Polymer Matrix Composite Structures Research Articles

Extraction and characterization of a new natural cellulosic fiber from the Habara Plant Stem (HF) as potential reinforcement for polymer composites

In this present work, characterize the chemical, physical, thermal and Morphological behaviour of raw and alkali-treated (NaOH 5 %,10 % & 15 %) new natural cellulose Habara plant stem fiber (HF). From the chemical analysis, the 10 % alkali-treated HF obtained cellulose (67.9 %), hemicellulose (12.7 %), lignin (11.8 %) wax (0.18 %), moisture (2.44 %) and Ash (1.21 %). Fourier Transform Infrared Spectroscopy Analysis, alkali treatment effectively eliminates hemicellulose and lignin from the surfaces of natural fiber, as seen changes in the FTIR peaks at 1730, 1480, and 1140 cm−1.The X-ray analysis results indicate that, there is crystalline cellulose present, with a crystallinity level of 43.87 %, and that the other components are amorphous. In addition, the thermal stability of lignocellulosic fiber up to 230 °C was observed, and the degradation steps of each major component could be identified. The 10 % alkali-treated HF provides tensile strength of 790.9 MPa, with an elongation at break of about 3.41 %. The Scanning Electron Microscope analysis showcased the morphological changes on the fiber fractured surface, diameter variation, and impurities, etc. The Atomic Force Microscopy was used to determine the surface roughness characteristics of the HF, which confirmed the possible reinforcement in the structure of the polymer matrix composite structure.

Direct ink writing of polymer matrix composite with carbon for driving a flexible thermoelectric actuator of shape memory polymer

Carbon nanomaterials and polymer composites that possess excellent electrical and mechanical properties for soft robots have been investigated over decades in multidisciplinary research fields. As considering the incorporation of carbon into polymer composite, several major concerns include the electrical conductivity, elastic module, and manufacturing flexibility that can enable them to satisfy various functions such as actuation and sensing. In this paper, we report a comprehensive study on how to design and fabricate a soft gripper based on carbon polymer matrix composite and multilayer structure through multistep processes of 3D printing on paper. Using commercial conductive additives of graphene and carbon nanotube with polydimethylsiloxane (PDMS), a polymer matrix composite (PMC) was prepared for the ink of direct ink writing (DIW) with percolation conductivity. Additionally, a shape memory polymer (SMP) was utilized for fused deposition modeling (FDM) of a thermal actuator. Incorporating the DIW of PMC with the FDM of SMP on paper, a soft gripper with four fingers was designed and fabricated to show remarkable thermoelectrical actuation for grasping a 50 mm-diameter 10 g-weight spherical ball. In the future, it would provide an alternative approach for the fields of science and engineering, such as nanomaterials and nanotechnology, space applications, sustainable soft robots, and flexible autonomous systems.

A Novel Framework for Qualification of a Composite-Based Main Landing Gear Strut of a Lightweight Aircraft

The determination of suitable testing and qualification procedures for fiber-reinforced polymer matrix composite structures is an active area of research due to the increased demand, especially in the field of aerospace. This research illustrates the development of a generic qualification framework for a composite-based main landing gear strut of a lightweight aircraft. For this purpose, a landing gear strut composed of T700 carbon fiber/epoxy material was designed and analyzed for a given lightweight aircraft having mass of 1600 kg. Computational analysis was performed on ABAQUS CAE® to evaluate the maximum stresses and critical failure modes encountered during one-point landing condition as defined in the UAV Systems Airworthiness Requirements (USAR) and Air Worthiness Standards FAA FAR Part 23. A three-step qualification framework including material, process and product-based qualification was then proposed against these maximum stresses and failure modes. The proposed framework revolves around the destructive testing of specimens initially as per ASTM standards D 7264 and D 2344, followed by defining the autoclave process parameters and customized testing of thick specimens to evaluate material strength against the maximum stresses in specific failure modes of the main landing gear strut. Once the desired strength of the specimens was achieved based on material and process qualifications, qualification criteria for the main landing gear strut were proposed which would not only serve as an alternative to drop test the landing gear struts as defined in air worthiness standards during mass production, but would also give confidence to manufacturers to undertake the manufacturing of main landing gear struts using qualified material and process parameters.

Recent Advances in Limiting Fatigue Damage Accumulation Induced by Self-Heating in Polymer-Matrix Composites.

The self-heating effect can be considered as a catastrophic phenomenon that occurs in polymers and polymer-matrix composites (PMCs) subjected to fatigue loading or vibrations. This phenomenon appears in the form of temperature growth in such structures due to their relatively low thermal conductivities. The appearance of thermal stress resulting from temperature growth and the coefficient of thermal expansion (CTE) mismatch between fibers and neighboring polymer matrix initiates and/or accelerates structural degradation and consequently provokes sudden fatigue failure in the structures. Therefore, it is of primary significance for a number of practical applications to first characterize the degradation mechanism at the nano-, micro- and macroscales caused by the self-heating phenomenon and then minimize it through the implementation of numerous approaches. One viable solution is to cool the surfaces of considered structures using various cooling scenarios, such as environmental and operational factors, linked with convection, contributing to enhancing heat removal through convection. Furthermore, if materials are appropriately selected regarding their thermomechanical properties involving thermal conductivity, structural degradation may be prevented or at least minimized. This article presents a benchmarking survey of the conducted research studies associated with the fatigue performance of cyclically loaded PMC structures and an analysis of possible solutions to avoid structural degradation caused by the self-heating effect.

Effect of shape on depth profile Nuclear Magnetic Resonance data of multilayered composite structure

ABSTRACT Polymer matrix composite structures with adhesively bonded rubber layers are being used for various industrial applications. The adhesive layer thickness (used for bonding composite and elastomer rubber layers) has to be uniform to achieve desired bond strength. However, this cannot be controlled in practical applications in industry as no physical measurements are possible for large structures. This paper reports application of single-sided portable Nuclear Magnetic Resonance (NMR) at a frequency of 12.88 MHz for the study of the adhesive layer thickness measurement as well as qualitative analysis of the adhesive layer used for bonding these materials. The effect of the shape of the sample on the proton NMR signal which is related indirectly to elastic properties was investigated. Results obtained on flat and curved glass fibre reinforced polymer (GFRP) composite samples were compared. Studies showed there is a change in single-sided NMR depth profile data (slope of amplitude versus depth curve) due to changes in the shape of the composite structure. A multilayer sample with rubber and propellant bonded adhesively to the composite structure was also tested to study the effect of shape on the profile NMR data.

Investigation of Physicochemical Properties and Characterization of Leaf Stalk Fibres Extracted from the Caribbean Royal Palm Tree

Synthetic fibres (SF) are replaced by natural fibres (NF) and are utilized as polymer reinforcement owing to their eco-friendliness. The composite has been introduced in the current development by employing NF as reinforcement and stuffing in the polymer matrix (PM). The advantages of using natural resources are being eco-friendly, having plentiful natural availability, higher strength, lower cost, and a simple extrication process. When heated to a specific temperature, certain synthetic products create noxious materials. Therefore, replacing these synthetic substances with natural substances has greater advantages for the environment. In this study, a novel NF extricated from the Caribbean royal palm (CRP) along with its features is determined to replace the harmful SF effectively. The CRP’s leaf stalks, termed CRP leaf stalk fibres (CRPLSFs), are extricated and categorized by (i) thermogravimetric analysis (TGA), (ii) scanning electron microscopy (SEM), (iii) Fourier-transform infrared (FT-IR) spectroscopy, (iv) physical-chemical analysis, (v) X-ray diffraction (XRD), and (vi) tensile test (TT). The physical-chemical characteristics of CRPLSFs, cellulose content (CC), tensile strength (TS), density, and hemicelluloses correlate with other NF characteristics. The CRPLSFs’ chemical components include hemicelluloses (14.52%), lignin (9.15%), and cellulose (61.67%). The TGA shows that the CRPLSFs are thermally stabilized up to 326°C. The XRD proved that the CRPLSFs are enriched with a cellulose fraction comprising a crystallinity index (CI) of 30.27%. The outcomes recommended that the biodegradable coconut peduncle leaf stalk fibres (CPLSF) could be exploited as possible reinforcement in the PM composite structure and can be engaged in making composites.

Cold spraying on polymer-based composites: Understanding the single-particle adhesion

The metallization of the polymer matrix composite structures arises from the need to overcome some of the limits of the polymer-based materials, such as poor thermal and electrical conductivity. The cold spray technology has proved to be one of the most valid solutions for this scope. While the adhesion mechanisms of metal particles on metallic substrates are quite well known, the phenomena occurring when cold spraying on polymers are far to be understood. In this scenario, this paper proposes an interpretation of the phenomena leading to adhesion in cold spraying of metal particles onto polymer-based substrates, including composites. The aim is to try to unveil the phenomena ruling the adhesion by proposing a theoretical model conceived by conjecturing the phenomena occurring. The main hypothesis is that the adhesion is influenced by several energy-activated phenomena: the plastic deformation of the polymer, the plastic deformation of the particles and the loading of the fibers are conjectured to be the most influencing factors. So, the idea is to try to identify the most likely to occur phenomena based on an energy balance. A theoretical model is developed and validated through a dedicated experimental campaign to verify the effectiveness of the model to provide sufficiently reliable results. The model is applied to literature cases and the outcomes obtained are discussed to elucidate the adhesion mechanisms and the role of the fibers in fiber-reinforced polymers.

Production of different metal oxide nanoparticle embedded polymer matrix composite structures by the additive manufacturing technology and investigation of their properties

AbstractMetal oxide nano additives are widely used as a second phase modifier as they improve the properties of the matrix materials. Nano additives also supply various advantages for polymers which can be employed in additive manufacturing methods. Among the additive manufacturing methods, stereolithography is one of the most remarkable to produce nano‐modified polymers because of the easy nano modification of the photocurable resins. In the present study, we mixed the metal oxide particles; Fe2O3, ZnO, NiO, Al2O3, TiO2, and MgO with the photocurable epoxy and used the mixtures to print the specimens. We investigated the structural morphology, thermal and mechanical properties of the printed specimens with an optical microscope, scanning electron microscope, Fourier transform infrared spectroscopy, differential scanning calorimeter, differential thermogravimetric analysis, and microhardness, respectively. Findings proved the dilute agglomeration of the nano additives. Besides, nano additives can improve the thermal stability of the photo‐cured polymer. The microhardness of the Fe2O3 added polymers reached 27.63 HV levels while it was measured as 16.16 HV for the pristine samples (~70% raise was experienced). The maximum degradation temperatures of the polymer nanocomposite structures were measured in the range of 396–420 °C.

Extraction and Characterization of Agricultural Discarded Sesbania Aculeata Stem Waste as Potential Alternate for Synthetic Fibers in Polymer Composites

ABSTRACT Natural fibers have a wide range of potential applications in green composite manufacturing industrial sectors due to their renewable eco-friendly nature and remarkable properties. In the present work, the physico-chemical, thermal, tensile and morphological properties of Sesbania Aculeata Fibers (SAFs) are presented in first time. Chemical analysis results show that SAFs have relatively higher α-cellulose (70.1 wt.%) with lower hemicelluloses (10.2 wt.%), lignin (12.1 wt.%) and wax (0.6 wt.%) content. Structural analysis of SAFs was performed through fourier transform infrared (FTIR), energy dispersive X-ray microanalyzer (EDX) and NMR spectroscopy. X-ray diffraction (XRD) analysis evidenced that SAFs have a crystallinity index (CrI) of 65.5% with a crystalline size of 4.6 nm. The mechanical properties of the SAFs were investigated through a single fiber tensile test and fiber pull out test. The thermal stability of the SAFs was examined by thermogravimetric analysis (TGA). Based on the results, it is predicted that the SAFs can be used as a potential reinforcement in the polymer matrix composite structure.

Influence of 3-D periodic stitching patterns on the strain distributions in polymer matrix composites

This study investigates the effects of periodic stitching patterns on the strain distribution of three-dimensional (3-D) stitched carbon composite structures. Quasi-isotropic composite specimens with three different periodic stitching patterns (0°, 45°, and 90°) were fabricated and tested under uniaxial loading. Surface strain fields were obtained using digital image correlation (DIC). Different strain distributions developed between the front and back of the stitch seams in the stitched specimens. Higher strain concentrations developed in a direction perpendicular to the in-plane stitching except in the case of the 45° stitched specimens, where strain concentrations developed in both the longitudinal and transverse directions. The stitch seam geometry on the front side of the stitched specimens produced a significantly lower Poisson’s ratio compared to the back side. The load–displacement behavior and the tensile modulus were altered due to stitching and were found to increase with the stitch angle. This behavior indicates that stitching can give rise to localized zones of altered modulus of elasticity, which can be beneficial in tailoring the mechanical properties of polymer matrix composite structures.

Experimental Study of the Probabilistic Fatigue Residual Strength of a Carbon Fiber-Reinforced Polymer Matrix Composite

Degradation of the mechanical properties of fiber-reinforced polymer matrix composites (PMCs) subjected to cyclic loading is crucial to the long-term load-carrying capability of PMC structures in practice. This paper reports the experimental study of fatigue residual tensile strength and its probabilistic distribution in a carbon fiber-reinforced PMC laminate made of unidirectional (UD) carbon-fiber/epoxy prepregs (Hexcel T2G190/F263) with the ply layup [0/±45/90]S after certain cycles of cyclic loading. The residual tensile strengths of the PMC laminates after cyclic loading of 1 (quasistatic), 2000, and 10,000 cycles were determined. Statistical analysis of the experimental data shows that the fatigue residual tensile strength of the PMC laminate follows a two-parameter Weibull distribution model with the credibility ≥ 95%. With increasing fatigue cycles, the mean value of the fatigue residual strength of the PMC specimens decreased while its deviation increased. A free-edge stress model is further adopted to explain the fatigue failure initiation of the composite laminate. The present experimental study is valuable for understanding the fatigue durability of PMC laminates as well as reliable design and performance prediction of composite structures.

Evaluation of a polymer-steel laminated sheet composite structure produced by friction stir additive manufacturing (FSAM) technology

Laminated polymer-steel composites are promising layered materials for practical applications in the automotive industry considering their superior crush resistance capacity in terms of enhanced damping potential. In this research, the sheet lamination (SL) route of friction stir additive manufacturing (FTAM) technology was implemented for the production of a poly-methyl-methacrylate (PMMA) polymer matrix composite structure as reinforced by textile stainless steel layers, and feeding of PMMA granulates inside the stirred region. Layers bonding and the soundness of composite formation during fabrication of the laminated structure were studied. Possible chemical interactions between the steel and PMMA during friction stir mixing followed by solid-state consolidation of composite layers were characterized by X-ray photoelectron spectroscopy (XPS) analysis. The results revealed some evidence for dipole bonding between iron with oxygen and carbon elements. Orientation dependency of polymer-steel sheet laminated composite structures was demonstrated by universal tensile testing and flexural bending from different sections and fractographic analyses. Superior flexural bending (around 90% of PMMA) was shown for the produced layered structure.

Investigation on Ultrasonic Welding Attributes of Novel Carbon/Elium® Composites.

Joining large and complex polymer–matrix composite structures is becoming increasingly important in industries such as automobiles, aerospace, sports, wind turbines, and others. Ultrasonic welding is an ultra-fast joining process and also provides excellent joint quality as a cost-effective alternative to other joining processes. This research aims at investigating the welding characteristics of novel methyl methacrylate Elium®, a liquid thermoplastic resin. Elium® is the first of its kind of thermoplastic resin, which is curable at room temperature and is suitable for mass production processes. The welding characteristics of Elium® composites were investigated by optimizing the welding parameters with specially designed integrated energy directors (ED) and manufactured using the Resin transfer molding process. The results showed a 23% higher lap shear strength for ultrasonically welded composite joints when compared to the adhesively bonded joints. The optimized welding time for the ultrasonic welded joint was found to be 1.5 s whereas it was 10 min for the adhesively bonded joint. Fractographic analysis showed the significant plastic deformation and shear cusps formation on the fractured surface, which are typical characteristics for strong interfacial bonding.

Strength and fracture behaviour of polymer matrix composite layered structures made by additive manufacturing

In this paper, studies on the tensile strength, fracture initiation and propagation behaviour of composite material layered shell structures manufactured by extrusion based additive manufacturing (AM) is reported. To understand the basic mechanical behaviour, simple tension tests have been conducted on ASTM-D638 specimens of carbon fiber and natural fiber reinforced polymer matrix composites made by AM in different modes as well as directly in filament form using a filament extruder. The tensile strengths reveal that the internal defects unique to additive manufacturing, such as lack of fusion (LOF) sites and voids, play crucial role in the macroscopic fracture. Based on the tensile test results, finite element analysis of shell structures typical of below-knee prosthetic sockets has been conducted to predict the fracture initiation sites and propagation paths. The analysis results have shown close correlation with the experimental observation of the fracture phenomenon in the prosthetic sockets given to pilot test amputees.

Integrated self-monitoring and self-healing continuous carbon fiber reinforced thermoplastic structures using dual-material three-dimensional printing technology

Polymer-matrix composite structures with both self-monitoring and self-healing properties are proposed using a dual-material additive manufacturing technique. A double-nozzle three-dimensional (3D) printer system was adopted to fabricate these composite structures. A thermoplastic matrix with healing-agent containers was printed using one of the nozzles. The continuous carbon fibers, serving as both a sensory element and reinforcement, were embedded into the thermoplastic matrix using the other nozzle. The feasibility and effectiveness of the structures were verified through compression and three-point bending tests. Real-time self-monitoring of structural damage was performed using electrical resistance measurements. The results demonstrated that addition of 2120 Epoxy Cure agent and 2000 Epoxy Resin agent into the polymer matrix could help to repair the structural damage, with average healing efficiencies of 27.84% for non-reinforced specimens and 30.15% for fiber-reinforced specimens. In addition, digital image correlation (DIC) was utilized to analyze the reinforcing mechanism and failure behavior of the 3D printed thermoplastic composite structures reinforced with continuous carbon fibers. Integration of continuous carbon fibers and healing agents within the polymer matrix can create smart structures that can not only monitor their own structural health state, but also repair structural damage.

Micromechanical modeling of the effects of adiabatic heating on the high strain rate deformation of polymer matrix composites

Fiber reinforced polymer matrix composites are increasingly being used to fabricate energy-absorbing aerospace structural components susceptible to impact loading, such as jet engine containment structures subjected to blade-out events. The development and certification of such structures necessitates a detailed understanding of the dynamic behavior of the constituent materials, particularly the strain rate, temperature, and pressure dependent polymer matrix, and their complex interaction. As the rate of deformation increases, the thermodynamic condition transitions from isothermal to adiabatic. The conversion of plastic work to heat causes local adiabatic heating in the polymer matrix, but the rapid nature of impact events does not allow sufficient time for heat to dissipate; ballistic impact events can therefore be regarded as fully adiabatic. Local adiabatic heating can significantly affect the high rate deformation response if thermal softening effects outweigh strain and strain rate hardening effects and therefore, must be explicitly modeled at the appropriate length scale. In this paper, an existing isothermal viscoplastic strain rate and pressure-dependent polymer constitutive formulation is extended to nonisothermal conditions by modifying the inelastic strain rate tensor components to explicitly depend on temperature based on the Arrhenius equation for nonisothermal processes. A methodology based on shifting neat resin dynamic mechanical analysis data is utilized to determine the polymer elastic properties over a range of strain rates and temperatures. Temperature rises due to the conversion of plastic work to heat are computed, assuming adiabatic conditions. It is demonstrated that the modified polymer constitutive model is capable of capturing strain rate and temperature dependent yield as well as thermal softening associated with the conversion of plastic work to heat at high rates of strain. The nonisothermal polymer constitutive model is then embedded within the Generalized Method of Cells micromechanics framework to investigate the manifestation of matrix thermal softening, due to the conversion of plastic work to heat, on the high strain rate response of a T700/Epon 862 unidirectional composite. Adiabatic model predictions for high strain rate composite longitudinal tensile, transverse tensile, and in-plane shear loading are presented. Results show a substantial deviation from isothermal conditions; significant thermal softening is observed for matrix dominated deformation modes (transverse tension and in-plane shear), highlighting the importance of accounting for local adiabatic heating in the polymer matrix in the high strain rate analysis of polymer matrix composite structures.

Large-scale deformation and damage detection of 3D printed continuous carbon fiber reinforced polymer-matrix composite structures

For the efficient monitoring regional deformation and damage of continuous carbon fiber reinforced polymer-matrix composite structures, a dual-material three-dimensional printing process was developed, in which continuous carbon fiber tows were integrated within the polymer matrix to construct smart sensing grids. Strategies based on the electrical-mechanical behavior of continuous carbon fiber tow for locating loading position and recognizing deformation field distribution, as well as damage detection, have been presented. The loading location can be determined through the maximum fractional change in electrical resistance of continuous carbon fiber tows in the longitudinal and transverse direction. A model based on the electrical-mechanical behavior of carbon fiber tow has been developed to identify the deformation field distribution. Both micro-damage and macro-damage can be detected according to the dramatic change in the slope of fractional change in electrical resistance with the strain. The effectiveness of above methods has been verified through experiments.

Seawater ageing effect on the mechanical properties of composites with different fiber and matrix types

The use of fiber-reinforced composites in marine applications such as components of tidal turbines and wave energy converters is becoming attractive because of their reduced weight and improved corrosion resistance. However, when these polymer matrix composite structures are exposed to seawater environment, degradation of material properties is produced affecting reliability. A deep understating of seawater ageing effect on composite structures is essential to ensure long-term performance and durability. A systematic investigation was conducted in this work to evaluate the effect of seawater ageing on mechanical properties of five different composites manufactured with two types of fiber fabrics (unidirectional glass and carbon) and three types of resin systems (epoxy, vinylester and polyester). The behavior of samples with and without accelerated seawater ageing and subjected to tensile, compressive, flexural and shear loading was evaluated. A significant strength reduction due to seawater ageing was observed on composites with epoxy and polyester matrices. Low strength and stiffness values of composites with vinylester matrix are in general observed; however, seawater ageing makes these properties increase slightly. Fracture surface examination by scanning electron microscopy revealed delamination, fiber debonding and resin crumbling due to seawater effect.

Analysis of defect detectability in polymeric composites using self-heating based vibrothermography

The self-heating based vibrothermography (SHVT) is a new non-destructive testing method dedicated for testing of polymer matrix composite structures, where the excitation is performed by externally applied mechanical vibrations in a low frequency range. Exciting a structure with several resonant frequencies, the heating up of this structure is possible due to the occurrence of the thermoviscoleastic effect called the self-heating, whose nature originates from the mechanical energy dissipation. In order to examine an efficiency of the SHVT an analysis of defect detectability on composite specimens with milled artificial defects was performed. The post-processing of the series of resulting thermograms was performed in order to enhance defect detectability. The obtained results allow to conclude about high efficiency of SHVT NDT technique, which can be used especially in cases when a direct access to the testing structure in order to excite it externally is difficult or impossible.

Characterization of tensile property of high-performance fiber bundles combined with epoxy resin using advanced video extensometer

The increased desire to use high-performance fibers in the fields of industry and aerospace requires better understanding of their mechanical behaviors, especially in polymer matrix composite structure. By means of an advanced video extensometer using digital image correlation, the tensile properties of six kinds of high-performance organic and inorganic fiber bundles combined with epoxy resin were successfully determined in this paper, which have testing difficulties using contacting extensometer because of curved surface and small diameter of sample. The advanced video extensometer system was initially used for three kinds of carbon fibers impregnated and cured with epoxy resin to determine the optimum experimental conditions. The comparative tests demonstrate that the accuracy of the results is affected by light source and sampling frequency, but independent on crosshead speed. The tensile properties of other five kinds of epoxy impregnated fibers were subsequently measured using optimal conditions. The results show excellent agreement with the measurement of contacting dynamic extensometer for all studied fibers, and both relative error of Young’s modulus and elongation at break are in acceptable ranges. The capability of the advanced video extensometer system to record real-time, high-accuracy, and complete strain enables it to directly measure elongation. Then, Young’s modulus at different strain ranges was further studied. Different changing trends of Young’s modulus of various impregnated fibers with increasing strain were seen, which are related to the changes of fiber structure during testing.