Reinforced Epoxy Matrix Composites Research Articles

Micromechanical Analysis of the Fibre-Reinforced-Epoxy Composites with Nanoparticles Embedded in the Interphase Region under Transverse Compression

The mechanical behaviours of fibre reinforced epoxy matrix composites with silica nanoparticles inserted between fibres and matrix subjected to transverse compression are studied by computational micromechanics. A series of representative volume elements of composite microstructures containing fibres, nanoparticles with different distribution types, volume fractions and Young’ modulus; and matrix are established. The effect of nanoparticles incorporated in the interfacial phase on the elastic-plastic behaviour of composites has been assessed. The stress versus strain relationship, ductility and compressive strength are determined by the finite element analysis. It is found that the material property, volume fraction and distribution type of nanoparticles have significant influences on the mechanical behaviour of composites. The large plastic deformation between the fibre and nanoparticles can consume considerable deformation energy, which will enhance the mechanical behaviour of composites.

Effect of perlite particle contents on delamination toughness of S-glass fiber reinforced epoxy matrix composites

Abstract The effects of perlite particulate-filler on the mode I and mode II interlaminar fracture and mechanical behavior of glass fabric/epoxy composites were studied. Composite specimens for double-cantilever beam (DCB), end-notched flexure (ENF) tensile and flexural tests were prepared and tested according to ASTM standards with perlite contents of 1, 3, 5 and 10 wt%. The optical and scanning electron microscopes images were described the mechanisms of mode I and II interlaminar fracture. The results indicated that the mode I and mode II interlaminar fracture toughness were optimum at perlite content of 3 wt% with increment of 39.9% and 72.3%, respectively. The tensile strength and flexural properties reached maximum values at perlite content of 1 and 5 wt%, respectively.

Preparation and Characterization of Carbon Nanotube Deposited Carbon Fiber Reinforced Epoxy Matrix Multiscale Composites

In this study, desized carbon fibers were coated with carbon nanotubes using two diverse coating techniques, i.e. dip coating and spray up process, while the factors affecting the coating techniques were investigated. The morphological study revealed better nanotube coating on carbon fibers from dip coating technique as compared to spray up process. Later, nanotube-coated fibers from dip coating were impregnated with epoxy to fabricate multiscale carbon fiber reinforced epoxy matrix composites. The nanotubes on fiber surface were expected to improve the interlaminar shear properties of the multiscale composites. According to short beam shear testing, 14% increase in interlaminar shear strength was observed in composite containing nanotubes as compared to reference composite. Microscopic observation under optical and electron microscopes confirmed the void-free impregnation of fibers with epoxy along with the presence of nanotubes on fibers and in matrix in the vicinity of fibers. Finally, the mechanisms involving the enhanced interlaminar properties were identified and discussed.

Gamma Ray Shielding Property of Tungsten Powder Modified Continuous Basalt Fiber Reinforced Epoxy Matrix Composites

Continuous basalt fiber (BF) reinforced epoxy matrix composites with different contents of micro‐tungsten powder were fabricated by hot‐press process with prospective of combined radiation shielding and mechanical functions. Gamma photon shielding and mechanical properties of the composites were evaluated. The measured mass attenuation coefficient shows that tungsten filler significantly improves the radiation shielding property of BF composite, especially for low and moderate photon energies of 80 and 356 keV. Flexural strength of BF composite decreases along with increasing tungsten concentration, while flexural modulus and interlaminar shear strength are not obviously affected by tungsten content. Given the advantages of lightweight, high mechanical property and good radiation shielding performance, the studied BF/tungsten composite is promising material with integrated shielding and structural properties for use in nuclear industry. POLYM. COMPOS., 39:E2106–E2115, 2018. © 2017 Society of Plastics Engineers

Investigation of Mechanical Properties of Graphene and Reduced Graphene Oxide Reinforced Epoxy Matrix Composites

Abstract Graphene has generated great excitement in the scientific community due its unique mechanical and electronic properties, and also the availability of bulk quantities of graphene as both colloidal dispersion and powder. With the development of relatively high yield and defect-free synthesis methods, this exciting material is ready for practical application in the preparation of polymer nanocomposites. Here, we reported on the mechanical performances of epoxy nanocomposites which have been reinforced with exfoliated graphene nano platelet (GNP) and reduced graphene oxide (RGO) at a loading of 0 to 0.5 wt. %. A soft molding method was used for the preparation of epoxy nanocomposites. The reinforcing effects of GNP and RGO on epoxy resin were examined by tensile testing and dynamic mechanical analysis (DMA). The morphology of the epoxy/GO and epoxy/RGO nanocomposites were investigated using a scanning electron microscope (SEM). A significant improvement on mechanical properties of epoxy/GO and epoxy/RGO nanocomposites was observed at low GNP and RGO loading. Contrary to the literature, the ultimate tensile strength values have mainly decreased, although the Young’s modulus has improved. Dynamic mechanical analysis has shown that with the addition of both GNP and RGO, storage modulus was significantly enhanced at 40 °C. The loss factor was almost not affected by both RGO and GNP loading. SEM investigation of the fractured surface indicates that GNP and RGO fillers are dispersed uniformly in the epoxy matrix.

Recycling and characterization of carbon fibers from carbon fiber reinforced epoxy matrix composites by a novel super-heated-steam method

In order to manufacture high quality recycled carbon fibers (R-CFs), carbon fiber-reinforced composite wastes were pyrolysed with super-heated steam at 550 °C in a fixed bed reactor for varying reaction times. The mechanical and surface properties of the R-CFs were characterized with a single fiber tensile test, interface shear strength (IFSS), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The surface analysis showed that there was no matrix char residue on the fiber surfaces. The tensile strength and IFSS values of the R-CFs were 90% and 115% compared to those of virgin carbon fibers (V-CFs), respectively. The recycling efficiency of the R-CFs from the composites were strongly dependent on the pyrolysis temperature, reaction time, and super-heated steam feeding rate.

Radiation shielding property of structural polymer composite: Continuous basalt fiber reinforced epoxy matrix composite containing erbium oxide

For protecting human body and equipment against radiation in nuclear power industry, radiation medicine and aerospace exploration, advanced materials possessing good shielding capability, low density and high mechanical strength and modulus are in urgent demand. In this study, radiation protective basalt fiber (BF) reinforced epoxy matrix composite containing erbium oxide (Er2O3) particles was fabricated by prepreg-autoclave process, in order to make a novel mechanical/radiation shielding composite. For prepared unidirectional and quasi-isotropic BF/Er2O3 composite laminates, basalt fibers and Er2O3 particles distributed uniformly, and no obvious agglomeration of particles and defects were found. NaI(Tl) detector was used to test mass attenuation coefficient for evaluating X and gamma rays shielding performance at different photon energies ranging from 31 keV to 662 keV. The experimental results indicate that BF/Er2O3 composite shows good X and gamma rays shielding performance, and mass attenuation coefficient of BF/Er2O3 composite is much larger than that of aluminum in relatively low energy from 31 keV to 80 keV. The effect of prepreg stacking consequence on shielding performance was also discussed. In addition, to verify the applicability of classic “mixture role” on mass attenuation coefficient of anisotropic composites, theoretical mass attenuation coefficient at different photon energies was calculated using XCOM software based on the weight fraction and mass attenuation coefficient of each constituent element among BF/Er2O3 composite. It is found that there is maximum deviation of 10.3% between experimental and theoretical results. Thus, it is believed that the method is suitable for predicting shielding performance of continuous fiber reinforced composite materials. Considering the advantages in light weight and high mechanical property, the studied three-phase composite is promising for using in radiation shielding structure application.

Effect of high graphite filler contents on the mechanical and tribological failure behavior of epoxy matrix composites

This work evaluates the effect of the presence of high graphite contents on the mechanical and tribological properties of epoxy matrix and carbon fiber reinforced epoxy matrix composites. Epoxy matrix composites containing 0–30wt%-graphite were prepared by hand mixing. Graphite/epoxy fiber composites containing 0–11.5wt%-graphite were also prepared. The produced materials were characterized regarding mechanical properties, including experimental and numerical analysis, and sliding wear resistance. Experimental results show that the addition of high graphite amounts results in materials with increasingly high elastic modulus. However it also results in increased brittle behavior, significantly reducing failure strain for additions above 12.5wt%. Shear modulus and flexural shear modulus also increase with graphite addition. The presence of graphite in the epoxy matrix decreases subsurface fatigue wear and increases wear resistance, as a result of graphite lubricant action. Graphite/epoxy composites reinforced with carbon fiber present higher mechanical performance than conventional carbon fiber reinforced epoxy matrix composites. Attained results show that a maximum graphite concentration must be found to allow equilibrium between increased stiffness and wear resistance, and reduced fracture behavior. Nevertheless increasing graphite concentration above values commonly used in the literature appears to open an opportunity window for the processing of low cost hybrid materials combining high specific strength, increased conductivity and self-lubricant properties.

Dimeric anthracene-based mechanophore particles for damage precursor detection in reinforced epoxy matrix composites

The problem of catastrophic damage purveys in any material application, and minimizing its occurrence is paramount for general health and safety. We have successfully synthesized, characterized, and applied dimeric 9-anthracene carboxylic acid (Di-AC)-based mechanophore particles to form stress sensing epoxy matrix composites. As Di-AC had never been previously applied as a mechanophore and thermosets are rarely studied in mechanochemistry, this created an alternative avenue for study in the field. Under an applied stress, the cyclooctane-rings in the Di-AC particles reverted back to their fluorescent anthracene form, which linearly enhanced the overall fluorescence of the composite in response to the applied strain. The fluorescent signal further allowed for stress sensing in the elastic region of the stress–strain curve, which is considered to be a form of damage precursor detection. Overall, the incorporation of Di-AC to the epoxy matrix added much desired stress sensing and damage precursor detection capabilities with good retention of the material properties.

Effect of micro-Al2O3 contents on mechanical property of carbon fiber reinforced epoxy matrix composites

Abstract The effects of integrating micro-Al 2 O 3 onto carbon fiber surface and its contents on mechanical properties of carbon fiber reinforced polymer composites were investigated. Mode II interlaminar fracture toughness, impact strength, flexural properties and initial modulus were determined by mechanical test machines and dynamic mechanical analyzer. The reason for performance improvement was discussed based on scanning electron microscopy. The mode II interlaminar fracture toughness, impact strength, and flexural strength of composites without addition of micro-Al 2 O 3 were 348 J/m 2 , 118 kJ/m 2 and 682 MPa, respectively. However, the mechanical properties of modified composites were improved significantly. The mechanical properties were optimum when the areal density of micro-Al 2 O 3 particles reached 15 g/m 2 at which the mode II interlaminar fracture toughness, impact strength, and flexural strength reached 522 J/m 2 , 161.7 kJ/m 2 and 759 MPa, respectively. Furthermore, these composites with addition micro- Al 2 O 3 in the layers showed an improvement in thermal property.

An experimental study on mechanical properties of epoxy-matrix composites containing graphite filler

The current work studies the effect of the incorporation of different amounts of graphite filler on the mechanical properties of epoxy resin and of carbon fiber reinforced epoxy composites. Graphite-reinforced epoxy-matrix composites were prepared with graphite fractions ranging from 5 to 30 wt%. The carbon-fiber reinforced graphite/epoxy hybrids were prepared using a fixed amount of carbon fiber, and graphite incorporation in the epoxy of 7.5, 10 and 11.5 wt%. After cure the produced materials were submitted to tensile and to flexural three point bending tests. Examination of microstructural features and fracture surfaces were undertaken by optical microscopy and scanning electron microscopy. Increased graphite filler contents results in improved tensile modulus of the epoxy matrix. The 7.5, 10 and 11.5 wt%-graphite materials showed also an increase in the ultimate stress value with increasing filler. Introduction of reinforcement carbon fibers enhances tensile modulus. This increase is higher for the higher amounts of graphite filler in the matrix. This study shows that graphite/epoxy composites reinforced with carbon fiber present higher mechanical performance than conventional carbon fiber reinforced epoxy matrix composites.

Prediction of Tensile Strength of Unidirectional Carbon Fiber Reinforced Epoxy Matrix Composites with Spring Element Model

Prediction of Tensile Strength of Unidirectional Carbon Fiber Reinforced Epoxy Matrix Composites with Spring Element Model

Influence of electroless nickel-plating on fracture toughness of pitch-based carbon fibre reinforced composites

Nickel-Pitch-based carbon fibres (Ni-PFs) were prepared by electroless nickel-plating to enhance fracture toughness of Ni-PFs reinforced epoxy matrix composites (Ni-PFs/epoxy). The surface properties of Ni-PFs were determined by scanning electron microscopy (SEM), X-ray photoelectron spectrometry (XPS), and X-ray diffraction (XRD). The fracture toughness of the Ni-PFs/epoxy was assessed by critical stress intensity factor (KIC) and critical strain energy release rate (GIC). The fracture toughness of Ni-PFs/epoxy was enhanced compared to those of PFs/epoxy. These results were attributed to the increase of the degree of adhesion at interfaces between Ni-PFs and matrix resins in the composites.

Quasi-static behaviour and damage assessment of flax/epoxy composites

Experimental investigations were conducted on flax and E-glass fibres reinforced epoxy matrix composites subjected to quasi-static loadings. Flax/epoxy samples having [0]12, [90]12, [0/90]3S and [±45]3S stacking sequences, with a fibre volume fraction of 43% have been tested under tension, compression and in-plane shear loadings. Overall, the compression strength of glass/epoxy was 76% greater than for the flax/epoxy composite. The damage evolution of flax/epoxy of [0/90]3S and [±45]3S samples has been evaluated in terms of transverse crack densities with respect to the load increment. The crack density exhibited a classical “S” shaped pattern for [0/90]3S and linearly for [±45]3S specimens versus the applied load. The final crack densities were respectively of 32/cm and 25/cm for the [0/90]3S and [±45]3S samples.

Incremental mean-fields micromechanics scheme for non-linear response of ductile damaged composite materials

This work is concerned with the modeling of ductile damage behavior in composite materials by the means of the Incremental Micromechanics Scheme (IMS) as Mean-Fields Homogenization (MFH) technique. Indeed, IMS is known for its capability to overcome the well-known accuracy restrictions of the Mori–Tanaka (MT) and Self-Consistent (SC) schemes when a high volume fraction of heterogeneities or/and a high contrast between phases properties is reached. This micromechanics formalism is based on the Eshelby’s inclusion concept. The kinematic equation of Dederichs and Zeller (1973) is used as formal solution of the heterogeneous material problem. The nonlinear behavior of the composite is addressed in a general framework based on the kinematic hardening of Lemaıˆtre–Chaboche’s ductile damage model. Thus a classical J2 plasticity that accounts for the damage evolution within the microstructure is implemented. The time discretization of all rate relations is solved through a generalized mid-point rule that yields to an anisotropic consistent (algorithmic) tangent modulus. To avoid a stiffer macroscopic stress–strain response, an isotropization procedure is adopted during the computation of the Eshelby tensor involved in the IMS modeling. From a computational aspect, the non linear response of the composite is obtained through two interdependent loops: inner and outer. In the inner loop, the IMS determines the global strain concentration tensor that is passed to the outer loop. Then, the macroscopic stress–strain response is derived using an iterative algorithm based on the Hill-type incremental formulation. Numerical results are obtained considering several heterogeneous materials such as Metal Matrix Composites (MMCs) as well as Carbon fibers reinforced Epoxy Matrix Composites. The model’s predictions are compared in most of the cases, with experimental data and predictions obtained from MT-based modeling in the open literature.

Mechanical Properties of Chopped Randomly Oriented Epoxy - Luffa Fiber Reinforced Polymer Composite

This paper presents the study of the tensile, compressive, flexural, impact energy and water absorption characteristics of the luffa fiber reinforced expoxy polymer composites. Luffa fiber reinforced epoxy resin matrix composites have been developed by hand lay-up technique with varying process parameters such as fiber condition (treated and untreated), chopped randomly oriented and different volume fraction (30%, 40% and 50%). Tensile strength varies from 9 MPa to 20 MPa, compressive strength varies from 75 MPa to 105 MPa, flexural strength varies from 15 MPa to 140 MPa and impact energy varies from 0.25 Joules to 1.45 Joules, as a function of fiber volume fraction. The optimum mechanical properties were obtained at 40% of fiber volume fraction of treated fiber composites. Fracture surface of the composite shows that pull out and de-bonding of fiber is occurred.

Damage detection and self-repair in hollow glass fiber fabric-reinforced epoxy composites via fiber filling

Abstract Hollow glass fiber reinforced epoxy matrix composites were produced to study whether the damage development can be followed and the self-repair can triggered by filling the fibers with suitable additives. Composite plates were manufactured by the hand layup and vacuum assisted resin transfer molding techniques. To detect subcritical transverse impact damage, hollow fibers were filled with an ultraviolet fluorescent dye, whereas for self-repair, they were filled with a polyester resin along with the corresponding accelerator. The healing process was induced at different temperatures and continued for different durations. It was demonstrated that the targeted damage detection and self-repair can be achieved using thin (10–13 μm outer diameter) reinforcing hollow fibers. The self-repairing ability was demonstrated in three point bending tests and the healing was confirmed by inspection with scanning electron microscopy.

Fatigue behaviour of glass fibre reinforced epoxy composites enhanced with nanoparticles

Nanoparticle reinforcement of the matrix in laminates has been recently explored to improve mechanical properties, particularly the interlaminar strength. This study analyses the fatigue behaviour of nanoclay and multiwalled carbon nanotubes enhanced glass/epoxy laminates. The matrix used was the epoxy resin Biresin® CR120, combined with the hardener CH120-3. Multiwalled carbon nanotubes (MWCNTs) 98% and organo-montmorillonite Nanomer I30 E nanoclay were used. Composites plates were manufactured by moulding in vacuum. Fatigue tests were performed under constant amplitude, both under tension–tension and three points bending loadings. The fatigue results show that composites with small amounts of nanoparticles addition into the matrix have bending fatigue strength similar to the obtained for the neat glass fibre reinforced epoxy matrix composite. On the contrary, for higher percentages of nanoclays or carbon nanotubes addition the fatigue strength tend to decrease caused by poor nanoparticles dispersion and formation of agglomerates. Tensile fatigue strength is only marginally affected by the addition of small amount of particles. The fatigue ratio in tension–tension loading increases with the addition of nanoclays and multi-walled carbon nanotubes, suggesting that both nanoparticles can act as barriers to fatigue crack propagation.

Properties evolution of flax/epoxy composites under fatigue loading

The tension–tension fatigue behaviour of flax fibre reinforced epoxy matrix composites have been investigated for specimens having [0]12, [90]12, [0/90]3S and [±45]3S lay-ups. The Probabilized Stress–Number of cycles (P-S–N) curves have been determined for each laminate type. The measured stress and strain data allowed to quantify the evolution of the mechanical properties, i.e. stiffness, damping and permanent strain as a function of imposed cycles. Especially, the stiffening phenomenon of flax reinforcements oriented parallel to the loading direction has been confirmed. However, due to the competition between damage development and the fibre stiffening, the increase in the longitudinal Young’s modulus was noticed on the composites depending on the ratio of fibres parallel to load direction.

Mechanical Properties of Luffa Fiber and Ground nut Reinforced Epoxy Polymer Hybrid Composites

This paper presents the study of the tensile, compressive, flexural, impact energy and water absorption characteristics of the luffa fiber and Ground nut reinforced epoxy polymer hybrid composites. Luffa fiber and Ground nut reinforced epoxy resin matrix composites have been developed by hand lay-up technique with luffa fiber treated conditions and Ground nut with different volume fraction of fibers as in 1:1 ratio (10%, 20%, 30%, 40% and 50%). Effects of volume fraction on the Tensile, Compressive, Flexural, Impact strength were studied. SEM analysis on the composite materials was performed. Tensile strength varies from 10.35MPa to 19.31MPa, compressive strength varies from 26.66MPa to 52.22MPa, flexural strength varies from 35.75MPa to 58.95MPa and impact energy varies from 0.6 Joules to 1.3 Joules, as a function of fiber volume fraction. The optimum mechanical properties were obtained at 40% of fiber volume fraction of treated fiber composites. Fractures surface of the composite shows the pull out and de-bonding of fiber is occurred.