Particulate Epoxy Composites Research Articles

Moisture effects on vibration response of SMA particulate epoxy composite

ABSTRACT High performance composites are the need of the day owing to their high-tailorable high-specific properties. Various composites like particulate composites, FRP are extensively used for various engineering applications. Recently, attention is being paid on smart composites where smart materials are being incorporated in plastics for developing new group of composites to enable the usage of plastics in structural engineering applications. One example is the incorporation of SMA particulates in epoxy matrix. However, environmental conditions greatly influence polymer composite performance. Thus, experimental studies are carried out to study the effect on vibration characteristics of SMA particulate epoxy composite when exposed to sea and fresh water environments. To facilitate these experiments, a test rig is fabricated, in which vibrations are measured using ADXL345 accelerometer. Investigations indicated an increase in amplitude of vibrations with increase in moisture.

Experimental evaluation and comparison of silica/biocarbon particulate-epoxy composites for high-strength applications

Biowaste utilization and management are of primary concern in the current scenario for a sustainable environment. One way to enable this is to replace commercial fillers with composite materials. In the present study, the fillers, that is, silica and biocarbon are extracted from rice husk and processed further as biofillers for processing composites. With inherent processing challenges involved in biofiller-based composites, this study investigated and compared the influence of dispersed silica and biocarbon particles independently on the mechanical and tribological properties of epoxy composites. The composites were fabricated by a hand lay-up process. The composites were fabricated with three different filler loadings each of silica and biocarbon separately (2, 4 and 6 wt%). The mechanical characterization results illustrate that tensile, flexural, compression, and erosion wear showed superior properties compared to neat epoxy. It is also evident that there was an enhancement of 19% in compressive strength in composites compared to neat epoxy at 2 wt% silica and biocarbon filler composites. The tensile strength increased by 2.6 times when compared to neat epoxy at 2 wt% silica filler addition. Alongside, erosion results confirm that the properties of pure epoxy change from semi-brittle to ductile due to the addition of silica and biocarbon fillers. This semi-brittle to ductile nature is important for marine applications as propellers are subject to extreme cold and warm temperatures with very little transition time, leading to ductile to brittle failure. Finally, it can be inferred that silica extracted from rice husk has versatile applications when compared to the carbon extract.

Evaluation of Mechanical and Tribological Properties of Biowaste and Biowaste Based Silica Particulate Epoxy Composites

This paper reports the mechanical-erosion wear properties of extracted silica from Biowaste (rice husk) and pure rice husk-filled epoxy composites. A comparison is made on the influence of dispersed silica and rice husk particles on the properties of the epoxy composites. The composites are fabricated by hand lay-up process. The specimens are tested as per the ASTM standards for three different filler loadings of each silica and rice husk separately (2,4 and 6wt%). It is perceived that with the increase in the rice husk filler loading in epoxy, there is a decline in tensile, flexural, and erosion wear properties. It is also evident that, with the increase in silica content until 6 %, the tensile and flexural strength have displayed consistent enhancement. Alongside, erosion results confirm that the properties of the pure epoxy had exhibited transition from semi-brittle to ductile nature due to the addition of silica fillers.

An Investigation of Tensile and Thermal Properties of Epoxy Polymer Modified by Activated Carbon Particle

In this work, the effects of adding activated carbon (AC) powder with epoxy resin were investigated experimentally. The particulate epoxy composites are manufactured in vacuum technique with different weight fraction ratios of AC (0, 5, 10, 15, 20, 25, 30, 35 and 40) % wt. The particle size was measured during this work by laser particle size analyzer with an average size of about (14.74μm). The interaction between epoxy material and AC powder was examined by using Fourier Transform Infrared (FTIR) spectroscopy analysis. Moreover, the glass transition temperature (Tg) of the pure epoxy and composite material were measured by Differential Scanning Calorimeter (DSC). The tensile strength behavior and interaction strength between the matrix material and powder were investigated by conducting tensile test and SEM analysis. The results of FTIR test reveal that there is no a new peak after reinforcing epoxy with AC powder, which proves there is a strong interaction between epoxy resin and AC powder. The DSC results show that the increases by adding AC to epoxy will increase Tg temperature. The findings of FTIR analysis were supported by SEM analysis, which shows a good interaction and strong interfacial between matrix and particles. The tensile strength values increased with increasing AC content up to 15 % wt. with a max value of 26.34 MPa (19.16%), then it decreased to 18.15 MPa at 40 % wt.

Textured Orientation and Dynamic Magnetoelastic Properties of Epoxy-Based TbxDy0.7–xPr0.3(Fe0.9B0.1)1.93 Particulate Composites

The texture-oriented TbxDy0.7−xPr0.3(Fe0.9B0.1)1.93/epoxy particulate composites are fabricated with a magnetic field of 640 kA/m. The -oriented 1–3 type (x ≤ 0.16) and -oriented composites (x ≥ 0.22) are obtained. The composite exhibits a negative ΔE effect of elastic modulus (E3) with trivial eddy-current losses at frequency up to 50 kHz. The 1–3 type composite with a particle volume fraction Vf ~ 0.30 displays an enhanced magnetoelastic performance, that is, the dynamic piezomagnetic coefficient d33 ~ 2.2 nm/A at Hbias ~ 80 kA/m, which is 150% higher than that of its 0–3 type one and approaches 92% of its monolithic polycrystalline alloy. This enhanced effect can be attributed to its easy magnetization direction (EMD) lying towards axis as well as the formation of -texture-oriented structure. This facile approach will open a new way to prepare magnetoelastic composites for high-frequency applications.

The interaction between encapsulated Gd2O3 particles and polymeric matrix: The mechanism of fracture and X-ray attenuation properties

This work sheds light on the relationship between the quantities of synthesized core shell Gd2O3 added to epoxy matrix and the mechanical and X-ray attenuation properties of particulate epoxy composite. Then, an optimal geometric design of non-lead based X-ray protective material with light weight per volume unit is prepared. A plateau with 28–30% increments in the value of fracture toughness (KIC) is observed with a specific addition of 0.08–0.1 volume fraction (φS) of Gd2O3 particles in pure epoxy. The same quantity of particles also optimally raises the critical strain energy release rate and Young’s modulus of epoxy by approximately 22–24% and 18–25% respectively. A 16mm thick sheet of fabricated filled composite at (φS) of 0.08 and 0.1 can shield greater than 95% and 99% respectively of a primary X-ray beam in the range of 60–120kVp. At the same X-ray attenuation (99% attenuation), the specimen is 7, 8.5 and 16 times lighter than wood, glass, and concrete, respectively. At 0.5mm Pb-equivalence, the composite also has 4.5–19.4% less weight per unit area than current commercial non-lead products.

Moisture Absorption Behavior of Treated and Untreated Eggshell Particulate Epoxy Composites

Weight gain and thickness swelling in bio-waste composites material leads to an adverse effect on properties. In the present investigation the effect of different environments (saline, mineral, kerosene, subzero temperature) on the physical properties of the composites which are fabricated with unboiled(untreated) and boiled(treated 200 °C) eggshell filler materials are studied. XRD, SEM and ultimate analysis of the unboiled and boiled eggshells are also studied. The composites of different weight percentage 4, 8 and 12 wt% of unboiled and boiled eggshell filler epoxy composites are fabricated by a hand lay-up technique. The 12 wt% of boiled eggshell particulates reinforced epoxy composites showed the highest weight gains when exposed to different environments. Least absorption rate observed was for 4 wt% eggshell filler composite in subzero temperature condition. The composites showed a peculiar environmental behavior when exposed to kerosene.

Influence of particle contiguity and interphase on the stiffness of particulate epoxy composites

A theoretical model for the evaluation of the elastic modulus in particulate composites has been developed. The method takes into account the contiguity of the particles and also the existence of an interphase between main phases, which constitutes an important parameter influencing the behavior of a composite material. This layer between the matrix and filler develops different physico-chemical properties from those of the constituent phases and variables along its thickness. The effect of the progressive variation of the elastic modulus of the interphase on the modulus of the composite was estimated by assuming a law of variation. The theoretical values derived from the proposed model were compared with experimental results carried out on iron-particulate-filled epoxy composites and with theoretical values derived from models of other scientists. This comparison was proved to be satisfactory for our proposed model.

Effects of Environmental Conditions on Erosion Wear of Eggshell Particulate Epoxy Composites

The erosion wear behaviors of unboiled (UB) and boiled eggshells filler reinforced epoxy composites have been characterized. The eggshells epoxy composites have been fabricated using a hand layup technique and the samples have been exposed to different environmental conditions i.e. dry, saline, mineral, kerosene and subzero temperature. To examine the effect of the above mentioned environmental conditions at different impingement angles (30, 45, 60, and 90∘) three different particle velocities (v = 86 m/s, 101 m/s and 119 m/s) were selected for the erosion wear behavior. The highest erosion rate is found at 60∘ impingement angle, which indicates the semi-brittle erosion nature of eggshells epoxy composites. The impingement angle and impact velocity have a notable influence on erosion rate. A fruitful effect of filler addition is observed on the erosion wear rate of composites. The erosion rates of unboiled and boiled eggshells epoxy are compared. The 4 wt% unboiled eggshells filler content shows the highest wear resistance in dry condition. The exposure of composites in different environmental conditions had a negative effect on erosion rate.

Effects of environmental exposure on tribological properties of Arhar particulate/epoxy composites

The solid particle erosion behavior of Arhar particulate epoxy composites with 5, 10, and 15 wt% particulate content has been characterized. The Arhar particulate epoxy composites have been fabricated using hand lay‐up technique, and samples have been exposed to different environmental conditions, such as dry, saline, mineral water, kerosene, and subzero, before erosion test. The effect of different environments on erosion wear rate is investigated for all the composites. The rate of erosion at which Arhar particulate epoxy composites undergo when subjected to various impingement angles (30, 45, 60, and 90°) and at particle speeds (v = 86, 101, and 119 m/s) using air jet erosion test rig has been evaluated. Erosion behavior of Arhar particulate composites is found to be less when compared with neat epoxy material. Normal samples showed semibrittle erosive behavior. Erosive wear rate is more in samples with 15 wt% particulate content. Erosion wear is higher in samples immersed in saline water. Erosive wear behavior samples immersed in saline water, mineral water, and kerosene, which is found to be semibrittle. POLYM. COMPOS., 39:3102–3109, 2018. © 2017 Society of Plastics Engineers

Exploring the piezoelectric performance of PZT particulate-epoxy composites loaded in shear

The active and passive piezoelectric response of lead zirconium titanate (PZT)-epoxy particulate composites loaded in shear is studied using analytical models, a finite element model and by experiments. The response is compared to that of the same composites when loaded in simple tension. Analogously to bulk PZT, particulate PZT-polymer composites loaded in shear show higher piezoelectric charge coefficient (d15) and energy density figure of merit (FOM15) values compared to simple tension (d33) and (FOM33). This outcome demonstrates the as-yet barely explored potential of piezoelectric particulate composites for optimal strain energy harvesting when activated in shear.

The Stiffness and Thermal Expansion Coefficient of Iron Particulate Epoxy Composites Defined by Considering the Particle Contiguity

A theoretical model for the determination of the stiffness and the thermal expansion coefficient of particulate composites is presented in this work. This model takes into consideration the influence of neighboring spherical particles on the thermo mechanical constants of the composite material consisting of matrix and filler. A microstructural composite model which represents the basic cell of the composite at a microscopic scale was transformed to a tetraphase spherical representative volume element, (R. V. E.), in order that classical theory of linear elasticity is applied. This work constitutes a modified consideration of body – centered tetrahedral models that appeared in the literature. The obtained theoretical results using this model were compared with experimental results carried out on iron particles reinforced epoxy resin composites as well as with other theoretical values derived from well known expressions given in the literature and derived by other scientists. Finally an observation of the fracture surface of the specimens was performed through S. E. Microscopy.

Effect of external loads on damage detection of rubber‐toughened nanocomposites using carbon nanotubes sensory network

Multiwalled carbon nanotubes of 0.2% weight fraction are used as a sensory network for detecting and characterizing the damage of particulate epoxy composites under shear loading conditions. Three different weight fractions of carboxyl‐terminated butadiene acrylonitrile copolymer rubber [10 parts per hundred of epoxy resin (phr), 20 phr, and 30 phr] are used for toughening a thermoset epoxy composite. The electrical response of the specimens is measured, nearest the central shearing plane, using a four‐circumferential ring probe technique in conjunction with a high‐resolution data acquisition system. A collection of the electromechanical response results are reported with respect to the shear strain. The resistance changes observed under shear loading are related to nonlinear deformation mechanisms, void initiation, and growth around rubber particulate. With increasing rubber content, the strength of the material decreases and a greater drop in resistance is recorded as a result of decreased distance between neighboring carbon nanotubes (CNTs) due to declustering and straightening of molecular chains of host matrix. In the end, a comparison for 30 phr composites under shear loading with that of tensile and compression loading conditions is presented. For initial deformation, there is no change in resistance under shear loading condition; however, the significant resistance change can be noticed under both tension and compression. The specimen under shear loading conditions experiences smaller decrease in resistance when compared with both tension and compression. However, the decrease in resistance is higher for compression due to higher decrease in distance between neighboring CNTs. POLYM. COMPOS., 37:360–369, 2016. © 2014 Society of Plastics Engineers

Damage detection of rubber toughened nanocomposites in the fracture process zone using carbon nanotubes

A detailed experimental study is conducted using multi-walled carbon nanotubes (MWCNTs) as a sensory network to understand damage initiation and growth within the process zone of epoxy particulate composites under opening mode fracture loading. Thermoset epoxy resin composites are toughened with three weight fractions of carboxyl-terminated butadiene acrylonitrile copolymer (CTBN) rubber (10phr, 20phr and 30phr). Single-edge notch tension (SENT) geometry and far-field tensile loading conditions are used for this study. A modified four-point probe methodology coupled with a high-resolution data acquisition system is employed to capture the electrical response within the process zone of fracture test specimens. For each composite, the damage initiation and growth associated with linear and non-linear deformation is analyzed and discussed with respect to the change in crack tip opening displacement (CTOD). Although the electrical response did not differ qualitatively with the addition of both 10phr and 20phr rubber to epoxy, addition of 30phr of rubber showed a significantly different response both qualitatively and quantitatively. This is the result of several mechanisms such as disentanglement and stretching of epoxy matrix molecules, micro-crack blunting, debonding of rubber particles, void growth and propagation.

In situ sensing of non-linear deformation and damage in epoxy particulate composites

Damage sensing of epoxy particulate composites was investigated using multi-wall carbon nanotubes (MWCNTs) under quasi-static uniaxial tensile loading. Two types of particulates, namely (a) aluminum silicate hollow microspheres (cenospheres), and (b) liquid carboxyl-terminated butadiene acrylonitrile (CTBN) rubber were considered in this study. The influence of three different volume fractions of cenospheres (10%, 20% and 30%) and three different weight fractions of CTBN resin (10, 20 and 30 phr) on the electromechanical response was studied. A four-circumferential ring probe (FCRP) technique was employed to measure the electrical resistance of the test specimen as a function of the axial strain. The resistance–strain curve is compared with a simultaneously measured mechanical stress–strain curve. The electromechanical measurement show additional stages of material deformation not readily revealed from the mechanical stress–strain curve. The resistance change associated with the unfolding of entangled polymer chains and further straightening of the polymer chains decreased the distance between CNTs, causing improved electron hopping in all composites except 30% cenospheres composite. The U-shaped electrical response demonstrated by both 20 and 30 phr rubber composites exploited the CNT sensory network successfully by providing early warning of composite failure due to micro-crack propagation which resulted in breaking of the CNT network.

Measurement of the Young's modulus in particulate epoxy composites using the impulse excitation technique

A study of the Young's modulus as a function of the volumetric filler content in an epoxy matrix was carried out. To this aim, composites were prepared adding to the resin matrix particles of aluminum, copper and quartz with typical sizes of about 100μm. To measure values of the Young's modulus, an experimental set-up based on the impulse excitation technique was developed. The results obtained are discussed in terms of two well-known micromechanical models: one based on the Hashin–Shtrikman relationships and in the other one the Kerner equation was used. The analysis of the information obtained for the three different types of filler used allow concluding that the Kerner equation describes correctly the Young's modulus behaviour as a function of filler content. From the fitting procedure of the experimental data, additional information regarding the Young's modulus was obtained.

Interphase modeling of copper‐epoxy particulate composites subjected to static and dynamic loading

AbstractIn this investigation, the static and dynamic behavior of copper‐filled epoxy particulate composites has been experimentally studied. The influence of particle‐weight fraction (0–25%), on the static behavior and filler concentration, temperature and frequency on the dynamic behavior of the mentioned particulate composites was thoroughly studied. Experimental results for the static three‐point bending modulus were compared with respective theoretical predictions derived from that existing in literature semiempirical models. Results were also compared with predictions derived by the application of the interphase model previously developed by the first author for the evaluation of the elastic modulus in particulate composites, taking into account the effect of filler‐matrix adhesion. It was found that the predicted values as derived from the application of the interphase model were in better agreement with experimental findings when compared with respective predictions derived from other models. Polymer‐filler degree of adhesion was also studied by applying the Turcsànyi model. Extended SEM investigations and DMA tests were also made to support both experimental and theoretical findings. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

The equation of state of two alumina-filled epoxy resins

The shock Hugoniots of two different alumina–epoxy particulate composites have been measured in terms of shock velocity, particle velocity and shock stress. Both shock velocities and shock stresses increase with increasing amounts of alumina loading. The shock velocity–particle velocity relationships have been shown to be linear, and that with increasing alumina, behaviour shifts from a viscous to a response more commonly seen in metals and ceramics. Comparisons of the calculated hydrodynamic pressure and shock stress suggest that these materials have a constant shear strength with increasing shock stress. Finally, comparison of the material with the highest amount of alumina, with the work of others, shows close agreement.

Influence of low filler content on some thermomechanical properties of particulate epoxy composites simulated by a variant tetra-phase model

The influence of low filler content on some thermomechanical properties of particulate composites was determined. A variant of a previously developed theoretical model valid for low filler contents was used to evaluate the elastic modulus and thermal expansion coefficient of a particulate composite. In the experiments, filler volume fractions of 3, 5, 7 and 10% were used. The density and the velocity of longitudinal waves in these iron particle epoxy resin composites were also determined. An attempt has been made to explain qualitatively some of the discrepancies observed between theoretical models and experimental data. This approach was in part assisted by scanning electron microscopy observation of structural inhomogeneities and fractographic data. The theoretical values derived from the present model agreed satisfactorily with the experimental results and with theoretical values of other workers.

Analysis of Weight Change in Fly Ash – Epoxy Particulate Composites Immersed under Hot Water

Weight changes in epoxy filled with low-cost abundantly available filler, fly ash subjected to immersion in water maintained at an elevated temperature are studied. The effect of volume fraction of the filler on the water absorption characteristics is analysed. The extent and possible modes of water transport in the matrix and in the filler or filler-matrix interface are inferred through the study of absorption data. An attempt to explain this movement through the percolation model is made and support for the inferences arrived at is sought from microscopic observation using Scanning Electron Microscope.