Polyetheretherketone composites reinforced with surface modified mica

Mica fillers reinforced polyetheretherketone (PEEK) composites were fabricated using compression molding technique. To improve embedding of the mica within the PEEK matrix, the mica surface was chemically modified using vinyl trimethoxysilane (VTMO), at variable concentration (0–1.5 wt%). The performance characteristics and treated mica PEEK at mica loading of 20 wt% composites were examined in terms of scanning electron microscopy, dynamic mechanical thermal analysis, and modulated differential scanning calorimetry. The tensile strength and modulus improved to the tune of 81 and 44% with treated mica‐filled PEEK composites. Mechanical tests revealed improved properties of VTMO‐treated mica/PEEK composites, which confirmed improved interfacial adhesion with chemical treatment. The increment of the dynamic modulus for the treated mica PEEK composites was also noticed to 82% as compared with untreated counterpart, at elevated temperatures of 250°C, indicating apparent improvement of high‐temperature mechanical properties. POLYM. COMPOS., 31:2121–2128, 2010. © 2010 Society of Plastics Engineers     

Effects of fibre type and matrix structure on the mechanical performance of self-compacting micro-concrete composites

The compatibility of matrix and fibre properties is one of the key parameters in the successful design of fibre reinforced cementitious composites. In order to achieve the desired performance, the properties of each constituent of composite should be properly configured. The aim of this study was to investigate the performance of two polymer based micro-fibres (polypropylene and polyvinyl alcohol) in different matrices (high strength and comparatively low strength with fly ash incorporation) which were designed to contain considerably high amounts of fibres (1% by volume) while maintaining their self-compactability. The fresh state thixotropic behaviour of fibre reinforced matrices was minimised by proper adjustment of water/cementitious material ratio and admixture dosage. The mechanical properties (first crack strength and displacement, flexural strength and relative toughness) of prismatic composite samples were compared by three point flexural loading test. The typical behaviours of selected composites and collapse mechanisms of PP and PVA fibres in these matrices were characterised by microstructural studies. It was concluded that, a high strength matrix with a high strength fibre give the best performance from the view point of flexural strength and toughness performance. However, incorporation of fly ash did not cause a significant reduction in composite performance possibly due to its enhancing effect on matrix–fibre interface adhesion. The possibilities and suggestions to further improve the performance of the composites were also discussed.     

Interlaminar fracture toughness of selectively stitched thick carbon fibre reinforced polymer fabric composite laminates

Abstract

Carbon fibre reinforced polymer fabric specimens prepared from selectively stitched thick laminates have been tested under mode I (tension) and mode II (shear) loading, similar to already established tests used for thin unidirectional specimens. The respective interlaminar fracture toughness characteristics were derived for laminates of different stitching configurations. Results indicated significant interlaminar fracture toughness increase for all stitched samples compared with non-stitched samples, especially under mode I loading. It was concluded from parametric investigations that carbon thread stitching is more effective than its aramid counterpart in improving interlaminar fracture toughness. This is attributable to its higher stiffness and better bonding to the carbon fibre reinforced polymer system compared with the aramid thread.     

玻璃纤维增强PEEK复合材料成型工艺研究

本文初步探索了玻璃纤维增强聚醚醚酮(PEEK)复合材料的成型工艺．通过力学性能、微观形貌分析等试验,探索了不同工艺参数对玻璃纤维增强PEEK复合材料性能的影响,进而制定了复合材料较优的成型工艺参数．其成型工艺参数包括冷却速度、成型压力、成型温度、保温时间．     

Temperature and loading rate effects in the mode II interlaminar fracture behavior of carbon fiber reinforced PEEK

The combined effect of varying loading rate and test temperature on the mode II interlaminar fracture properties of AS4/carbon fiber reinforced PEEK has been investigated. End notch flexure tests have shown that this thermoplastic‐based composite system offers a very high value of interlaminar fracture toughness at room temperature. Increasing the test temperature leads to a reduction in the mode II interlaminar fracture toughness of the composite, with the value at 150°C being approximately one half of the room temperature value. In contrast, increasing the crosshead displacement rate has been shown to increase the value of G_IIc by up to 25%. A more detailed understanding of the effect of varying temperature and loading rate on the failure mechanisms occurring at the crack tip of these interlaminar fracture specimens has been achieved using the double end notch flexure (DENF) geometry. Here, extensive plastic flow within the crack tip region was observed in all specimens. It is believed that the rate sensitivity of G_IIc reflects the rate‐dependent characteristics of the thermoplastic resin.     

Effects of sorbed caprolactam on the crystallinity,morphology, and deformation behavior of polyetheretherketone and poly(phenylene sulfide)

Studies on the high temperature sorption of caprolactam by polymer resins and their composites have been conducted. The systems investigated were glass fiber reinforced (GFR) poly(phenylene sulfide) (PPS), polyetheretherketone (PEEK) neat resin, GFR PEEK and carbon fiber reinforced (CFR) PEEK. To measure changes of caprolactam sorption, melting behavior, mechanical properties, and fracture surface morphology were determined. Absorption of caprolactam by the PEEK composites was 30 to 40 percent less than by the neat resin. This is attributed to the fibers, which acted to constrain the matrix and thus limit its swellability. Reductions in melt temperature, percent crystallinity, ultimate tensile strength, and modulus were observed following exposure to the chemical environment. The loss of strength and stiffness was a consequence of the degradation of the matrix/fiber interface by the sorbed caprolactam.     

High performance PEEK/carbon nanotube composites compatibilized with polysulfones-II. Mechanical and electrical properties

The mechanical and electrical properties of poly(ether ether ketone) (PEEK)/single-walled carbon nanotube (SWCNT) composites with polysulfones as compatibilizers have been analyzed. Dynamic mechanical studies reveal that these composites exhibit considerably higher storage modulus and glass transition temperature than non-compatibilized samples. Tensile tests indicate a non-linear growth in the Young’s modulus and strength with increasing SWCNT loading, related to changes in the degree of crystallinity of the composites. The moduli of samples with very low CNT content exceed the predictions by the rule of mixtures, whilst at higher concentrations fall slightly below the theoretical values. The addition of the polysulfones increases the stiffness and toughness of the composites, attributed to an improved filler dispersion and stronger matrix-reinforcement interfacial adhesion. Fractography analyses suggest that these compatibilizers favor the ductile deformation of the matrix. The electrical and thermal conductivities of the composites decrease slightly in the presence of the polysulfones, albeit are well above the values of pure PEEK. Enhanced properties are found for samples including wrapped laser-grown SWCNTs. The overall mechanical performance of the compatibilized composites is suitable for use in lightweight structural applications, particularly for the aeronautic industry.     

Hemp fibre as alternative to glass fibre in sheet moulding compound Part 1 – influence of fibre content and surface treatment on mechanical properties

Abstract

Hemp fibre mat reinforced unsaturated polyester composites were fabricated using a conventional sheet moulding compound process. The influence of fibre and CaCO₃ filler content on strength and stiffness of these hemp fibre reinforced sheet moulding compounds is reported and compared with data for chopped glass fibre reinforced sheet moulding compounds. In addition the influence of alkaline and silane treatments of the hemp fibres is evaluated. The experimental data are compared to modified versions of the Cox–Krenchel and Kelly–Tyson models, supplemented with parameters of composite porosity to improve the prediction of composite tensile properties. A good agreement was found between the modified models and experimental data for strength and stiffness. The results indicate that hemp fibre reinforced sheet moulding compounds are of interest for low cost engineering applications that require high stiffness to weight ratios.     

Influence of carbon nanotubes on the thermal, electrical and mechanical properties of poly(ether ether ketone)/glass fiber laminates

Novel poly(ether ether ketone) (PEEK)/single-walled carbon nanotube (SWCNT)/glass fiber laminates incorporating polysulfone as a compatibilizing agent were fabricated by melt-blending and hot-press processing. Their morphology, mechanical, thermal and electrical properties were investigated and compared with the behavior of similar non-compatibilized composites. Scanning electron micrographs demonstrated better SWCNT dispersion for samples with polysulfone. Thermogravimetric analysis indicated a remarkable improvement in the thermal stability of PEEK/glass fiber by the incorporation of SWCNTs wrapped in the compatibilizer, ascribed to a significant thermal conductivity enhancement. Differential scanning calorimetry showed a decrease in the crystallization temperature and crystallinity of the polymer with the addition of both wrapped and non-wrapped SWCNTs. The laminates exhibit anisotropic electrical behavior; their conductivity out-of-plane is lower than that in-plane. Dynamic mechanical studies revealed an increase in the storage modulus and glass transition temperature in the presence of polysulfone. Mechanical tests demonstrated significant enhancements in stiffness, strength and toughness by the incorporation of wrapped nanofillers, whilst the mechanical properties of non-compatibilized composites only improved marginally. Samples with laser-grown SWCNTs exhibit enhanced overall performance. This investigation confirms that SWCNT-reinforced PEEK/glass fiber compatibilized composites possess excellent potential to be used as multifunctional engineering materials in industrial applications.     

聚醚醚酮复合材料摩擦学性能研究现状

介绍聚醚醚酮(PEEK)的基本物理化学性能,评述粒子填充、纤维增强、有机-无机共混和等离子处理PEEK复合材料的摩擦磨损性能研究进展,指出今后应加强对多因素协同作用下PEEK复合材料磨损机理、开展PEEK复合材料微观摩擦学及生物摩擦学方面的研究。     

Mechanical behavior and fracture toughness characterization of high strength fiber reinforced polymer textile composites

The mechanical and fracture behavior of polymer composites are the subject of great interest from many years and still interesting among the researchers. Composites are extremely used for their superior mechanical, thermal and fracture toughness properties in various sectors such as automobile, aerospace and defense applications. In this article, unidirectional and woven high strength glass, carbon and Kevlar fiber reinforced polymer textile composites are taken into consideration for the comprehensive review of mechanical behavior and fracture toughness characterization. Current review work began with the introduction to polymer textile composites with its manufacturing stages, processing techniques and factors affecting the performance under mechanical loading. The mechanical behavior of high strength fiber reinforced polymer (HSFRP) textile composites was discussed in tension, compression, flexural, low velocity and high velocity impact loading with the recent numerical and experimental characterization studies. Textile geometrical modeling and CAE tools are also described for numerical characterization. Under the influence of mechanical loading on composites, failure occurs actually due to the crack initiation and propagation, so it is also required to characterize. Significant elements of fracture mechanics are well described for the better understanding of fracture toughness characterization. Mode-I, Mode-II, Mode-III interlaminar and Mode-I intralaminar fracture toughness characterization are widely explained by considering the effect of filler content, fiber orientation and fiber volume fraction. Fracture toughness characterization techniques and research summery are uniquely presented by considering various factors under one umbrella for better understanding of fracture behavior. Statistical Weibull distribution is also presented for the failure prediction of composites.

     

Highly efficient preparation of multi-angle continuous carbon fibre reinforced hydroxyapatite composites by electrostatic splitting method

An electrostatic splitting device was self-designed and manufactured for highly efficient preparation of multi-angle continuous carbon fibre (CF)-reinforced ceramic-based composites and was used to prepare multi-angle continuous CF and nano-hydroxyapatite (nHA)-coated CF reinforced HA composites with improved CF dispersion and content. The compressive strength of sintered [0°/90°] CF reinforced hydroxyapatite (CF/HA) composites is more than two and a half times that of hydroxyapatite and is superior to that of cortical bone (26.42–110.7%). Compared with hydroxyapatite, fracture toughness of [0°/0°], [0°/90°] and [? 45°/+ 45°] CF/HA composites increase by 28.83%, 66.32% and 115.95%, respectively. The strength and fracture toughness (30.2 MPa·m^1/2) of [? 45°/+ 45°] CF/HA bioceramics display synchronously improving. Micromechanical property and crack propagation process of the composites were simulated in depth. Based on optimised dispersion and arrangement of CF, the introduction of nHA coating enhances the mechanical properties of nHA-coated CF reinforced HA composites because nHA coating can block the generation and propagation of cracks.     

Thermal Aging Properties of Graphite Fiber Reinforced Peek and Graphite Fiber Reinforced Bmi Composites

Graphite fiber reinforced poly(ether ether ketone) (PEEK) and graphite fiber reinforced bismaleimide (BMI) composite materials are two kinds of advanced fiber-reinforced polymer matrix composites with good thermal stability and excellent mechanical properties at high temperature. They are currently receiving considerable attention. the main limitation on their application is the lack of knowledge regarding their behaviors during extended use at high temperature. Thermal aging properties are the main parameters for new polymer matrix composites that will be used in advanced spacecraft structural components. From the results of thermal aging effects on the properties—including interlaminar shear strength, drop-weight impact strength, and impact energy—of graphite/PEEK and graphite/BMI composites, it is found that unidirectional graphite fiber reinforced composites retain higher strength compared to multidirectional, and that multidirectional graphite/PEEK composites keep higher property retentions than multidirectional graphite/BMI composites after thermal aging at 190°C. From scanning electron photomicrographs, it is also found that graphite/PEEK composites have better fiber/resin adhesion, intraply adhesion, and microcrack resistance compared to graphite/BMI composites after thermal aging.     

Effect of physical aging on the toughness of carbon fiber-reinforced poly(ether ether ketone) and poly(phenylene sulfide) composites. I

The effect of physical aging on the penetration impact toughness and Mode I interlaminar fracture toughness of continuous carbon fiber (C.F.) reinforced poly(ether ether ketone) (PEEK) and poly(phenylene sulfide) (PPS) composites has been investigated by using an instrumented falling weight impact (IFWI) technique and a double cantilever beam (DCB) test. Composite materials studied are aged below their glass transition temperature (T_g) at various periods. Initiation force and energy of damage, failure propagation energy, impact energy and ductility index (D.I.) are reported. The Mode I critical value of strain energy release rate (G_IC) of the unidirectional carbon fiber-reinforced PEEK (APC-2) composites is obtained. Results show that aging has a significant effect on the toughness of both composite materials. Energy absorbed during impact decreases with the increase of aging temperature and period. The PEEK/C.F. composites exhibit a higher retention of impact toughness than that of the PPS/C.F. composites after aging; however, the PPS/C.F. composites show a much higher ductility index. The Mode I fracture mechanism of the APC-2 composite is a combination of stable and unstable failure and shows a “stick-slip” behavior. Owing to the formation of a relative rigid structure, the fracture toughness (G_IC) of APC-2 decreased with the increase of aging temperature and period.     

Effect of the addition of silane coupling agents on the properties of wollastonite‐reinforced poly(ether ether ketone) composites

The wollastonite was grafted with different silane coupling agents, which could improve interface adhesion. Wollastonite and modified wollastonite‐reinforced poly(ether ether ketone) (PEEK) composites were prepared by melt blending. The mechanical properties, rheology behavior, and thermal properties of the composites were investigated. The modified wollastonite‐reinforced PEEK composites exhibited better mechanical properties than the unmodified wollastonite‐reinforced PEEK composites based on good interfacial adhesion. The composites had lower activation volume and complex shear viscosity. Furthermore, the modified wollastonite‐reinforced PEEK composites had higher crystallization peak temperature (T_c) and crystalline fraction (χ_c) compared with the unmodified wollastonite‐reinforced PEEK composites. This study shows that the traditional silane coupling agents could effectively improve the performance of PEEK composites. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Fatigue crack growth in fiber reinforced plastics

Crack extension during fatigue loading is one of the primary causes of failure in engineering materials. While the fatigue crack resistance of homogeneous and even adhesive systems has received detailed study and characterization, relatively few and scattered results are available for fiber composites. One difficulty with obtaining such data for composites is their tendency to develop complex patterns of intra- and interlaminar damage which expand in a stable manner during fatigue. Such damage usually does not severely reduce the load carrying capacity of a structure but the complexity of the damage geometry has so far frustrated efforts to apply any unifying theories of growth. Measurement of the rate of macroscopic crack growth, through thickness crack extension, has been possible for certain composites and crack direction where the stable damage is constrained. These include cracks in 0°/90° laminates, woven fabric laminates, chopped strand mat laminates, sheet molding (SMC) materials, and short fiber reinforced thermoplastics. Macroscopic interlaminar cracks in continuous fiber systems have also received some recent attention. Fatigue crack growth in glass fiber composites for which most data are available, involves significant contributions from both static and cyclic load effects. A simple model for predicting fatigue crack growth rates from traditional S-N curve and fracture toughness data has proven useful for certain well behaved systems. Limited study has also been made of the effects of moisture and salt water on the fatigue crack growth rate.     

Effect of surface modification of fly ash reinforced in polyetheretherketone composites

Fly ash reinforced polyetheretherketone (PEEK) composites were fabricated using compression molding technique. The fly ash surface was chemically modified using vinyltrimethoxy silane and 3‐aminopropyltriethoxy silane. The properties of treated fly ash PEEK composites were examined in terms of scanning electron microscopy, dynamic mechanical thermal analysis, differential scanning calorimetry, and thermo gravimetric analysis. The modified fly ash was observed to disperse more uniformly than the unmodified counterpart. The tensile strength and modulus also improved with treated fly ash filled PEEK composites. The increment of the dynamic modulus for the PEEK/treated fly ash composites is 32% at 250°C, indicating apparent improvement of high temperature mechanical properties. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers.     

Effect of Impact Modifier Types on Mechanical Properties of Rubber‐Toughened Glass‐Fibre‐Reinforced­ Nylon 66

The effect of adding rubber on the properties of glass‐fibre‐filled nylon 66 was investigated in this study. Styrene‐Ethylene‐Butylene‐Styrene and Ethylene‐Propylene elastomers grafted with maleic anhydride (SEBS‐g‐MA and EP‐g‐MA, respectively) were used to toughen the nylon‐matrix composites. Impact strength and elongation at break were found to increase with increasing rubber content, but flexural strength, tensile strength and stiffness decreased; however, by adding moderate amounts of rubber to glass‐fibre‐reinforced nylon 66, a desirable balance between stiffness and toughness of the material may be obtained. For example, the addition of 10 wt.% of SEBS‐g‐MA to nylon 66 with 23.62 wt.% glass fibre loading resulted in 28.3% and 167% increase in tensile strength and impact strength of the composites, respectively, when compared to neat nylon 66. This suggests that combining both glass fibres and rubber with nylon 66 is a useful strategy to optimize and enhance the properties of nylon 66. The procedure may be used to recycle polyamides, in general, and to develop components for under‐the‐hood automotive applications, in particular.     

Mechanical,Thermal and Morphological Properties of Grewia Optiva Fiber/Polymer Matrix Composites

This work is concerned with the evaluation of properties of compression molded Grewia Optiva fiber reinforced Resorcinol-Formaldehyde (RF) matrix-based polymer composites. Reinforcing of the RF resin with Grewia Optiva fiber was done in the form of particle size (200 micron). Present work reveals that mechanical properties such as: tensile strength, compressive strength, flexural strength and wear resistance of the RF matrix have been found to increase up to 30% fibre loading (in terms of weight) and then decreases for higher loading. Morphological and thermal studies of the matrix, fibre and particle reinforced (P-Rnf) green composites have also been studied.     

Is spark plasma sintering suitable for the densification of continuous carbon fibre - UHTCMCs?

For the first time we show that spark plasma sintering can efficiently replace hot pressing for the densification of UHTCMCs, in the present case ZrB₂/SiC composites reinforced with continuous carbon fibres. To this purpose, the same materials were first produced by hot pressing as baseline samples and then by spark plasma sintering (SPS) to compare microstructure and basic mechanical properties. A special emphasis was given to the study of interfaces, in case of both coated and uncoated carbon fibres.SPS allowed for faster sintering but required an adjustment of the temperature to avoid fibre degradation compared to hot pressing. With similar porosity levels, we observed a slight decrease of flexural strength (300 vs 470 MPa), and an improvement of fracture toughness (15 vs 10 MPa√m) for SPSed samples. SPS was proved to be an effective method for the consolidation of continuous fibre reinforced UHTC composites.