimized thermal energy storage and structural load-bearing performance by incorporating microencapsulated phase change materials (PCMs) into polyurethane (PU) foam cores. The optimized foam containing 20 wt% PCM, balancing good latent heat storage (up to 29 J/g) with low thermal conductivity (up to 0.035 W/(m·K) at 50 °C), was used to produce sandwich panels with high-performance epoxy/carbon fiber laminate skins. Microstructural characterization confirmed excellent interfacial adhesion between the core and skins. The multifunctional panels exhibited comparable flexural strengths (150 kPa) and facing stresses (25 MPa) to neat PU sandwich controls. By integrating thermal regulation from PCM phase change with structural reinforcement from the sandwich architecture in a single multifunctional material system, this work contributes to the development of lightweight, energy-efficient composite materials suitable when weight reduction and thermal management are paramount, such as in aeronautics and cold chain logistics.
Continuous fiber-reinforced polymer (FRP) composites have been used for many applications to create strong yet lightweight products due to their high strength-to-weight and stiffness-to-weight ...ratios. Aerospace 1, automotive 2, and sport 3industries are three of the few industries that have been using FRP composites. The increasing need for prototyping and customization of fiber reinforced polymer composite parts is prompting innovations in new manufacturing processes to realize short manufacturing cycle time and low production cost, which is challenging to accomplish using conventional molding process. Fused filament fabrication (FFF) - a material extrusion additive manufacturing (AM) technique trademarked as fused deposition modelling (FDM) by Stratasys- holds promise to achieve low-cost production on continuous fiber-reinforced thermoplastic (FRTP) composites. In this paper, the FFF technique is employed to fabricate continuous carbon and glass FRTP composites and its microstructural characteristics and the resulting tensile, flexural, and quasi-static indentation characteristics of the printed composites are examined. Additionally, the fracture behavior of each test sample is evaluated and discussed in detail.
•A comparison of fracture behaviors between 3D-printed carbon and glass fiber reinforced composites is performed.•Difference in fracture behavior between glass and carbon fibers reinforced composites is observed in flexural test.•Similar fracture behavior is observed for tensile and quasi-static indentation tests.
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Using austenitic steel in welding structures requires both destructive and non-destructive testing (NDT) to approve the use of intended welding specification, but also testing of material properties, ...even if they are guaranteed by manufacturer. In this particular case, X2CrNiMo17-12-2 (commercial trademark AISI 316L) is the material that has to be partly replaced by NiCr21Mo (commercial trademark Incoloy 825) in a piece of process equipment exposed to elevated temperature and highly corrosive environment. This research presents an investigation of overmatching V groove welded joint made of these two austenitic steels. Due to materials properties and specific application conditions, low heat input TIG welding was utilized. Mechanical properties of welded joint have been examined to check criteria which guarantees safe work and integrity of welded components. Chemical composition of used filler material was close to the one of NiCr21Mo alloy, providing weld overmatching, which needs to be checked as well. Mechanical testing (tensile, bending, impact, hardness), macro-and microstructure analysis provided detailed insight into welded joint characteristics and a ground for further investigation concerning heterogeneous austenitic welded joint, taking into account overmatching effect.