Fiber Polymer Composites Research Articles

Modelling and Analysis of the Mechanical Properties of Agave Sisalana Variegata Fibre / Vinyl Ester Composites Using Box-Behnken Design of Response Surface Methodology

In this paper, the Box-Behnken (BB) experimental design of response surface methodology (RSM) was utilized to study the effect of process parameters on the mechanical properties of agave sisalana variegata (ASV) fibre-reinforced vinyl ester (FRVE) composites. The fibre length, fibre content, and fibre diameter were used as process parameters to develop a model using the BB experimental design. Experimental tests were carried out based on the BB design. The experimental tensile and flexural strength values were fitted with the predicted strength values by a second-order polynomial equation via a multiple regression analysis. The results show that the tensile and flexural strength can be predicted by the developed models with more than 98.54 % of the variation in the tensile strength and 99.24 % of the variation in the flexural strength. The level 3 of fibre length (13 mm), level 2 of fibre content (35.19 wt %), and level 1 of fibre diameter (0.24 mm) were selected as the optimal levels of fabrication process parameters using the response surface graph and models. Finally, it was proved that the BB design of response surface methodology could efficiently be applied to the modelling and optimization of the mechanical properties of natural fibre polymer composites.

Effect of fiber content and surface treatment on the mechanical properties of natural fiber composites produced by rotomolding

In this study, natural fibers (agave, coir, and pine) were surface treated with maleated polyethylene (MAPE) with two main objectives: (1) to improve the mechanical properties of natural fiber composites produced by rotational molding and (2) to increase the fiber content in the composite. The rotomolded composites were produced at 0, 10, 20, 30, and 40% wt. of fiber contents (treated or untreated) and characterized in terms of morphology and mechanical properties (hardness, impact, tension, and flexion). The results showed that MAPE surface treatment was more successful for agave and coir than for pine fibers due to their respective chemical composition. In general, surface treatment led to better fiber distribution and a more uniform composite morphology allowing the possibility to use higher fiber contents in rotational molding. At low fiber contents (10 and 20% wt.), the mechanical properties were improved using treated fiber composites (TFC) compared to the neat polymer and untreated fiber composites (UFC). Although the mechanical properties of TFC decreased at high fiber contents (30 and 40% wt.), they were substantially higher (about 160, 400, and 100% for impact, tensile, and flexural properties, respectively) than for UFC.

Surface Characterization of Carbon Fiber Polymer Composites and Aluminum Alloys After Laser Interference Structuring

The increasing use of carbon fiber-reinforced polymer matrix composites (CFPC) and aluminum alloys as lightweight materials in the automotive and aerospace industries demands enhanced surface preparation and control of surface morphology prior to joining. In this study, surfaces of both composite and aluminum were prepared for joining using an Nd:YAG laser in a two-beam interference setup, enabling the (1) structuring of the AL 5182 surface, (2) removal of the resin layer on top of carbon fibers, and (3) structuring of the carbon fibers. CFPC specimens of T700S carbon fiber, Prepreg—T83 epoxy, 5 ply thick, 0°/90° plaques were used. The effects of laser fluence, scanning speed, and number of shots-per-spot were investigated on the removal rate of the resin without an excessive damage of the fibers. Optical micrographs, 3D imaging, and scanning electron microscope imaging were used to study the effect of the laser processing on the surface morphology. It was found that an effective resin ablation and a low density of broken fibers for CFPC specimens was attained using laser fluences of 1–2 J/cm2 and number of 2–4 pulses per spot. A relatively large area of periodic line structures due to energy interference were formed on the aluminum surface at laser fluences of 12 J/cm2 and number of 4–6 pulses per spot.

Sustainable, Biobased Silicone with Layered Double Hydroxide Hybrid and Their Application in Natural-Fiber Reinforced Phenolic Composites with Enhanced Performance

With wide application of natural fibers in polymer composites, improvements in their flame retardancy, water absorption, and electrical resistance become an urgent need. To this end, 4.5 wt % of layered double hydroxide (LDH) is introduced into sisal fiber reinforced biobased silicone modified phenolic composites. The modified composites optimally shows 60% reduction in total heat release (20.2 MJ/m2) compared to the composites without LDH. In addition, the biobased silicone modifier TDS is incorporated into phenolic resins (SPF), to further reduce water absorption rate to 6 wt %, and increase volume electrical resistance up to 4.6 × 1016 Ω m. The SPF-SF-SDBSLDH exhibits a high impact strength of 4.2 kJ/m2, over 50% higher than the unmodified PF-SF composites. The SEM observations show that the SPF composites exhibit better interfacial interaction with sisal fiber than normal phenolic (PF) composites. All these flame retardant, impact strength and electrical resistance properties are compatible with the r...

MODELS FOR INTRALAMINAR DAMAGE AND FAILURE OF FIBER COMPOSITES - A REVIEW

In order to fully exploit the potential of structures made from fiber composites, designers need to know how damage occurs and develops and under what conditions the structure finally fails. Anisotropy and inhomogeneity cause a rather complex process of damage development which may be one reason for an exceptionally large number of existing models. This paper intends to provide an overview over those models and give some hints about current developments. As such it is an updated version of a recent publication [1]. The survey is limited to laminates from unidirectional layers out of straight continuous fiber polymer composites under quasi-static loading. Furthermore, focus is laid on intralaminar damage.Many failure models smear out the inhomogeneity between fibers and the matrix. Simply limiting each stress component separately can lead to surprisingly good results as documented in the first World-Wide Failure Exercise. Interpolation criteria consider mutual influence of normal and shear stresses, predominantly through a quadratic failure condition. Traditionally one distinguishes between interpolation criteria and physically based ones. As an important physical effect the difference between fiber failure and inter-fiber failure is considered. Furthermore, stress invariants are taken as a basis, increased shear strength under compression is accounted for, and characteristic failure modes are captured. Fibers and the matrix material are characterized by a large disparity in stiffness and strength. Micromechanical models consider this inhomogeneity but suffer from the difficulty to determine relevant material properties. Compressive strength in fiber direction has attracted special attention. However, the role of kink band formation, which is observed in the failure process, seems to be not yet fully understood.In summary it must be concluded that despite the tremendous effort which has been put into the model development the damage and failure simulation of fiber composites are not in a fully satisfying state. That is partly due to lack of accurate and reliable test results.

Study the effect of fiber loading and alkali treatment on the mechanical and water absorption properties of wheat straw fiber-reinforced epoxy composites

Abstract The aim of this research was to study the feasibility of using wheat straw fiber with epoxy resin for developing natural fiber-polymer composites. For this purpose, the epoxy resin was reinforced with 5, 10, 15, 20, and 25 wt.% of the wheat straw fiber with the help of the hand lay-up technique. Further, in order to improve the composite characteristic, wheat straw fibers were treated with three different concentrations of alkali (1%, 3%, and 5%). The mechanical and water absorption properties of the treated fiber composites were characterized and compared with those of untreated fiber-filled epoxy composites. It was observed that the mechanical properties and water resistance were reduced with the increase in wheat straw fiber loading from 5 to 25 wt.%. Among the three levels of alkali treatment, the composite made with 3% alkali-treated fiber exhibited superior mechanical properties than the other untreated and treated fiber composites, which pointed to an efficient fiber-matrix adhesion. The scanning electron microscope was used to observe the surface features of the wheat straw fiber.

A Fiber Supercapacitor with High Energy Density Based on Hollow Graphene/Conducting Polymer Fiber Electrode.

A hollow graphene/conducting polymer composite fiber is created with high mechanical and electronic properties and used to fabricate novel fiber-shaped supercapacitors that display high energy densities and long life stability. The fiber supercapacitors can be woven into flexible powering textiles that are particularly promising for portable and wearable electronic devices.

Interfacial crystallization of isotactic polypropylene surrounding macroscopic carbon nanotube and graphene fibers

A comparative study on interfacial crystallization of isotactic polypropylene (iPP) surrounding macroscopic carbon nanotube and graphene fibers has been carried out in single fiber polymer composites by means of in situ polarized optical microscope, scanning electron microscope and X-ray diffraction. Ordered interfacial microstructures of iPP nucleate on both nanocarbon fibers in the form of a transcrystalline interphase. Nanotube fibers tend to promote negative birefringence transcrystals whereas graphene fibers induce positive birefringence transcrystals. The microstructures of transcrystals are strongly dependent on the thermal history and the double-layered transcrystals consisting of a negative inner layer and a positive outer layer occur under certain conditions. Transcrystallization kinetics has been studied and the Lauritzen–Hoffman theory of heterogeneous nucleation used to analyze the dynamic crystallization process. While the fold surface energy of iPP transcrystals surrounding both nanocarbon fibers shows little difference, the nanotube fiber promotes shorter induction time than the graphene fiber. Thermal resistance test demonstrates that the ordered interfacial microstructures possess higher melting temperature in the nanotube fiber composites than those in the graphene fiber composites. Under appropriate conditions, the β-form transcrystals of iPP are observed. The amount of the β-form iPP surrounding the nanotube fiber is much higher than that surrounding the graphene fiber. A theoretical model is proposed to interpret the difference between the nanotube and graphene fiber composites and the mechanisms behind its influence on interfacial crystallization.

Surface Modification of Natural Fibers for Reinforced Polymer Composites: A Critical Review

Recent advances in engineering, natural fibers development and composites science offer significant opportunities for new, improved materials which can be biodegradable and recyclable and can also be obtained from sustainable resources at the same time. The combination of bio-fibers like betel nut, banana, coir, jute, rice straw, tea dust and various grasses with polymer matrices from both non-renewable (petroleum based) and renewable resources to produce composite materials that are competitive with synthetic composites such as glass fiber reinforced polypropylene or epoxide has been getting increased attention over the last decades. This article provides a general overview of natural fibers and bio-composites as well as the research on and application of these materials. A special emphasis is placed on surface modification of natural fibers to attain desired composite properties. The roles of compatibilizers and radiation on the natural fiber-polymer composites are also included. A discussion about chemical nature, processing, testing and properties of natural fiber reinforced polymer composites completes this article.

Mechanical performance of CNT-filled glass fiber/epoxy composite in in-situ elevated temperature environments emphasizing the role of CNT content

Carbon nanotubes (CNTs) are one of the prime choice nano-filler reinforcement for fibrous polymeric composites. But the stability of the CNT/polymer interface is yet to be ensured for elevated temperature engineering applications. Present study deals with the assessment of elevated temperature durability of glass fiber/epoxy (GE) composite with various level of multi walled carbon nanotube (MWCNT) loading. Flexural testing at room temperature revealed that addition of 0.1% MWCNT yielded maximum strength (+32.8% over control GE) and modulus (+11.5% over control GE) amongst all the CNT modified composite systems. Further, MWCNT–GE composites resulted in accelerated degradation of mechanical performance with increasing temperature as compared to GE composite. Dynamic mechanical thermal analysis (DMTA) was carried out to study the viscoelastic behavior of all composites over a range of temperature. The design parameters were evaluated by Weibull probability function. Fractographic analysis figured out various failure modes in all composites at various temperatures.

Fracture Surface Morphology of Delamination Failure of Polymer Fiber Composites Under Different Failure Modes

The delamination of fiber reinforced polymer composites is one of the most common failures encountered in industrial applications. The most unique macroscopic and microscopic fracture surface features of the delaminations under different failure modes are of interests not only for practical failure analysis investigations but also it helps to reveal the physics behind the delamination phenomenon. In this work, fracture surface morphology of the delaminated carbon fiber polymer composites under mode I, mode II, and mixed-mode I/II loading conditions is investigated mainly with scanning electron microscopy. The unique fractographic features are identified and discussed. The results on ductile and brittle matrix composites have shown their own features, and most important of all the alignment angle of fibrils in the resin-rich ductile matrix could be correlated with the delamination mode.

Dry sliding wear behavior of epoxy composite reinforced with short palmyra fibers

The present work explores the possibility of using palmyra fiber as a replacement for synthetic fiber in conventional polymer composites for application against wear. An attempt has been made in this work to improve the sliding wear resistance of neat epoxy by reinforcing it with short palmyra fibers (SPF). Epoxy composites with different proportions (0, 4, 8 and 12 wt. %) of SPF are fabricated by conventional hand lay-up technique. Dry sliding wear tests are performed on the composite samples using a pin-on-disc test rig as per ASTM G 99-05 standards under various operating parameters. Design of experiment approach based on Taguchi's L16 Orthogonal Arrays is used for the analysis of the wear. This parametric analysis reveals that the SPF content is the most significant factor affecting the wear process followed by the sliding velocity. The sliding wear behavior of these composites under an extensive range of test conditions is predicted by a model based on the artificial neural network (ANN). A well trained ANN has been used to predict the sliding wear response of epoxy based composites over a wide range.

Three-dimensional hygromechanical analysis of fibre polymer composites: Effect of boundary conditions

Moisture diffusion through a unidirectional fibre reinforced polymer matrix composite is studied. The stresses due to the expansion of the matrix caused by moisture diffusion are evaluated. A three-dimensional (3D) micromechanical model is developed to study diffusion both across and along the fibre. The well-known 2D plane strain condition is modelled and validated as a special case of the 3D model. The utility of 3D modelling is further demonstrated to analyse the stress along the fibre length. It is demonstrated that the variation of boundary conditions along the fibre length has a dramatic effect on the stresses. The stresses along fibre length computed through finite element analysis (FEA) are compared against an analytical solution obtained from axi-symmetric concentric cylinder assemblage (CCA) model. This paper demonstrates the importance of 3D diffusion kinetics in unidirectional reinforced polymer composites.

Investigation of Plateau–Rayleigh Instability in Drawn Metal–Polymer Composite Fibers for Metamaterials Fabrication

We consider the drawing of composite metal–polymer fibers for wire array metamaterials fabrication. The metal is liquid during drawing and its surface tension results in diameter fluctuations, which lead to the metal breaking up into droplets, according to the Plateau–Rayleigh instability. For small fluctuations, we reconcile experimental results with a linear model for the instability adapted to fiber drawing. For larger fluctuations, we analyze the wavelength of fluctuations and observe sequential breakup on different length scales. An oxide layer is detected on the wires which may complicate surface interactions.

Bubble-filled silica microfibers from multiphasic flows for lightweight composite fabrication

Hollow spherical shells made of various oxides have long been used as filler materials to prepare light-weight materials with high specific strength. We present the fabrication of bubble-filled silica microfibers with controlled size and structure by using multiphase flow in a coaxial glass capillary device. The multiphase flow is controlled to generate a jetting gas-in-water-in-oil core–sheath stream, which is converted to flexible nanoparticle–polymer composite fibers filled with bubbles. The production rate of these bubble fibers can reach up to 2000cm/min. These flexible fibers can be manipulated to desired shapes or architectures and subsequently be sintered via thermal treatment. We demonstrate the fabrication of bubble fiber-filled light weight composite, which potentially has a significant advantage over conventional light-weight composites made with spherical hollow particles.

Analysis of natural fiber polymer composites: Effects of alkaline treatment on sound absorption

This study is focused on the development of sound absorbing materials based on natural fiber polymer composites. The natural fibers were modified through the alkaline treatment and the natural fiber polymer composites were fabricated using hot and cold compression hydraulic press machine. The sound absorption coefficients of the composites were measured using two-microphone transfer function impedance tube method. Characterizations of the natural fiber polymer composites were analyzed using scanning electron microscope and Fourier transform infrared spectroscopy. It was found that in all measured composites, the sound absorption coefficients increased as the frequency increased. Also, as the fiber loading increased, the sound absorption coefficients of the natural fiber polymer composites were increased. It was found that the alkaline treated fiber reinforced composites increased the sound absorption coefficients due to removal of impurities and change in the structure of composites. The alkaline treatment of fibers showed better adhesion interface between fiber and polymer as compared to untreated fibers. This can be seen clearly under morphological and spectral studies of the natural fiber polymer composites.

Influence of thermo-oxidative aging on the thermal conductivity of carbon fiber fabric reinforced epoxy composites

The present paper examined the thermo-oxidative aging (TOA) mechanism of the thermal conductivity of carbon fiber polymer composites (CF-PMCs) and the role of reinforced structure on the thermal conductivity of CF-PMCs under TOA conditions. The three dimensional and four directional braided carbon fiber/epoxy composites (BC), the laminated plain woven fabric/epoxy composites (LC), and the neat resins (NR) were investigated for up to 1200 h at 140 °C in air. The process resulted in progressive deterioration of the matrix rein and fiber/matrix interfaces, in the form of chain scissions, oxidization of carbon elements, weight loss, and cracks, which significantly led to the decrease of the thermal conductivity of the NR, LC, and BC. The ratio of fiber end area to the total surface area in a sample determined the rate of weight loss and the changes in thermal conductivity. The LC samples had 1.2 times higher ratio of fiber end area to the total surface area, and their loss in thermal conductivity and weight were significantly higher than that of BC samples at the same aging conditions. Besides, the thermal conductivity of CF-PMCs was highly negatively correlated with the weight loss under TOA conditions.

Degradation of Polyester-Based and Vegetable Fiber Polymeric Composites

Degradation of Polyester-Based and Vegetable Fiber Polymeric Composites

Solid waste-based hybrid natural fiber polymeric composites

The word hybrid composite defines the composite containing more than one type of fiber material as reinforcing fillers or additives. It has become an attractive property of hybrid composite than single fiber containing composite. Natural fiber hybrid composites are providing “eco-materials” to the world which has gained key importance in preserving our environment. Due to excess availability of industrial, agricultural, mining, and domestic solid wastes from the primary process, the environmental and ecological storing and disposal problems are created. In order to safeguard the environment, solid waste materials are used as good fillers for making natural fiber polymeric composites to improve its mechanical and moisture properties.

Enzyme‐mediated surface modification of jute and its influence on the properties of jute/epoxy composites

Surface modification of jute fibers is necessary to improve the adhesion and interfacial compatibility between fibers and resin matrix before using fibers in polymer composites. In this study, dodecyl gallate (DG) was enzymatically grafted onto the jute fiber by laccase to endow the fiber with hydrophobicity. A hand lay‐up technique was then adopted to prepare jute/epoxy composites. Contact angle and wetting time measurements showed that the surface hydrophobicity of the jute fabric was increased after the enzymatic graft modification. The water absorption and thickness swelling of the DG‐grafted jute fabric/epoxy composite were lower than those of the other composites. The tensile and dynamic mechanical properties of the jute/epoxy composites were enhanced by the surface modification. Scanning electron microscopy images revealed stronger fiber–matrix adhesion in composites with modified fibers. Therefore, the enzymatic graft modification increased the fiber–matrix interface area. The fiber–matrix adhesion was enhanced, and the mechanical properties of the composites were improved. POLYM. COMPOS., 38:1327–1334, 2017. © 2015 Society of Plastics Engineers