Thermoset Polymer Matrix Research Articles

Advancements in Biofiller-Reinforced PLA Composites for 3D Printing: A Review

Additive manufacturing is key in realizing highly complex and high-performance composite materials. Among all the various kinds of functionality that could be added to a composite component, continuous fiber-reinforced composites have been drawing much attention because of their attractive combination of properties. The comprehensive spectrum of knowledge that ranges from the basics concerned with structure, morphology, synthesis, physical, and chemical properties finally reaches to this analytical study of advanced composites. Most generally, such a composite is structured on a thermoplastic or thermoset polymer matrix that embeds the load-carrying reinforcing fibers; probably best known are carbon, glass, and aramid fibers. These composites, which involve fibers continuously reinforcing, have high strength relative to their weight. They are also anisotropic, meaning they have qualities that vary from one direction to another – something which might be customisable for specific load cases. They warp and shrink less during their life in an outside environment than conventionally made bioplastics due to a fact that short fibers can provide reinforcement to them. This 3-D printing object is manufactured by special additive manufacture technology during the manufacturing process after compounding and extruding the fiber-reinforced composite filament. The final properties of 3D printed parts could be tailorable through changing variables such a fiber type, fiber length, volume fraction, polymer matrix material, orientation of fibers, and printing process parameters. These continuous fiber-reinforced 3D printed composites could achieve tensile strengths up to one GPa, have stiffness values reaching even a rating of countless Gpa, and have ad thicknesses in the range from about 1.4–1.8 g/cm³. This finding could be applied in basically all major industries, from aerospace and the automotive industry to sports gear. Such conclusions from the analysis may be useful in the selection of appropriate materials and techniques while even guiding the development of new applications with respect to such advanced composite materials.

Fabrication and mechanical performance investigation of jute/glass fiber hybridized polymer composites: Effect of stacking sequences

The green, biodegradable, and cost-effective properties of natural fiber-reinforced polymer composite materials have attracted significant interest when compared to synthetic polymer composites. Jute is a naturally occurring bast fiber that is inexpensive, durable, and often utilized. In contrast, glass is a composite material that is frequently used in various applications, despite its high cost and potential environmental risks. Owing to jute's superior mechanical properties, there is a great deal of potential for combining it with glass, which would lower the amount of glass used and the composite's overall cost. This study employed bleached jute fabric and non-woven glass fabric to develop neat jute, neat glass, and hybrid composites by using different stacking sequences. The composites were fabricated utilizing a thermoset polymer matrix by following the hand layup process. Subsequently, an investigation was carried out to examine the mechanical, physical, thermal, and morphological properties of these composites. Out of the developed samples, the neat jute presents the least tensile and bending strength at 31.35 MPa and 41.138 MPa respectively, whereas the neat glass composite demonstrates exceptional tensile and bending strengths at 132.03 MPa and 184.86 MPa respectively. In the case of hybrid samples, they exhibited mechanical capabilities that fell between neat jute and neat glass, which was attributed to the combination of glass with jute fabric and the placement of glass as the outer layer. Apart from that, we observed that the moisture take-up% and thermal conductivity of hybrids composite were within 4–4.3% and 0.28–0.32 Wm−1 K-1 respectively. Moreover, thermogravimetric analysis and morphological behavior were also assessed. However, this study suggested that jute and nonwoven glass fabric with different stacking sequences may be combined to create a reinforced hybrid composite that may have potential use in furniture, interior design, and inner sections of cars.

New metal-epoxy-matrix carbon-fibre hybrids to tackle stress concentration

The paper explores the feasibility of improving the performance of composite structures with stress concentrators by local infusion of metals. The resulting material architecture presents Multi-Matrix Continuously-Reinforced Composites (MMCRC) – with shared domains of both the thermoset polymer and metal matrices with fibre-bridged interfaces between the domains. The study explores the manufacturing routes to creating such composites and assesses the resulting performance using the open-hole tensile test. It has been demonstrated that the presence of a rigid multi-matrix patch around the open hole, exhibiting minimal thickness variation, leads to a 15.0% improvement in failure load and a 16.6% improvement in failure strain for quasi-isotropic carbon fibre composite laminates. The strain history analysis of the MMCRC samples indicates the occurrence of plastic yielding within the metal matrix and strain redistribution mechanisms, leading to load sharing over the hybrid matrix area.

EFFECT OF VARIOUS CHEMICAL TREATMENTS ON PHYSICOCHEMICAL AND THERMAL PROPERTIES OF ERYTHRINA VARIEGATA FIBERS: APPLICATION IN EPOXY COMPOSITES

Recently, there has been an increasing trend in utilizing lignocellulosic fiber reinforced composites in structural applications within the construction and automobile industries, replacing conventional materials based on metals and their derivatives. In the present study, Erythrina variegata fibers (EVFs) were subjected to a number of chemical treatments individually (alkalization, benzoyl peroxide, potassium permanganate, and stearic acid treatments). The effects of these chemical treatments on the EVFs were examined through chemical composition analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). This comprehensive analysis aimed to assess the suitability of the chemically treated EVFs for use as reinforcement in thermoset polymer matrix composites. The alkali treated fibers (AEVFs) were found as optimum and were then used as reinforcement in epoxy adhesives. Different fiber loadings (0, 5, 10, 15, 20, and 25 wt%) were incorporated into the epoxy matrix to investigate their effects on the properties of the composites. Therefore, the tensile strength, flexural strength, impact strength, and thermal stability of the prepared composites were evaluated under controlled laboratory conditions. The findings collectively suggested that the epoxy composites reinforced with 20 wt% of AEVFs exhibited promising characteristics for lightweight structural applications.

Thermoplastic and thermoset polymer matrix composites reinforced with bismuth oxide as radiation shielding materials

Polymer composites reinforced with heavy metals have wide applications in the nuclear industry as radiation shielding materials against emitted radiation from nuclear equipment. In this study, considering bismuth oxide as reinforcement, various polymers including thermoplastic polymers, such as high-density polyethylene, low-density polyethylene, polypropylene, polyvinyl acetate, polymethyl methacrylate, and thermosetting epoxy resin have been considered as matrices. After preparing various samples of polymer composites loaded with 60 % by weight of bismuth oxide, some physical, mechanical, and radiation shielding properties (neutron and gamma attenuation coefficients) of these polymer composites have been measured and compared with each other. First, the density of the samples was measured, and the response of these samples to varying compressive force was investigated. The stress-strain diagrams of composites with different matrices were compared. Subsequently, the linear and mass attenuation coefficients of the composites were measured over a wide range of energies (32–1480 keV) against direct and collimated beams from various standard gamma-ray sources (134Cs, 60Co, 154Eu, 133Ba, and 22Na) using an HPGe detector. A collimated beam from an Am–Be source was utilized to measure and compare the attenuation properties of the composite samples against neutron flux. Furthermore, the properties of the composites against neutron and gamma radiation were calculated using the MCNP Monte Carlo code over a broad energy range, and the results were compared and validated with the experimental data. The comparison of the calculated and measured results shows reasonable agreement. The results indicate that in situations where high attenuation properties coupled with high strength are desired, polymeric composites with an epoxy matrix can be considered as radiation shielding materials. If the use of flexible and malleable material is required, such as for reactor piping shielding or the fabrication of protective gloves and clothing in a radiation environment, among the polymers studied, polyvinyl acetate is a more suitable matrix.

Fabrication and Physico-mechanical Characterization of Short Natural/Synthetic Fiber–Reinforced Hybrid Composites: Effects of Biodegradation and Chemical Aging

The main goal of this study was to develop eco-friendly and low-cost multiple short natural fiber-reinforced hybrid composites with the hybridization of comparatively high-strength glass fibers. The hybrid composites were fabricated via hand lay-up by using short jute, silk, water hyacinth, and glass fibers for the reinforcements and unsaturated polyester resin for the thermoset polymer matrix. The reinforcing fibers were randomly oriented, and five types of hybrid composites were fabricated with different types of fiber content (wt.%). The performance of the manufactured hybrid composites was assessed by tensile, flexural, and impact testing, as well as water uptake (%). It was revealed that composites with high glass fiber content (wt.%) exhibited optimum mechanical performance in most cases, while poor moisture resistance performance was exhibited for the hybrid composites containing higher natural fibers (wt.%). The hybrid composite samples were also aged in soil medium (biodegradation) for 25 days and different chemical solutions (alkaline, acidic, and salt) for 10 days. After biodegradation, the drop of tensile strength (TS) and tensile modulus (TM) was revealed to be approximately 38–61 and 58–72%, respectively. On the other hand, after chemical aging, the drop of TS and TM was exhibited to be approximately 49–76% and 51–65%, respectively, for alkali solution aging; 42–75% and 29–76%, respectively, for acid solution aging; and 43–59% and 51–65%, respectively, for salt solution aging.

A novel experimental technique to determine the tack development during automated placement of uncured thermoset carbon/epoxy tows

In-situ bond strength toughness (IBST), commonly referred to as tow tackiness, is a first order property affecting the adherence quality and defect formation (e.g., wrinkles, folds) during automated tow placement (ATP) processing of uncured thermoset polymer matrix composite (PMC) tows. Tow-tow IBST develops over characteristic millisecond timescales (tc≤50ms) due to the rapid tow placement velocity of ∼1 m/s. In this paper, an experimental technique is presented to determine millisecond timescale tow-tow mode-I IBST in terms of fracture mechanics-based traction-separation relationship. The test specimen consists of two tows bonded to rigid platens with a pre-crack between them to induce crack initiation. Experiments are performed using IM7-G/8552 carbon/epoxy prepregs for both long and short timescales at a constant debonding rate of 5 mm/s, contact pressure of 0.23 MPa, and bonding temperature of 40 °C. In addition, high-speed two-dimensional digital image correlation (2D-DIC) is used to image and measure the tow-tow interfacial deformation during debonding. The peak traction and apparent energy release rate are found to significantly decrease (about 60 %) at the short millisecond timescale contact hold times compared to longer (i.e., second) timescale.

A treatise on mechanical properties of natural and synthetic fibre reinforced hybrid polymer composites

Hybrid composites have proved to be a potential material attracting large scale attention for applications such as in construction, automobiles, aerospace and locomotives. In this article, a treatise on the hybrid composites types, their diversity of properties, the effect of various fibre surface treatments on mechanical properties of natural fibres and possible natural and synthetic fibre combinations for a variety of applications is presented. The mechanical characterization (tensile, flexural and impact) of different combinations of natural and synthetic fibres in thermoplastic or thermoset polymer matrices along with the critical issues is also showcased. Although the importance of hybrid composites, mechanical properties and their applications are already available in the literature, enhancing damage tolerance and impact resistance has not been duly focused by the research community.

Fabrication and evaluation of polyurethane supported form‐stable PCMs

AbstractThe current research is oriented towards the development and assessment of the properties of the form‐stable phase change materials (PCMs), comprising of the thermoset polymer matrix (polyurethane, PU) enclosing capric acid (CA) as an active thermal energy storage (TES) component. The Fourier Transform Infrared Spectroscopy (FTIR) and Field‐Emission Scanning Electron Microscopy (FE‐SEM) have been used to characterize the chemical nature and morphological details of the developed PU‐based PCMs (PUPCMs). TES attributes and thermal stability of the resultant PCMs are evaluated by thermo‐analytical techniques such as Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). A thermal reliability test has been conducted to determine the phase change efficiency of the prepared PCMs. PUPCMs have been found to be suitable for TES applications, such as passive space heating or cooling building applications.

Valorization of bio‐calcium carbonate based Chamelea gallina shell waste fillers in shape memory polymer composites

AbstractIn recent years, the focus has been on the use of calcium carbonate‐based seashell wastes in the production of new thermoplastic and thermoset polymer materials, paving the way for their use as biofillers in polymeric composites. In this study, it is aimed to obtain a new polymeric composite material by doping Chamelea gallina shells, on polylactic acid (PLA)/polyethylene glycol (PEG) blend. Structural characterization of the obtained PLA/PEG blend/C. gallina composite films was performed with attenuated total reflection infrared spectroscopy (ATR‐IR). When the thermal properties of composite materials were examined by thermogravimetric analysis (TGA), it was determined that the thermal stability of polymeric composites increased with the addition of C. gallina. SEM images showed that the polymer blend films, which appeared to have a porous structure, filled the pores with increasing C. gallina ratio. It was observed that the biodegradability of PLA/PEG blend composite films decreased with increasing C. gallina shells addition. However, C. gallina had a positive effect on the swelling and water absorption capacities of polymeric composites. The increase in tensile strength and elongation at break values of PLA/PEG blend/C. gallina composite films with increasing C. gallina means that the mechanical properties of the polymer are improved.

Itaconic acid-based sustainable polyurethane covalent adaptable networks with robust mechanical, reshaping and UV-resistant properties based on reversible disulfide bond

Thermoset polymer materials are widely used in various fields due to their excellent performance brought by their permanently cross-linked structures. However, their inability to be recycled also leads to a serious waste of resources. The emergence of covalent adaptable networks (CANs) has solved the problem perfectly that thermoset materials are difficult to recycle. Meanwhile, with the increasing concern for resources and the environment, bio-based materials have sparked a research boom. Itaconic acid is a biomass feedstock with great prospects for development. In this study, itaconic acid, 1,6-hexanediol, 6-mercapto-1-hexanol, isocyanate, and 4,4′-dithiodiphenylamine were used as raw materials. Itaconic acid-based polyols were first synthesized by thiol-ene click reaction, and a series of itaconic acid-based polyurethane (PU) materials containing dynamic covalent networks were synthesized by varying the ratios between the amino and hydroxyl groups. The obtained material has good mechanical properties with a maximum tensile strength of 31.5 MPa and a modulus of 717 MPa. The presence of disulfide bonds allows the material to be recycled by remodeling, and the recovery efficiency of tensile strength after three remodeling cycles is 85.1 %. The material also has excellent solvent resistance and UV-blocking resistance. In conclusion, this work provides possible ideas for the high-value utilization of itaconic acid in polyurethanes.

Tensile and Shear Creep Behavior of Structural Adhesives: Experiments and Modeling

Structural adhesives characterized a turning point in the post-connection of structural elements due to their excellent performances and ability to transfer stress without losing their integrity. These materials are typically particle-reinforced composites made by a thermoset polymer matrix and fillers. During the in-situ application of this material, the thermal activation of the polymer is typically not possible, leading to an undefined degree of cure and therefore to a variation of the mechanical performance over time. This altering means that after applying a sustained load on a bonded anchor system installed at regular temperature, the adhesive changes material properties. Ample studies convince that the progressive increase of the degree of cure of the thermosetting polymer leads to higher strength and stiffness. However, limited studies have been dedicated to the post-curing effects on the long-term behavior. The main goal of this work is to investigate the tensile and shear creep behavior of two commercially available structural adhesives and the influence of curing conditions on their long-term performances. An extensive experimental campaign comprising short and long-term characterizations has been carried out on specimens subjected to three different curing and post-curing protocols, with the scope of imitating relevant in-situ conditions. The results demonstrate that structural adhesives cured at higher temperatures are less subjected to creep deformations. As a material equation, the generalized Kelvin model is utilized to fit the tensile and shear creep data, and two continuous creep spectra have been selected to represent the creep behavior and facilitate extrapolations to the long-term behavior.

Thermoset-polymer matrix composite materials of jute and glass fibre reinforcements: Radiation effects determination

In this work, woven jute and glass fabrics were used as natural fiber and synthetic fiber reinforcements, respectively, and unsaturated polyester resin was used as a thermoset polymer matrix to fabricate jute/polyester and glass/polyester composites via compression molding. As expected, glass/polyester exhibited superior performance than jute/polyester composites in terms of mechanical properties and moisture uptake behavior. Further, both composite laminates were exposed to gamma (γ) irradiation at a dose of 5 kGy to enhance their performance. After γ-irradiation, it was revealed that tensile strength, bending strength, tensile modulus, bending modulus, and impact strength increased by approximately 14, 28, 20, 21, and 13%, respectively, for the case of jute/polyester composites while glass/polyester composites demonstrated 13, 27, 15, 14, and 22% increase of the values, respectively. Further characterization of the composite samples was performed via moisture uptake in water and salt solutions, Scanning Electron Microscopy (SEM), and Energy Dispersive Spectrum (EDS) analysis.

Effect of Alternating Hybridisation of Fibres on the Physico - Mechanical Behaviour of Composite Materials

Abstract The performance/weight ratio of fiber reinforced polymer matrix composites makes them the material of choice for structural applications in many fields such as aerospace, aeronautics, automotive and civil engineering...etc. In polymer matrix composites, the fibers used as reinforcement are mainly synthetic fibers such as carbon and/or glass fibers. To ensure the low cost of using fiber-reinforced materials in motor vehicles, it is proposed to selectively incorporate carbon fibers to enhance glass fiber composites along the roadway, and to enhance glass fiber composites along the main load path. For this purpose, we conducted a behavioral study of hybrid epoxy thermoset polymer matrix laminates to highlight the influence of alternate hybridization of glass and carbon fibers on the physical-mechanical behavior of the materials.The results obtained show that the alternated hybridation of the fibers has a significant influence on the tensile properties; and it affected the density, hardness and flexural properties significantly.

Design, manufacturing, and elastic analysis of digital light processing 3D printed fiber reinforced sandwich beams with thermosetting polymer matrix

For the first time, a digital light processing (DLP) three-dimensional (3D) printer is implemented for additive manufacturing of sandwich beams with fiber reinforced facesheets and different core types without using adhesives. After characterizing the formulated thermosetting resin, sandwich beams with honeycomb and square core unit cells were printed in out-of-plane (OP) and in-plane (IP) arrangements, with and without woven glass fiber reinforcement in the facesheets. Meanwhile, using theoretical, micromechanical, and finite element (FE) approaches, the elastic properties and stiffness of sandwich beams were predicted. The stiffness measured from flex tests showed reliable agreement with predictions from analytical and finite element analysis (FEA) for most cases. Additionally, fiber reinforcement significantly increased specific stiffness of these structures, but did not affect the trends for different core geometries. The novel methodology presented here can open new doors for manufacturing advanced structures using DLP 3D printing technology.

Effect of thermoplastic impregnation on the mechanical behaviour of textile reinforcement for concrete

In recent decades, textile reinforced concrete (TRC) has become increasingly important, both in research and the construction industry. It is a resource-efficient material alternative to conventional, steel reinforced concrete due to the use of non-corroding high-performance textile reinforcements and the resulting material savings. Typically, thermoset polymer materials are used as impregnation for the textile reinforcement to improve the mechanical behaviour. However, due to their chemically crosslinking behaviour, these materials prevent subsequent product-specific shaping of the reinforcement. The use of thermoplastic impregnation materials shows potential to allow shaping by utilizing the thermal forming behaviour, provided that the resulting properties of the reinforcement system in terms of mechanical performance are not inferior to those of the already available impregnations. In this study, four impregnation systems are investigated on AR-glass textiles with regard to their effect on the mechanical behaviour of the reinforcement and classified in comparison to the current benchmark epoxy and styrene butadiene rubber (SBR) by conducting single yarn tensile tests and supporting microscopy analysis. The thermoplastic impregnation increased the tensile strength of the AR glass fibre to values in the range of around 1200 MPa with a low coating content to 1500 MPa with a high coating content. A strong dependence of the impregnation efficiency on the impregnation composition, in this case the solid content of the dispersion, was demonstrated as a result of pore formation. In conclusion, thermoplastic impregnation materials achieve strengths comparable to those of commonly used materials.

Repeatable self-healing of composite’s fatigue delamination

This paper investigates repeatable self-healing of composite laminates to mitigate fatigue delamination where a two-step healing mechanism is employed to heal the delamination cracks in a CFRP composite: (i) close the cracked surfaces by thermally activating dispersed shape memory polymer (SMP) filaments, and (ii) heal the closed crack by melting the thermoplastic healant (PCL) dispersed in the thermoset polymer matrix and allowing it to flow into the cracked region and solidify. Repetitive self-healing is carried out on double cantilever beam (DCB) specimens using macro fiber composite (MFC) actuators bonded to the test specimens, which generate the heat required to activate the thermoplastic healants to heal the delamination in the composite. Fatigue delamination growth rates were obtained for replicate specimens to extract statistically meaningful data on fatigue life under mode-I loading after seven healing cycles, indicating substantial retardation in delamination growth rate resulting in a significant increase in fatigue life.

A study on use of fibre reinforced plastic (FRP) connecting rod in IC engines

Innovation and constant competition in the automobile sector fuels the need for modifying or replacing the existing automobile components with high strength and lightweight materials to attain increased energy efficiency. One such automobile component considered in this work is the engine connecting rod which is a high volume production critical component. An engine connecting rod typically experiences a strong axial force due to the movement of engine piston on its one end and on the crank shaft on the other end. Such a force causes high stress and at times leads to failure of this critical component. To counter this force, high strength steel is used to make the connecting rod have high rigidity and strength but makes it a heavy engine component leading to less fuel efficiency of the engine. Fibre Reinforced Plastics (FRP) have been a centre of attention in Automobile Engineering due to their “high strength to low weight” ratio. This work is about the fabrication of Glass Fibre Reinforced Plastic (GFRP) engine connecting rod which is made of glass fibre with a suitable thermoset polymer matrix. The process of fabricating a FRP connecting rod is by a semi mechanized method with the continuous fibres oriented all along the entire component to counter all forces acting on the entire connecting rod thus making the rod much stronger. The major challenge in this work is fabricating the rod with the fibres aligned in its designated position and making it counter the forces which acts on it. The FRP connecting rod is more advantageous than the conventional steel rod both in terms of saving energy during its working condition and also during it’s manufacturing process by this simple semi mechanized way of manufacturing.

Development of a High-Fidelity Framework to Describe the Process-Dependent Viscoelasticity of a Fast-Curing Epoxy Matrix Resin including Testing, Modelling, Calibration and Validation.

Fast-curing epoxy resins enable substantial reduction of cycle times during production of thermoset polymer matrix composites. Due to the snap-cure behaviour, both characterisation and processing of these resins are associated with high complexity which motivates the development of a high-fidelity framework for the prediction of the process-dependent behaviour ranging from experiment to model validation. In order to determine influence of time, temperature, and degree of cure, a multitude of rheometer and dynamic mechanical analysis experiments are conducted and evaluated. Building on the experimental results, a material model based on a generalised Maxwell model is developed. It is calibrated on the results obtained in the tests and shown to describe the material’s behaviour with high accuracy under all investigated conditions. The model’s predictive capabilities are further tested by applying it to a dynamic mechanical analysis, exposing the model to previously unknown loading and temperature conditions. It is demonstrated that the model is capable of predicting such changing boundary conditions with high accuracy.

Experimental investigation on the effect of fiber volume fraction of sponge gourd outer skin fiber reinforced epoxy composites

AbstractNatural fibers have gained popularity as composite reinforcements in recent years. Matured sponge gourd has a fibrous structure consisting of inner core and outer shell (skin). Several studies were done on the inner core as reinforcement in the various thermoplastic and thermoset polymer matrices. In the current experimental study, the fibers were extracted from the outer skin of the matured sponge gourd used as reinforcement in the epoxy matrix. Extracted sponge gourd outer skin fibers (SGOSF) were cut into short fibers then reinforced with the epoxy resin and the composites were manufactured by compression molding method. The fiber volume fraction varies from 10 to 50 wt% reinforced with epoxy matrix and the composites were characterized by mechanical, thermal, and water absorption characteristics. The results revealed that 40 wt% SGOSF reinforced composites have higher tensile, flexural, compressive, and impact strengths and hardness when compared to other prepared composite materials. It is found from the thermal study results that the developed composite can withstand up to 340°C higher temperature than neat epoxy. The matrix/fiber bonding and void content were analyzed by scanning electron microscopy (SEM) analysis.