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This article investigates and compares the effects of hydrothermal aging on carbon fibre / Elium™ thermoplastic composite and on carbon fibre / vinylester thermoset composite for marine application. Accelerated aging tests are performed by immersion in deionised water at 70 °C. Water diffusion, monitored by regular weighing, shows that both composites as well as Elium™ resin exhibit non-Fickian behaviour. Analytical models are proposed to fit the experimental curves and to identify and compare diffusion parameters. The aging effects on the microstructure are evaluated using SEM, while irreversibility of degradation mechanisms is investigated by desiccation tests. Mechanical tensile tests, performed before and after aging, show the slight impact of water on tensile modulus and tensile strengths for both materials. Furthermore, it was found that shear modulus and interlaminar shear strength undergo significant alteration related to irreversible physicochemical degradation of the matrix. Studied materials have shown different diffusion behaviours, but similar mechanical properties evolutions.

To develop durable composite materials, it is crucial to elucidate the correlation between nanoscale damage in thermosetting resins and the degradation of their mechanical properties. This study aims to investigate this correlation by performing cyclic loading tests on the cross-linked structure of diglycidyl ether bisphenol A (DGEBA) and 4,4′-diaminodiphenyl sulfone (44-DDS) using all-atom molecular dynamics (MD) simulations. To accurately represent the nanoscale damage in MD simulations, a bond dissociation algorithm based on interatomic distance criteria is applied, and three characteristics are used to quantify the microscopic damage: stress–strain curves, entropy generation, and the formation of voids. As a result, the number of covalent bond dissociations increases with both the cyclic loading and its amplitude, resulting in higher entropy generation and void formation, causing the material to exhibit inelastic behavior. Furthermore, our findings indicate the occurrence of a microscopic degradation process in the cross-linked polymer: Initially, covalent bonds align with the direction of the applied load. Subsequently, tensioned covalent bonds sequentially break, resulting in significant void formation. Consequently, the stress–strain curves exhibit nonlinear and inelastic behavior. Although our MD simulations employ straightforward criteria for covalent bond dissociation, they unveil a distinct correlation between the number of bond dissociations and microscale damage. Enhancing the algorithm holds promise for yielding more precise predictions of material degradation processes.

In the current system, the disposal of plastic materials causes serious environmental pollution such as the generation of carbon dioxide and destruction of the ecosystem by micro-plastics. To solve this problem, bioplastics, biomass and biodegradable plastics have been developed. As part of our research, we have developed novel bioplastics called “cell-plastics”, in which a unicellular green algal cell serves as a fundamental resource. The production of the cell-plastics would be expected to reduce environmental impact due to the usage of a natural product. Herein, to overcome the mechanical strength of cell-plastics, we used thermosetting epoxy and urethane resins containing Chlorella sp. as the green algae. We successfully fabricated thermosetting resins with a Chlorella sp. content of approximately 70 wt% or more. IR measurements revealed that the chemical structure of an epoxide or isocyanate monomer mixed with Chlorella sp. was modified, which suggests that the resins were hardened by the chemical reaction. In addition, we investigated the effect of thermosetting conditions such as temperature and compression for curing both resins. It was revealed that the Young’s moduli and tensile strengths were controlled by thermosetting temperature and compression, whereas the elongation ratios of the resins were constant at low values regardless of the conditions.

A novel algorithm for covalent bond dissociation is developed to accurately predict fracture behavior of thermosetting polymers via molecular dynamics simulation. This algorithm is based on the Monte Carlo method that considers the difference in local strain and bond-dissociation energies to reproduce a thermally activated process in a covalent bond dissociation. This study demonstrates the effectiveness of this algorithm in predicting the stress–strain relationship of fully crosslinked thermosetting polymers under uniaxial tensile conditions. Our results indicate that the bond-dissociation energy plays an important role in reproducing the brittle fracture behavior of a thermosetting polymer by affecting the number of covalent bonds that are dissociated simultaneously.

Compression resin transfer moulding (CRTM) has been widely used to manufacture automotive parts with reduced production cycle times. With the development of fast curing thermosetting resins, the CRTM process is a viable option for the high production rates in the transportation industry. However, the dynamic resin curing behaviour poses a potential risk of manufacturing defects in the part. In order to reduce the risk during the development of the tool and the process parameters, this paper proposes a modelling framework for the CRTM process when using fast curing resin systems. The work specifically focused on the coupling between heat transfer, resin cure, resin flow and preform compaction using a commercial code, PAM-RTM. The tool captures accurately the preform filling, temperature and resin pressure evolution during the injection and compression phase. The application of the framework was demonstrated for a complex 3D demonstrator. The predicted preform filling had an accuracy of 73% for the flow front evolution compared to the experimental results. This work demonstrates the validity of the framework proposed when dealing with resin systems that are challenging to process.

A C 60 -PEI-rGO hybrid was prepared by incorporating the fullerene (C 60 ) on the surface of PEI-modified reduced graphene oxide (rGO) and then used to modify the epoxy (EP) resin. Subsequently, the structure of GO and C 60 -PEI-rGO hybrid were well characterized, showing that the C 60 was homogenously anchored on the surface of PEI-rGO. The flame retardancy, mechanical properties, and thermal stability of as-prepared C 60 -PEI-rGO/EP nanocomposites were systematically investigated. Results show that the C 60 -PEI-rGO hybrid exhibits high flame retarding efficiency for EP. Specifically, the time to ignition of epoxy increases from 68 to 89 s with the addition of 1.0 wt% C 60 -PEI-rGO, which are unusual in polymer nanocomposites. In the meantime, the peaks of the heat release rate and total heat release of the modified epoxy reduce by 40.0% and 15.6%, respectively. The synergistic flame retardant mechanism of C 60 -PEI-rGO to EP is attributed to its unique structure combining both the high efficiency in capturing free radicals by C 60 , the barrier effect of layered of rGO and increase of crosslinking density of epoxy. It is shown that the thermal stability and mechanical properties of epoxy are simultaneously improved with the addition of C 60 -PEI-rGO. This work may pioneer a new and efficient method to fabricate fire retardant thermosetting resins with simultaneously other improved properties.

This work developed an electrically conductive thermosetting resin composite that transitioned from a liquid to solid without using solvents in response to an increase in temperature. This material has applications as a matrix for carbon fiber reinforced plastics. The composite comprised polyaniline (PANI) together with dodecyl benzene sulfonic acid (DBSA) as a liquid dopant in addition to a radical polymerization system made of triethylene glycol dimethacrylate with a peroxide initiator. In this system, micron-sized non-conductive PANI particles combined with DBSA were dispersed in the form of conductive nano-sized particles or on the molecular level after doping induced by a temperature increase. The thermal doping temperature was successfully lowered by decreasing the PANI particle size via bead milling. Selection of an appropriate peroxide initiator also allowed the radical polymerization temperature to be adjusted such that doping occurred prior to solidification. Optimization of the thermal doping temperature and the increased radical polymerization temperature provided the material with a high electrical conductivity of 1.45 S/cm.

Constructing models of thermophysical characteristics of polymer composite materials in the curing process is a highly pressing task that is substantiated in this paper. A mathematical model of hot curing of polymer composites based on a thermosetting resin in a mold is presented. Based on experimental temperature dependences of thermophysical characteristics measured under different conditions, modeling dependences of the volume heat capacity and thermal conductivity of fiber, fabric and granular polymer composites on the degree of cure and resin fraction during curing are obtained, with their distinctive feature being the replacement of the properties of a porous reinforcing filler with those of the cured resin in the model. The results of experiments and calculations are presented. The proposed models of thermophysical characteristics increase the accuracy of process modeling and calculation of optimal temperature-time curing cycles.

The paper gives a set of basic relations characterizing the phenomena of viscous polymer resin flow through fiber reinforcement and the resin curing process. We describe the technological process of manufacturing composite structures. The influence of the resin curing process on values of residual stresses in composite constructions is analyzed taking into account two components: thermal shrinkage and chemical shrinkage of resins. For cases of 2-D structures, the method of formulating such tasks has been demonstrated. The types of design variables appearing in the optimization problems in this area are also presented. The 2-D optimization problems have been formulated. Various optimization problems are solved in order to demonstrate the influence of discussed relations on values of residual stresses and curing processes of thermosetting resins.

Limonene dioxide (LDO) has the potential to find a wide application as a bio-based epoxy resin. Its polymerizations by catalyzed ring-opening, and by polyaddition with diamines were compared with the polymerizations of the commercial epoxy resins bisphenol-A diglycidyl ether (BADGE), and 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexane carboxylate (ECC). Differential scanning calorimetry (DSC) studies showed that LDO polymerizations suffer in all cases studied from incomplete conversions. Nuclear magnetic resonance (NMR) studies revealed that in cis-isomers of LDO the internal epoxide rings were not reacting. The low reactivity of this epoxide group was explained by mechanistic considerations making use of the Fürst-Plattner rule, or trans-diaxial effect. Due to diastereomeric diversity approximately one-fourth of epoxide groups present in LDO could not react. Therefore, a diastereoselective epoxidation of limonene could provide a fully reactive bio-based epoxy resin.