Enhanced thermal properties for epoxy composites with a three-dimensional graphene oxide filler

In this study, we report a simple and efficient method to prepare three-dimensional graphene oxide (3DGO) network by freeze drying and investigate the effect of 3DGO network on thermal properties of epoxy composites. It was found that the 3DGO network not only improved thermal conductivity, thermal stability, glass transition temperature and storage modulus of epoxy composites, but also reduced the thermal expansion properties of epoxy composites. For instance, the thermal conductivity value of epoxy composite with only 1.3 wt% 3DGO is 0.62 Wm^-1K^-1, increased by 148 % in comparison with that of the neat epoxy (0.25 Wm^-1K^-1).     

Mechanical,thermal and interfacial properties of green composites from basalt and hybrid woven fabrics

Composites based on pure Basalt and Basalt/Jute fabrics were fabricated. The mechanical properties of the composites such as flexural modulus, tensile modulus and impact strength were measured depending upon weave, fiber contents and resin. Dynamic mechanical analysis of all composites were done. From the results it is found that pure basalt fiber combination maintains higher values in all mechanical tests. Thermo-gravimetric (TG/DTG) composites showed that thermal degradation temperatures of composites shifted to higher temperature regions compared to pure jute fabrics. Addition of basalt fiber improved the thermal stability of the composite considerably. Scanning electron microscopic images of tensile fractured composite samples illustrated that better fiber-matrix interfacial interaction occurred in hybrid composites. The thermal conductivity of composites are also investigated and thermal model is used to check their correlation.     

Mechanical and thermal properties of recycled poly(ethylene terephthalate) reinforced newspaper fiber composites

This study presents the mechanical and thermal properties of environment-friendly composites made from recycled newspaper fibers reinforced recycled poly(ethylene terephthalate) (rPET) resin with the addition of styrene-ethylene-butylene-styrene grafted maleic anhydride (SEBS-g-MA) as compatibilizer. The effect of SEBS-g-MA addition (i.e., 10 phr) by using a twin-screw extruder to the rPET resin, followed by different fiber content (5, 10 and 15 wt.%) on the tensile, flexural and impact properties of the composites were determined. Stiffness of composites increased significantly compared to those of rPET/SEBS-g-MA blend. Fiber addition resulted in moderate increases in both tensile and flexural strength of the composites. Scanning electron microscope (SEM) photomicrographs of the impact fracture surfaces demonstrate good adhesion at 5 and 10 % fiber content. Differential scanning calorimetry (DSC) showed that the presence of newspaper fibers enhanced the nonisothermal crystallization kinetics and crystallinity. Thermal stability of the composites was improved as indicated by thermogravimetric analysis (TGA).     

Mechanical properties of uniaxial natural fabric Grewia tilifolia reinforced epoxy based composites: Effects of chemical treatment

The effects of chemical treatment on the mechanical, morphological, and chemical resistance properties of uniaxial natural fabrics, Grewia tilifolia/epoxy composites, were studied. In order to enhance the interfacial bonding between the epoxy matrix and the Grewia tilifolia fabrics, two different types of treatment: alkali treatment (5 % NaOH) and (3-aminopropyl)-triethoxysilane coupling agent (CA), were used. The epoxy composites containing 0–15 wt% of Grewia tilifolia fabric were prepared by hand lay-up technique, at room temperature. The tensile and flexural properties of the untreated, alkali-treated and coupling agent treated Grewia tilifolia reinforced epoxy composites were determined as a function of fabric loading. The 9 % wt Grewia tilifolia fabric reinforced epoxy composites showed improved tensile and flexural modulii when compared to the neat epoxy matrix. Significant improvement in the mechanical properties was obtained when both alkali and coupling agent treated fabrics were used as reinforcement. Morphological studies demonstrated that better adhesion between the fabrics and the matrix was achieved especially when the alkali-treated and coupling agent treated Grewia tilifolia fabrics were used in the composites. For the water absorption and chemical resistance studies, various solvents, acids and alkalis were used on the epoxy composites. This study has shown that Grewia tilifolia fabric/epoxy composites are promising candidates for structural applications, where high strength and stiffness are required.     

Mechanical and thermal properties of josapine pineapple leaf fiber (PALF) and PALF-reinforced vinyl ester composites

Although the pineapple leaf fibers (PALF) are long known as domestic threading material in Malaysia, they are currently of little use despite being mechanically and environmentally sound. This study evaluated some selected properties of Josapine PALF and PALF-vinyl ester composites as well as the effects of simple abrasive combing and pretreatments on fiber and composite properties. Using PALF vascular bundles extracted from different parts of the leaves did not significantly affect PALF-vinyl ester composite mechanical properties. At low weight fraction and consolidating pressure, PALF fibers regardless of diameters and locations performed equally well in enhancing composite flexural properties under static loading. Finer bundles enhanced PALF-vinyl ester composite toughness indicated by tests at higher speeds. Abrasive combing produces cleaner and finer bundles suitable for reinforcing composites for applications not requiring high toughness.     

Improved interfacial properties of carbon fiber/epoxy composites through graphene oxide-assisted deposition of carbon nanotubes on carbon fiber surface

A useful reinforcement for carbon fiber (CF) composites was found by performing the assisted electrophoretic deposition (EPD) of graphene oxide (GO) for carbon nanotubes (CNTs) onto the CF surface. GO-assisted EPD of CNTs was conducted without the use any other pre-treatment or additives in order to avoid destroying the structure of the CNTs and to facilitate preparation of stable dispersion that was suitable for EPD. The presence of GO-CNTs may effectively increase both the roughness and wettability of the CF surface, resulting in an improvement to the interfacial bonding strength between the CF and the epoxy (EP). In contrast to the pristine CF/EP composite, the GO-CNTs/CF/EP composite exhibited a 64.6 % increase in interlaminar shear strength. Meanwhile, the water absorption of the composites decreased from 0.36 wt.% to 0.14 wt.%. The variable surface morphology, surface roughness, surface free energy and surface chemical composition of the CF were considered to have had an effect on the interfacial properties of the CF/EP composites; these effects could be seen using atomic force microscopes, scanning electron microscopes, X-ray photoelectron microscopes and contact angle analysis characterizations.     

Morphological and thermal properties of maize fiber composites

Maize stalk has become one of the major sources of fibers from the agricultural residues. Use of these fibers as a reinforcement in the polymer is described in this paper. The present work is focused on establishing the properties such as physical, chemical, morphological structure and thermal properties of maize stalk fiber using different characterization techniques. Simple hand layup method was followed for processing the composite material. Chemical treatments of fibers were carried out to study the interaction of fibers with the matrix. The results revealed that maize fibers can also be used as a traditional fiber as reinforcement in a natural fiber reinforced composite materials.     

The influence of graphene reinforced electrospun nano-interlayers on quasi-static indentation behavior of fiber-reinforced epoxy composites

The aim of this research is to investigate the development and evaluation of hybrid multi-scale aramid/epoxy composites interleaved with electrospun graphene nanoplatelets/nylon 66 (GNPs/PA66) mats. The reinforced nanofiber mats were explored for their best mechanical properties and PA66 nanofibers with 1 wt% GNPs were selected for composite production. Quasi-static indentation tests were performed on both pristine and nanofiber-modified composites. The experimental results revealed that the introduction of reinforced interleaves within the interlaminar interfaces of composites promotes fracture toughness compared to pristine interleaves. It is shown that there is a particular interleaf thickness for optimum toughening effect of nanofibers. The optimum thicknesses for pristine and reinforced interleaves are 35 and 17.5 μm, respectively.     

Mechanical properties of rice straw fiber-reinforced polymer composites

Rice straw fibers have been used as reinforcing fillers in different polymers, tow composites were prepared by using polyvinyl alcohol and polystyrene polymers with different ratio of polymers. The pressed samples were subjected to various electron beam irradiation dose. The results indicated that, flexural strength, impact strength and modulus of elasticity increase with increasing the polymer ratio in the mix composition. It was found that the water absorption and thickness swelling percentages of rice straw fiber polystyrene composites decrease with increasing the polystyrene content in the same composition, while its values for rice straw polyvinyl alcohol composites improve. These are attributed to hydrophobic and hydrophilic characteristics of the tow composites. The improvement of physico-mechanical properties of both composites with the increase of electron beam irradiation dose are probably attributed to randomly initiated chain reactions, which started by the reactive centers created by electron beam. These observations were confirmed by IR spectrometer and SEM studies.     

Mechanical and thermal properties of polypropylene (PP) composites filled with CaCO3 and shell waste derived bio-fillers

The clam shell (CS) waste was first modified by furfural and hydrochloric acid to prepare fillers FCS and ACS, which were then used as fillers in polypropylene (PP), as well as the commercial calcium carbonate (CC). These fillers were characterized and analyzed by means of X-ray diffraction (XRD), atomic force microscopy (AFM), particle size analyzer, Fourier transformed infrared spectroscopy (FTIR) and contact angle measurement. The mechanical and thermal properties of PP composites were investigated as well. XRD analysis indicated that the major crystalline phase of CC was calcite; of shell waste derived fillers, calcite and aragonite. The CC was fully hydrophobic, while the shell derived fillers were amphiphilic. Mechanical property studies showed that the incorporation of FCS played the role mainly of toughening the PP; of CC, CS and ACS, that of reinforcing. The optimum filler contents of CS, ACS and FCS could reach 5, 7 and 15 wt.%, respectively, to obtain a good balance between fracture toughness and stiffness of the PP composites. Polarized optical microscopy (POM) observation indicated that the inclusion of these fillers could promote the heterogeneous nucleation of PP.     

Enhanced thermal conductivity for PVDF composites with a hybrid functionalized graphene sheet-nanodiamond filler

A new thermal conductive poly(vinylidene fluoride) (PVDF) composite has been developed via a hybrid functionalized graphene sheets (FGS)-nanodiamonds (NDs) filler by a simple solution method. The PVDF composite showed different thermal conductivities at different proportion of hybrid filler. The thermal conductivity of the composite was up to 0.66 W/m·K for a mixture containing 45 wt% hybrid filler, which is about 2-fold increment in comparison to the PVDF martrix. The PVDF composites consisting of 20 wt% hybrid FGS/ND filler at the weight ratio of 1:3 shows the best thermal stability. The electrical conductivity of composites was increased from 5.1×10^?15 S cm^?1 (neat PVDF) to 7.1×10^?7 S cm^?1 of the PVDF composite with 10 wt% hybrid filler.     

Enhancement of thermal and physical properties of epoxy composite reinforced with basalt fiber

The basalt chopped fiber reinforced epoxy composites using different curing systems were prepared in order to investigate the thermal characteristics of the composites. 2 different curing systems for bisphenol F type epoxy resin — an epoxy-amine curing system and an epoxy-anhydride curing system — were selected and used to investigate the interaction between matrix resin and basalt fiber in the means of thermal properties and physical properties. Through the evaluation of T _g and thermal degradation behavior of both systems, it was deduced that the type of curing system as well as basalt fiber reinforcement have a great role in determining thermal properties of the composites. Also, the tensile and flexural properties of the composites were systematically evaluated in order to further understand the effect of curing agents on the interaction with basalt fiber.     

Preparation and thermal properties of polyphenylene sulfide/organic montmorillonite composites

Cetyl trimethyl ammonium bromide (CTAB) was used for the intercalation modification of nano-montmorillonite (MMT). The spectra of Fourier transform infrared spectrometer (FTIR) and X-ray diffraction (XRD) suggested that CTAB had intercalated into the layers of MMT. And the interlayer spacing of MMT increased from 1.198 to 3.616 nm. The thermogravimetric analysis (TGA) curves of organic montmorillonite (OMMT) showed three-step degradation. The scanning electron microscope (SEM) photographs showed that surface morphology of MMT remained unchanged. Then polyphenylene sulfide (PPS)/organic montmorillonite (OMMT) composites were prepared by melt blending. And composites were treated at 180 °C for 24 h. The results of SEM showed that OMMT had good dispersion behavior and adhesion with PPS. The results of differential scanning calorimetry (DSC) showed the addition of OMMT resulted in heterogeneous nucleation crystallization of PPS. The results of TGA showed there was a good improvement of the thermal stability of PPS. The FTIR and color measurement analysis showed the addition of OMMT could improve the thermal oxidation stability.     

Mechanical properties,morphology and dynamic mechanical properties of LGF/TPU/SAN composites

A series of the long glass fiber reinforced thermoplastic polyurethane elastomers and poly (styrene-acrylonitrile) (LGF/TPU/SAN) composites with different contents of long glass fiber were prepared by using self-designed impregnation device. Dynamic mechanical properties of TPU/SAN matrix reinforced with 10, 20 and 30 % by weight long glass fibers have been investigated by using dynamic mechanical thermal analysis (DMA). The results indicated that the content of long glass fiber and scanning frequency had some influence on dynamic mechanical properties and glass transition of LGF/TPU/SAN composites. In addition, the Arrhenius relationship has been used to calculate the activation energy of a-transition of the LGF/TPU/SAN composites. SEM demonstrates the relatively good dispersion of the long glass fiber in the TPU/SAN matrix. In addition, Effects of the content of long glass fiber on mechanical properties of the LGF/TPU/SAN composites are investigated.     

Mechanical and water absorption properties of woven jute/banana hybrid composites

This work aims to predict the mechanical properties of woven jute/banana hybrid composite. Woven fabrics are arranged in three layers of different sequence. Resin used in this work is Epoxy LY556 with hardener HY951. Composite specimen are prepared by hand-layup techniques. The effect of layering sequence on the mechanical properties namely tensile, flexural and impact was analysed. It is found that the tensile and flexural strength of hybrid composite (Banana/Jute/Banana) is higher than that of individual composites. Similarly, the impact strength of Jute/Banana/Jute hybrid composite is better than other types of composite. It is found that the moisture absorption of woven banana fiber composite is lesser than the hybrid composite. Fractography study of the fractured specimen is carried out using scanning electron microscope to analyse the fracture behaviour of the hybrid composite.     

Effect of Ni-coated short carbon fibers on the mechanical and electrical properties of epoxy composites

Ni-coated short carbon fibers (Ni-SCFs) were prepared using an electrodeposition method. Short carbon fiber (SCF) reinforced epoxy composites were prepared by changing the fiber content (0.1–0.7 wt%). To investigate the effect of Ni-coated short carbon fibers on the mechanical and electrical properties of the composites, we prepared two kinds of reinforcements: the short carbon fibers treated by 400 °C (400 °C treated SCFs) and Ni-SCFs. Fracture characteristics of the composites revealed the Ni coatings and the epoxy matrix had a better interface, so that the results of tensile and bending strength were better in epoxy/Ni-SCFs composites than those in epoxy/400 °C treated SCFs composites. The 400 °C treated SCFs decreased the electrical resistivity of the epoxy composites, compared to the pure epoxy. However the epoxy/Ni-SCFs composites had lower electrical resistivity than epoxy/400 °C treated SCFs with the same fiber content.     

Some of the mechanical and thermal properties of wheat straw filled-PP composites

The objective of this investigation was to evaluate the mechanical, thermal stability and viscoelastic behaviors of experimental PP composites made from wheat straw and PP-g-MA coupling agent. Four levels of wheat straw, 10, 20, 25 and 30 wt % and two levels of coupling agent, 0 and 3 % wt were mixed with PP in rotary type mixer and injection molding process, respectively. Tensile characteristics and impact strength, thermal gravity and dynamic mechanical and thermal analysis of the samples were evaluated. Based on the results, it was observed that the tensile properties increased and impact strength decreased with the increase in the fiber loading from 10 % to 30 %. Further, the composites treated with PP-g-MA exhibited improved mechanical properties which confirmed efficient fiber-matrix adhesion. DMT analysis showed that the PP composites made of 30 % wheat straw containing 3 % PP-g-MA showed the highest E’ and lowest tan δ than the untreated ones. Also, the thermal stability of wheat straw was lower than PP and as filler content in the composites increased, the thermal stability decreased and the ash content increased.     

Mechanical properties of flax-g-poly(methyl acrylate) reinforced phenolic composites

In order to develop composites with better mechanical properties and environmental performance, it becomes necessary to increase the hydrophobicity of the natural fibers and to improve the interface between matrix and natural fibers. Graft copolymerization of natural fibers is one of the best methods to attain these improvements. Only few workers have reported the use of graft copolymers as reinforcing material in the preparation of composites. So in the present paper, we report the preparation of graft copolymers of flax fibers with methyl acrylate (MA) using Fenton’s reagent (FAS-H₂O₂) as redox system. Synthesized flax-g-poly(MA) was characterized with FTIR, TGA/DTA, scanning electron microscopy (SEM), and X-ray diffraction (XRD) techniques. Composites were prepared using flax-g-poly(MA) as a reinforcement and phenolformaldehyde (PF) as the binding material. Mechanical properties of phenol-formaldehyde composites were compared and it has been found that composites reinforced with flax-g-poly(MA) showed improvement in mechanical properties. Composites reinforced with flax-g-poly(MA) showed better tensile strength (235 N) and compressive strength (814 N) in comparison to composites reinforced with original flax fiber which showed lesser tensile strength (162 N) and compressive strength (372 N). Composites reinforced with flax-g-poly(MA) shows the improved MOR, MOE, and SP.     

Mechanical properties of composites made from locally manufactured carbon fabrics and the composites produced from air-textured glass yarns

Composite materials have a wide range of applications in structural components because of their high strength-to-weight and stiffness-to-weight ratios. However, the most crucial and common life-restricting crack growth mode in laminated composites i.e. delamination is of great concern. Air jet texturing was selected to provide a small amount of bulk to the glass yarn. The purpose was to provide more surface contact between the fibres and resin and also to increase the adhesion between the neighbouring layers. These were expected to enhance the resistance to delamination in the woven glass composites. The development and characterisation of core-and-effect textured glass yarns was presented in the previous paper. This paper describes the comparison of the mechanical properties of composites produced from air-textured glass yarns and the composites made from locally manufactured carbon fabrics. The tensile, flexure and inter-laminar shear strength (ILSS) were compared and it was observed that although glass fibres are inferior to carbon fibres in terms of mechanical properties however, the flexure strength and ILSS of glass based composites increases after texturing and were found closer to the properties of carbon based composites.     

Mechanical,thermal and water absorption properties of plasticised sago pith waste

This paper provides an insight into the potential of utilising sago pith waste (SPW) to produce composite material. SPW is a fibrous waste that is produced as a result of the sago starch extraction process. It is made up of more than 60 % in weight of sago starch and was successfully converted into natural fibre reinforced thermoplastic starch composite using twin screw extrusion in the presence of different quantities of glycerol and water as plasticisers. No binder was added throughout the process. Good fibre-matrix compatibility was proven by SEM. Due to phase separation and fibre agglomeration, tensile strength of the composite decreased with increasing glycerol content while elongation at break remained unchanged at low values. Activation energies, Ea of the composites were computed from thermogravimetric analysis (TGA) data using Broido and Coat-Redfern equations. The obtained Ea values indicated that plasticisation led to the reduction in thermal resistance of SPW. It is suggested that blending the plasticised SPW with sago starch and polyvinyl alcohol will greatly improve upon the existing shortcomings, potentially resulting in useful consumer products from SPW, an unutilised, water polluting waste.