Carbon Reinforced Polymer Composites Research Articles

Post lightning strike residual compressive strength prediction in unidirectional carbon reinforced polymer composites

Post lightning strike residual compressive strength prediction in unidirectional carbon reinforced polymer composites

Multi-attribute optimization of drilling CFRP/Ti-6Al-4V alloy hybrid stacks using VIKOR

Drilling carbon reinforced polymer composites (carbon fiber-reinforced polymers, CFRP) and the hole quality produced are highly critical and significantly influence the performance and reliability of structures used in aircraft components. When CFRP composites are stacked together with titanium alloy, the damage caused by the machining operation is incalculable due to the burr and chip evacuation of metallic phases. In this article, efforts were made toward the identification of optimal machining conditions in drilling CFRP/titanium hybrid stacks. Experimental investigations on dry drilling of CFRP/titanium stacks were conducted with the aid of tungsten carbide drills. This research article discusses an improved compromise ranking method named VIKOR (VIseKriterijumska Optimizacija I Kompromisno Resenje) to determine the optimal machining parameters in drilling of CFRP/titanium stacks to produce high-quality holes. Attributes measured from experimental trials are: delamination factor of CFRP, burr height of titanium alloy, thrust force, torque, surface roughness, roundness and hole diameter of CFRP and titanium alloy. Experimental trial 13 with a combination of speed of 30 m/min, feed of 0.025 mm/rev was chosen as an ideal machining parameter in drilling CFRP/Ti-6Al-4V stacks without any trade-off. Confirmation tests convey that the results agree well with optimal parameters and the decision making in drilling such multimaterial stacks is highly consistent and judicious. In regard to the optimal parameters determined, investigations on tool life were performed and a tool life of 20 min for 0.10 mm flank wear land was observed.

A Novel Method to Quantify Self-Healing Capabilities of Fiber-Reinforced Polymers

The present work investigates a novel and practical method to evaluate the healing efficiency of carbon-reinforced polymer composites. The method should be representative of damage occurring during the lifetime of a composite part, should tend to damage the healable matrix mostly and yet be simple and cost-effective to set up. Thus, the capacity to recover low-velocity impact damage has been evaluated via three-point bending flexural tests. Carbon-reinforced composite laminates were produced using HealTech™ T300-TW200-42RW-1250, a commercial healable resin pre-impregnated Torayca T300 3K twill 2 × 2 fabric with an aerial weight of 200 g/m2. Fibers were oriented at ± 45° or at 0°–90°, and the laminates were impacted at different energy levels. Flexural properties of undamaged, damaged, and healed samples were compared, and the healing efficiency was calculated as the ratio of healed and undamaged ultimate flexural strength or modulus. Since matrix healing efficiency is the value to characterize, it was shown that ±45° laminates could be tested without major fiber damage and, thus, provide the best matrix healing efficiency results. Such a method proved to be 1) representative of early-stage damage of composite FRPs often occurring in the form of delamination or matrix microcracking, and 2) a fast and reliable characterization technique requiring the use of a limited amount of material.

Influence of Carbon Micro- and Nano-Fillers on the Viscoelastic Properties of Polyethylene Terephthalate.

In this research study, three carbon fillers of varying dimensionality in the form of graphite (3D), graphite nano-platelets (2D), and multiwall carbon nanotubes (1D) were incorporated into a matrix of poly (ethylene terephthalate), forming carbon-reinforced polymer composites. Melt compounding was followed by compression moulding and then a quenching process for some of the samples to inhibit crystallization. The samples were analysed using dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM), considering the dimensionality and loading of the carbon fillers. The dynamic mechanical analysis revealed a similar decline of storage moduli for all composites during the glassy to rubbery transition. However, storage moduli values at room temperature increased with higher loading of nano-fillers but only to a certain level; followed by a reduction attributed to the formation of agglomerates of nanotubes and/or rolled up of nano-platelets, as observed by SEM. Much greater reinforcement was observed for the carbon nanotubes compared to the graphite and or the graphite nano-platelets. The quenched PET samples showed significant changes in their dynamic mechanical properties due to both filler addition and to cold crystallization during the DMTA heating cycle. The magnitude of changes due to filler dimensionality was found to follow the order: 1D > 2D > 3D, this carbon filler with lower dimensionality have a more significant effect on the viscoelastic properties of polymer composite materials.

Interphase approach for modeling the DC conductivity of diverse allotropic types of carbon-reinforced polymer composites

This work is based on a generalized effective medium-modified model for predicting the DC electrical conductivity of polymer composites, taken into account the interactions between the components using an interphase approach. Generalized effective medium-modified model is a simple extension of the Generalized Effective Medium Theory proposed by McLachlan. We studied the modeling of the DC electrical conductivity using the proposed model for diverse allotropic types of carbon-reinforced polymer composites. Three series of composite materials obtained by mixing an insulating matrix DGEBA with (i) carbon nanotubes which are one-dimensional materials (1 D), (ii) reduced graphene oxide, which is a two-dimensional material (2 D) and (iii) carbon black, which is a three-dimensional material (3 D) have been studied. Predictions from the model are in good agreement with the experimental data of the electrical conductivity of composite materials, where the classical models have not been able to explain them. Moreover, in this paper, the effects of the filler dimension on the interphase properties of the composite materials, in particular the interphase volume fraction and the interphase conductivity, have been investigated.

Validation of trace-based approach to elastic properties of multidirectional glass fibre reinforced composites

A recent invariant-based theory of composites is re-examined using multidirectional laminates through classical lamination theory applied on experimental data and micromechanical predictions for unidirectional laminates. Initially, the master ply values developed for carbon reinforced polymer composites (CFRP) proved to be inappropriate for aramid and glass reinforced polymer composites (KFRP and GFRP). This led to part the material systems into four classes, According to the type of reinforcing fibre, with dedicated master ply values. By then, GFRP was declared unfit for this theory due to the wide variation of the trace-normalized stiffness parameter with a small variation of longitudinal modulus. Here, the specialization of master ply values for KFRP and GFRP is demonstrated using micromechanical predictions. The invariant-based theory is applied to short beam deflection of multidirectional laminates and cross-ply GFRP laminates. This approach leads to small errors, for all material classes including GFRP. In brief, GFRP composites proved fit for invariant-based theory under the present conditions.

Fracture toughness enhancement of carbon fiber–reinforced polymer composites utilizing additive manufacturing fabrication

The present work reports a novel approach to enhance the fracture resistance and notch sensitivity of carbon fiber-reinforced polymer composites utilizing additive manufacturing (3-D printing) fabrication. The 3-D printed composites utilize carbon fiber bundles to reinforce nylon/chopped fiber resin in a multilayered structure configuration. Single-edge (60°) notched samples were printed using Mark Two printer. Three reinforcement schemes were designed and used to manufacture the specimens. The focus was placed on selective reinforcement at the crack tip to arrest crack initiation. The mechanical properties, fracture toughness, and fracture behavior of the printed composites were evaluated. It was found that wrapping fiber around the notch effectively blunted the notch and redirected crack propagation away from the notch tip, thereby lengthening the crack path and leading to improved fracture resistance. It was also found that such improvement reaches a saturation level. Excessive notch reinforcement beyond optimal limit can reverse the gains in fracture resistance due to notch-targeted reinforcement. Examination of the fracture surface morphology of the printed composites reveals lack of fusion of the sizing of the individual continuous carbon fiber bundles and the lack of adhesion between the matrix layers (nylon/chopped fiber resin) and the adjacent carbon fiber bundle reinforcement. Damage to the fibers within the carbon bundle was also observed. Thus, a synergetic effect of the carbon fiber bundles reinforcement and the matrix requires more optimization to manufacture carbon-reinforced polymer composites using 3-D printing.

Analytical model for predicting the tensile strength of unidirectional composites based on the density of fiber breaks

Abstract While analytical fiber fragmentation models following the global load-sharing (GLS) assumption efficiently reproduce the stress strain curves of unidirectional composites loaded in the direction of the reinforcement when the number of breaks is moderate, they completely fail to predict tensile strength. In this paper, we propose that failure takes place when a critical density of breaks, which depends entirely on the constituent properties, is reached. Therefore, we rewrite classic GLS fragmentation models in terms of the linear density of breaks. The critical number of breaks for a set of glass and carbon reinforced polymer composites is extracted from published experimental data and fitted to an empirical law, with good predictive capability. Our approach complements GLS fragmentation models because it identifies the ultimate stress, from which the stress-strain curve given by the model becomes unrealistic.

Prediction of filler/matrix interphase effects on AC and DC electrical properties of carbon reinforced polymer composites

This study predicts the effect of the conducting filler/insulating matrix interphase on the electrical properties of two series of percolated systems, differing from the type of carbon black particles mixed in an amine‐cured epoxy matrix, diglycidylic ether of bisphenol F. To take into account the interactions between the conducting filler and the matrix, as well as filler–filler overlapping, we introduce three parameters, characteristic of the interphase zone, such as concentration, conductivity and volume, on the generalized effective medium (GEM) model for DC and AC electrical conductivities. These interphase parameters, characterizing the boundary of the shaded zone between the macromolecular chain and the conducting particles, depend on the filler type and concentration. One output of GEM‐modified model is that it provides a mean to estimate the volume, concentration and intrinsic conductivity of the interphase in a composite by fitting the experimental data over a broad range of frequency. POLYM. COMPOS., 40:346–352, 2019. © 2017 Society of Plastics Engineers

Influence of chemical treatments on mechanical properties of hemp fiber reinforced composites

Abstract Natural Fibers Reinforced Composites (NFRC) are finding much interest as a substitute for glass or carbon reinforced polymer composites, like for instance automobile interior linings (roof, rear wall, side panel lining), shipping pallets, construction products (i.e. composite roof tiles), furniture and household products (i.e. storage containers, window and picture frames as well as food service trays, toys and flower pots) as well as fan houses and blades. However, a notable disadvantage of lignocellulosic fibers as reinforcements is their polarity which makes it incompatible with hydrophobic thermoplastic matrix. This incompatibility results in poor interfacial bonding between the fibers and the matrix. This in turn leads to impaired mechanical properties of the composites. This defect can be remedied by chemical modification of fibers so as to make it less hydrophilic. In this paper experiments have been performed to further the development of natural fiber reinforced composites. Untreated and treated surfaces of hemp fibers were characterized using Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM). Fiber-matrix adhesion was promoted by fiber surface modifications using an alkaline treatment and (3-Glycidyloxypropyl) trimethoxysilane coupling agent. The mechanical behaviour of epoxy matrix composite reinforced with woven hemp was studied and mechanical test results show that silane treatment of hemp fibers improves, both tensile and flexural properties of the composites, although no high values are obtained.

Assessment of Elasticity Characteristics and Strength Parameters of Unidirectional Polymer Composites at High Temperatures

Within the framework of transversally isotropic body, the possibilities of describing the elasticity characteristics and load-bearing capacity of unidirectional carbon-reinforced polymer composites at high temperatures are analyzed. The dependences of the elasticity characteristics and strength parameters of the composite on the heating temperature and rate are established. The models for calculation of strength characteristics of ablating composite in cases of tensile or compressive loads codirected with the reinforcement axis are developed and discussed.

Structural design and functional bionic of nano carbon composites

With unique structure and excellent properties, nano carbon composites like carbon nanotube (CNT) and graphene (GE), have become research focus in nano technology and nano materials, and promoted the rapid development of multifunctional nanocomposites since their discovery. However, with traditional preparation method, the volume of nanometer carbon content in composite materials can only reach 5%–10% due to nanoparticles aggregation and rheological properties of resin, etc. Different from a small amount of nano carbon reinforced polymer composites, nano carbon composites with high concentrations can better exhibit the properties of nano materials, with more advantages in stress transfer, higher shear and tensile breaking strength, have attracted more and more attention in research and applications for these years. With the development of new nano carbon composite materials, more requirements about the structure design and functional development of materials were put forward. The structure of nano carbon units and their arrangement, uniform dispersion and interfacial interaction are extremely important to performances of composite materials. Traditional way can optimize orientation degree and improve packing density but it is still not enough, such as stretching can effectively improve the mechanical and electrical properties of materials, but cannot fundamentally solve the aggregation phenomenon of nanometer unit, performance of conversion efficiency in nano unit is still low. Fortunately, the nature provided us a new clue on the design of high performance and multifunctionalities of nano carbon materials. Structure and interface bonding composites in the organism are both strong and tough. Therefore, nano carbon composite materials of bionic structure are one of the important development directions in the future, and have got the attention of the researchers. In addition, the bionic structure and interface on the energy conversion phenomena, can also realize the function of the composite material bionic, making the nano carbon composite materials have perception, adaptive, self-driven bionic multi-functional characteristics, etc. First, based on traditional processing methods, we obtained the further optimization of carbon nanotubes orientation degree through bionic processing, with good control of aggregation in high volume content of carbon nanotube composites. Second, the rich interface bonding mechanism in laminated shell structure was found, and a hard and soft material with a certain strength and toughness was prepared. Third, on the basis of functional bionics, more abundant sensing and response forms of the smart drive, stronger response ability, more expansive functional applications were achieved. Therefore, learning from the nature, rationalization of structure, excellent performances, controllability and highly efficient applications of which have been achieved by structural design and integration of ideas. And this biomimic method has become an important direction of nano composites. While we still have many things to do in nano carbon composite materials with this approach and lack a deep understanding of the transformation mechanism between biological structure and function. In this paper, we have reviewed the preparation and processing of high content nano carbon composites and their bionic design of structure and interface. Also the progress in applications of bionic smart drive was introduced. In the end, we discussed the development direction of multifunctional nano carbon composites.

FABRICATION AND EVALUATION OF NANO CARBON REINFORCED POLYMER COMPOSITES

In this study the suitability of using nano carbon as a new raw material for thermoset composites is investigated. The study evaluates the mechanical properties of nano carbon composites. The nano carbon from Biomass (waste material of Zea Mays) is used as a reinforcement material with the matrix resin for preparing the composites. The composites developed by hand molding technique are varied with weight percentage of nano carbon (0.1%, 0.2%, 0.3%, and 0.4% up to 1.5%). The developed natural nano carbon reinforced polymer composites were characterized by mechanical properties. The composites reinforced with 0.5 & 0.6 wt% of nano carbon particles have shown better mechanical strength. The properties of sourghum based nano carbon/Epoxy composites are greater than that of epoxy resin matrix composites even for a little amount of carbon reinforcement.

Ablation behaviors of carbon reinforced polymer composites by laser of different operation modes

Laser ablation mechanism of Carbon Fiber Reinforced Polymer (CFRP) composite is of critical meaning for the laser machining process. The ablation behaviors are investigated on the CFRP laminates subject to continuous wave, long duration pulsed wave and short duration pulsed wave lasers. Distinctive ablation phenomena have been observed and the effects of laser operation modes are discussed. The typical temperature patterns resulted from laser irradiation are computed by finite element analysis and thereby the different ablation mechanisms are interpreted.

Investigation of the Electro-Discharge Open-Hole Machining on the Structural Behavior of Carbon Fiber Reinforced Polymers

The current work investigates the electro-discharge machining (EDM) of plain woven carbon reinforced polymer composites with pulse durations of 100 μs, 200 μs, 300 μs, currents 1 A, 3 A and 5 A, and a voltage of 100 V. An x-ray computed tomography (CT) is employed to examine the delaminations, while a delamination factor model utilizing the equivalent delamination diameter provides the measuring quantity for assessment. Finite element simulations compute the stress concentrations around the holes by taking into account the delamination equivalent diameters of the open-holes, as monitored from the x-ray CT. The Whitney-Nuismer point stress criterion is utilised in order to predict the failure strength of the machined open-hole laminates and it is compared with the experimentally derived mechanical strength values. The results reveal that EDM is a feasible method for open-hole machining of composites, however proper selection of the operational parameters is needed. By accurately measuring the peripheral delamination areas of the machined holes, it is shown that the analysis of the mechanical behaviour of the plain woven laminates by the means of finite element method and the Whitney-Nuismer criterion can accurately predict the response of such composites when subjected to tensile loads.

Effects of fibre orientation and content on the mechanical, dynamic mechanical and thermal expansion properties of multi-layered glass/carbon fibre-reinforced polymer composites

Multi-layered glass and carbon-reinforced polymer composites may exhibit unique properties comparatively with the benchmark, proven they are being tailored bounded by several requirements. The paper herein approaches issues on the influence of the various contents and orientation of UD carbon fibre constitutive on the mechanical, dynamical and thermal expansion if embedded along with glass fibres in different stacking sequencing within an unsaturated polymer resin. The results show that the architectures with the highest content of carbon fibres (e.g. GF:CF(60:40) – 0° and 90°) provide the best tensile and flexural properties, and behave better under dynamical loading conditions and temperature variations, no matter the orientation directions. In addition, it was shown that a thorough understanding can be attained, with respect to the UD carbon fibre content, and different orientations influence on the overall composite material properties, taking into account the data retrieved from dynamical and thermal expansion runs.

Seismic Response Analysis of CFRP Retrofitted Reinforced Concrete Structures

The use of carbon reinforced polymer (CFRP) to provide lateral confinement for enhanced ductility and strength of reinforced concrete structures has been increasing. The present study, attempts to analytically investigate the effect of the layout of frame columns retrofitted with different layers of CFRP on the seismic performance and damage potential of structures under strong ground motion using realistic and efficient computational models. Based on the shaking table tests of several reinforced concrete (RC) flat slab beamless construction models, the seismic performance of structures strengthened with CFRP composites are investigated. The dynamic response of CFRP retrofitted structures and the components of the model, validation of the model, force-displacement relationship, relative displacement and the time history curves are studied. Then the rational effect of different CFRP layers is found.

Stress-dependent piezoresistivity of tunneling-percolation systems

We studied the stress-dependent piezoresistive behavior of tunneling-percolation systems. Starting from percolation-like power law of resistivity, a model relating piezoresistive stress coefficient to the applied stress has been developed by considering the stress-induced changes in the critical exponent and that in the concentration of conducting phases. It is found that the coefficient exhibits reverse and logarithmic dependence on the applied stress in the different stress ranges. We show that the experimental data, obtained from carbon-reinforced polymer composites and polymer-derived ceramics, follow the theoretical prediction of the model very well, indicating that the stress effects described by the model indeed exist in tunneling-percolation systems.

Trends in composite materials: the challenge of single-polymer composites

vation and energy saving may come from our ability to recover, recycle and/or reuse the materials. Consumer consciousness, waste management regulations and environmental legislation are all pushing the manufacturers of raw-materials and end-products to carefully consider the environmental impact of their products at all stages of the life cycle, including ultimate disposal. This scenario obviously involves also composite materials, increasingly used in several industrial sectors. In fact, there is a marked interest to improve the methods for recycling and reusing the existing composites, or to develop new ones intrinsically more suitable to be recycled and reused. In this framework, a great deal of efforts has been expended for the development of the so called ‘single-polymer’ composite (SPC) materials, in which both the reinforcing and the continuous phases are polymers with the same chemical composition. These materials have been also denoted as onepolymer composites, homocomposites, all-(the same) polymer composites, or homogeneity composites. The main advantage of SPCs is that, unlike traditional heterogeneous composites (such as glassor carbon reinforced polymer composites), they can be entirely melted down at the end of the product life for recycling. The first example of this kind of composites was reported by Capiati and Porter in 1975, who introduced the concept of single-polymer composites by successfully preparing polyethylene/polyethylene composites. More recently, the preparation of polypropylene, poly(ethylene-terephthalate), poly(ethylene-naphthalate), and liquid-crystalline copolyesters single-polymer composites has been extensively studied. In most cases, SPCs have been obtained through the so called ‘hot compaction’ technique. The use of temperature and pressure to control the melting of the outer surface layer of polymeric fibres implies that the processing window for the hotcompaction process is quite narrow. Other processing techniques include film or fibres stacking, powder impregnation, solution impregnation, etc. An intriguing challenge for materials scientists and engineers is to explore new materials combinations to extend the processing window and to develop processing techniques sufficiently versatile to be scaled up at an industrial level.

Non-Metallic Composite Materials for Bone Surgery

Possibility of using non-metallic materials in biomedical applications was considered. The attention was focused mainly on polymer materials and both the carbon-carbon and carbon-reinforced polymer composites, their mechanical and biological properties. The obtained results indicate that some of these materials can be successfully used instead of metallic implants for biomechanical functions.