The fracture properties of a smart fiber metal laminate

This paper investigates the interfacial, tensile, and fatigue properties of a novel smart fiber‐metal laminate (FML) based on a nickel‐titanium (Ni‐Ti) shape memory alloy and a woven glass fiber reinforced epoxy. Initial tests, using the single cantilever beam (SCB) geometry, have shown that this unique system offers high values of metal‐composite interfacial fracture toughness. Tensile tests have shown that the mechanical properties of these FMLs lie between those offered by its constituent materials and that their tensile modulus and strength can be easily predicted using a rule of mixtures approach. Tension‐tension fatigue tests have shown that the fatigue performance of notched smart FMLs is superior to that offered by the plain Ni‐Ti alloy. A subsequent optical examination of unnotched laminates tested to failure under tension‐tension fatigue loading has shown that the fracture mechanisms occurring within the Ni‐Ti FMLs are strongly dependent on the applied cyclic stress. POLYM. COMPOS., 28:534–544, 2007. © 2007 Society of Plastics Engineers     

Environmental effects on glass fiber reinforced polypropylene thermoplastic composite laminate for structural applications

This article presents the mechanical and microstructural characterization of glass fiber reinforced polypropylene thermoplastic composite laminates (PP/Glass) exposed to tap water, salt solution, and freeze/thaw cycles. PP/Glass specimens were immersed at 23, 50, and 70°C in tap water to simulate the relative humidity of the direct environment and in a salt solution of 3% NaCl to simulate the effect of de‐icing salt. The measured flexural strengths of the specimens before and after exposure were considered as a measure of the durability performance of the specimens and were used for long‐term properties prediction based on the Arrhenius theory. In addition, the durability of PP/Glass to freeze/thaw cycles was studied for as received specimens and specimens saturated with tap water. Scanning electron microscopy was also used to characterize the effect of aging on the PP/Glass specimens. The results showed that the durability of PP/Glass composite is related to the quality of their consolidation. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

The morphing properties of a smart fiber metal laminate

This article investigates the activation characteristics of a novel fiber‐metal laminate (FML) based on a nickel–titanium (Ni–Ti) shape memory alloy. Initial attention focuses on manufacturing this smart FML in which a woven glass fiber reinforced epoxy material is sandwiched between two shape memory alloy (SMA) outer skins. Activation tests on cantilever beams using a hot air gun have shown that the FMLs exhibits a distinct actuation capability in which beam rotations of up to 11° were recorded. An examination of the edges of polished samples indicated that no damage was incurred by the FML during the activation process. The functionality of the FMLs was enhanced through the introduction of embedded electrical resistance wires located between the composite and metal plies. Here, the embedded electrical wires were heated by passing an electric current through them, thereby activating the SMA plies in a more effective and controllable manner. As before, significant beam tip rotations were recorded in the FMLs in a relatively short time period. Finally, polymer‐based optical fiber (POF) and fiber‐bragg grating (FBG) sensors were introduced into the FMLs in order to monitor their deflection during the activation process. The results of these tests showed that such sensing elements can be successfully employed to monitor the actuation response of these layered laminates. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Mechanical properties of carbon nanotube/carbon fiber reinforced thermoplastic polymer composite

Carbon nanotube (CNT)/carbon fiber (CF) hybrid fiber was fabricated by sizing unsized CF tow with a sizing agent containing CNT. The hybrid fiber was used to reinforce a thermoplastic polymer to prepare multiscale composite. The mechanical properties of the multiscale composite were characterized. Compared with the base composite (traditional commercial CF), the multiscale composite reinforced by the CNT/CF hybrid fiber shows increases in interlaminar shear strength (ILSS) and impact toughness. Laminate containing CNTs showed a 115.4% increase in ILSS and 27.0% increase in impact toughness. The reinforcing mechanism was also discussed by observing the impact fracture morphology. POLYM. COMPOS., 38:2001–2008, 2017. © 2015 Society of Plastics Engineers     

Mechanical properties of unidirectional continuous fiber self‐reinforced polyethylene graded laminates

The aim of this study is to prepare of self‐reinforced polyethylene graded composite laminates (SrPEGCL) by adopting both concepts of “graded” and “self‐reinforced” and analyze their mechanical properties under tensile loading. Three different kinds of fiber volume fractions were employed to prepare continuous fiber unidirectional symmetry SrPEGCL with two graded directions. Tensile experiments were carried out to investigate tensile properties of SrPE composites in longitudinal, transverse, and 45‐bias direction. The microscopic failure mechanism of SrPEGCL were studied and observed by Scanning Electron Microscope (SEM). Laminate stress analysis with ply‐by‐ply discount method was adopted to investigate the damage mechanism using failure criteria and parallel spring model. Observations and conclusions about the effect of graded structure and graded direction on mechanical properties of SrPEGCL under tensile loading were discussed. Compared to common self‐reinforced polyethylene composites, SrPEGCL with the same or even less overall fiber volume fraction exhibited 10–20% higher tensile strength under longitudinal, transverse and 45‐bias loading direction, while graded direction had an effect on the mechanical strength of SrPEGCL as well. POLYM. COMPOS., 36:128–137, 2015. © 2014 Society of Plastics Engineers     

Thermal properties of glass fiber reinforced polyamide 6 composites throughout the direct long‐fiber reinforced thermoplastic process

The direct long‐fiber reinforced thermoplastic (D‐LFT) process offers a streamlined material processing technique and decreases the degradation of the material. To ensure product consistency and process optimization, it is imperative to understand how the process sequence affects degradation and thermal properties of the material during the D‐LFT process. This study investigates variation in molecular weight and thermal properties of the glass fiber reinforced polyamide 6 (PA6) composites throughout the D‐LFT process. Viscosity number (VN) measurements, thermogravimetric analyses (TGA), and differential scanning calorimetry (DSC) analyses were performed on samples taken from different locations along the D‐LFT process. It was found that VN, which is a measure of molecular weight of the PA6 base resin, decreased throughout the processes. In contrast, TGA results suggested that apparent activation energy for decomposition increased during consecutive process stages. Non‐isothermal DSC results showed that there were no significant changes to the degree of crystallization; however, isothermal DSC results indicated that later stages of the process showed a decrease in crystallization half‐time, and the largest changes were observed in areas after the two extrusion portions of the process. POLYM. ENG. SCI., 58:46–54, 2018. © 2017 Society of Plastics Engineers     

The effect of processing conditions on the mechanical properties and morphology of self‐reinforced wood‐polymer composite

Highly oriented self‐reinforced round rods were produced from wood‐polymer composite (WPC) by solid‐state extrusion through a conical die. The effects of processing parameters such as draw ratio and die temperature on density, physical properties, and molecular morphology of the rods were systematically investigated. The WPC rods show an increase in density and significant improvements in the tensile properties at higher draw ratio. The tensile strength and modulus reach to 81.6 and 2200 MPa, respectively, at draw ratio of 8. In addition, scanning electron microscopy and wide‐angle X‐ray diffraction were used to observe the morphology of self‐reinforced rods and it was found uniquely fibrous and highly oriented throughout the profiles. POLYM. COMPOS., 34:1567–1574, 2013. © 2013 Society of Plastics Engineers     

Mechanical properties of short fiber reinforced thermoplastic blends

An immiscible thermoplastic component was added to a conventional short fiber reinforced polymer to study its effect on the mechanical properties of the composite. Because of the preferential wetting of the fiber reinforcement a continuous network was formed of fibers ‘welded’ together by the minor component within the matrix polymer.Polyethylene (PE) was used as the matrix, polyamide-6 (PA6) as dispersed polymer phase and glass fibers (GF) as reinforcement. The obtained composite retained unusually high values of the elasticity modulus at temperatures above the melting point of the matrix. The upper limit of the ‘applicability’ of the material is determined by the melting point of the minor component. A simple model was derived to describe the mechanical properties of the composite. The model shows a good agreement with the experimental data. The influence of the model parameters on the predictions of the model was examined.     

Polymer‐based self‐lubricating material

A low‐friction coefficient material with color based on proper selection of polar conditions of pigment and liquid lubricant was developed. Bush‐type bearings were made from poly oxymethylene reinforced with inorganic fillers, including polar compounds of white carbon and glass powder, and nonpolar compounds of carbon black and graphite. The fillers were coated with different levels of titanate, and with polar lubricants such as cetyl alcohol and palmitic acid, and nonpolar lubricants of motor oil, and paraffin. The frictional properties at constant velocity and at constant loading, and the relationships between materials polarity are discussed. An excellent self‐lubricating material of frictional coefficient less than 0.02 was obtained. That is superior to the most current commercial products claiming μ = 0.05 ～ 0.06. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1514–1519, 2001     

Maleic anhydride‐grafted‐polybutadiene as a controlled defibrillating and dispersing agent for short aramid fiber reinforced thermoplastic polyurethane composite with improved mechanical properties

The reinforcing effect of resorcinol formaldehyde latex (RFL) coated short aramid fiber on an ester‐based thermoplastic polyurethane (TPU) was investigated on the basis of mechanical properties. Short fibers having different fiber length were used for the reinforcement. The exceptionally high Young's modulus and low strain modulus indicate the reinforcing effect of this fiber on to the TPU matrix. It has been observed that fibers of 3 mm length at 10 phr loading and 6 mm length even at a loading of 5 phr start to exhibit severe fibrillation: the longitudinal splitting of fiber having larger diameter into thinner fibrils during processing. Fibrillation favorably affects the mechanical bonding with the matrix because of the large surface area as well as surface irregularities provided by the fibrillated fiber. However, fibrillation adversely affects the fiber dispersion by enhancing the fiber aggregation. This leads to a greater disturbance in the strain hardening behavior of the TPU matrix and subsequently reducing the tensile strength and elongation at break especially at high fiber loading. Therefore, to control the degree of fibrillation a pre‐treatment has been applied on the aramid fiber surface with maleic anhydride‐grafted‐polybutadiene (PB‐g‐MA) prior to mixing it with the TPU matrix. A good quality of fiber dispersion with improved tensile strength and elongation at break has been achieved even with 6 mm short fiber at a loading of 10 phr with the treatment of only 5 phr of PB‐g‐MA. The tensile fractured surface morphological analyses of PB‐g‐MA coated fiber filled TPU composite strongly advocate these results. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2205–2216, 2013     

Preparation and properties of polyamide‐6‐based thermoplastic laminate composites by a novel in‐mold polymerization technique

In this work, a method for preparation of polyamide‐6 (PA6) based laminates reinforced by glass fiber‐ (GFL) or polyamide‐66 (PA66) textile structures (PL) via reactive injection molding is disclosed. It is based on in‐mold anionic polymerization of ε‐caprolactam carried out at 165°C in the presence of the respective reinforcements performed in newly developed prototype equipment whose design concept and operation are described. Both composite types were produced for reaction times of 20 min, with conversion degrees of 97–99%. Initial mechanical tests in tension of GFL samples displayed almost twofold increase of the Young's modulus and stress at break values when compared with the neat anionic PA6. The improvement was proportional to the volume fraction V_f of glass fiber fabric that was varied in the 0.16–0.25 range. A 300% growth of the impact strength was registered in PL composites with V_f of PA66 textile of 0.1. Removing the surface finish of the latter was found to be a factor for improving the adhesion at the matrix–fiber interface. The mechanical behavior of GFL and PL composites was discussed in conjunction with the morphology of the samples studied by optical and electron microscopy and the matrix crystalline structure as revealed by synchrotron X‐ray diffraction. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40083.     

The mechanical and fatigue properties of flowable crosslink thermoplastic polymer blends based on self‐catalysis of transesterification

A flowable crosslink polymer blend was successfully developed through a reactive compounding process. An epoxy captained ethylene acrylate copolymer and a carboxylic acid and zinc ion contained ethylene acrylic copolymer were employed to react in a twin screw extruder to form a partially crosslink polymer blend which was flowable at high temperature due to the rapid transesterification catalyzed by the zinc ion in the polymer. The developed crosslink polymer blend showed a significant improvement of the mechanical strength, thermal stability, and fatigue performance compared to the neat ethylene acrylic copolymer because of the strong chemical crosslink among polymer chains. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44964.     

碳纤维增强环氧树脂基复合材料的性能研究

研究了WBS-3环氧树脂固化体系的反应特性,分析了该固化体系浇铸体的性能;并以碳纤维(T-700S)为增强材料,采用手糊成型螺栓加压工艺制备了WBS-3/T-700S复合材料,研究了复合材料的常温力学性能、高温力学性能、水煮后力学性能和动态力学性能,并对弯曲断面进行分析。研究结果表明,WBS-3树脂基体黏度低、适用期长且韧性好,适合于手糊成型、缠绕成型等低成本制造工艺;由此制得的WBS-3/T-700S复合材料具有优良的力学性能和耐高温性能,其弯曲强度为1434MPa,拉伸强度为1972MPa,剪切强度为76.1MPa,玻璃化温度(Tg)超过210℃;该WBS-3/T-700S复合材料具有很好的界面粘接性(树脂对纤维的浸润性良好)、较低的空隙率且纤维分布均匀。     

Mechanical properties of glass fiber/organic fiber mixed–mat reinforced thermoplastic composites

The purpose of this study is to investigate the influence of different types of fibers on the mechanical properties of hybrid composite materials. Long and short glass fibers (GF) and different types of organic fibers, viz. aramid fiber, DuPont Kevlar‐49 (KF), liquid crystalline polymer (LCP), and vinylon (VF) in hybrid composites, were used to reinforced the high density polyethylene (HDPE) matrix. The long fiber hybrid composites were prepared in a “fiber separating and flying machine,” while the short fiber hybrid composites were prepared in an “elastic extruder.” The total amount of fibers used in both long and short fiber hybrid composites was fixed at 20 vol%. The influence of fiber content, length, and mixing ratio on mechanical properties, such as tensile, bending, Izod and high rate impact strength, as well as viscoelastic propertics in the solid state, was studied. Fracture surfaces of the materials were also examined using a scanning electron microscopy.     

Rheological and mechanical behavior of long‐polymer‐fiber reinforced thermoplastic pellets

Polymer–polymer materials consist of a thermoplastic matrix and a thermoplastic reinforcement. Recent research activities concentrate on the manufacturing of semi‐finished polymer–polymer materials in other shapes than the commercially available tapes and sheets. In particular, a pellet‐like form provides the possibility of processing the polymer–polymer material by injection and compression molding. Nevertheless, the thermoplastic reinforcement is vulnerable to excessive heat and the processing usually needs special attention. The current study investigates the processing of long‐polymer‐fiber reinforced thermoplastic pellets, namely polypropylene‐polyethylene terephthalate and a single‐polymer polyethylene terephthalate, by extrusion for subsequent compression molding applications. The flow characteristics of the material as well as the preservation of the polymer reinforcement can be handled by accurate temperature control. The tensile and impact properties decrease with increasing process temperature though. Moreover, the results prove that the use of a common long‐fiber reinforced thermoplastic process chain is applicable to the newly developed polymer–polymer material. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39716.     

Preparation and properties of thermoplastic starch‐polyester laminate sheets by coextrusion

The effects of extrusion and formulation variables on the structure and properties of starch‐polyester laminates were examined. Three‐layer polyester/starch/polyester sheets were prepared using a twin‐screw extruder for the starch/water center layer, a single screw extruder for the outer polyester layers and a feedblock and coathanger type sheet die. Overall sheet and coating thicknesses were more uniform as coating polymer (poly(ε‐caprolactone), PCL) viscosity decreased (lower molecular weight), starch melt viscosity increased (lower moisture) and feedblock/die temperature increased. Peel strengths were 1 to 2 orders of magnitude larger for high than low molecular weight PCL. High peel strengths were associated with rough, wavy interfaces (interfacial instability). Addition of plasticizer such as glycerol and sorbitol to the starch decreased peel strengths. Peel strengths varied little with type of polyester coating, except, perhaps, for polylactic acid and polyesteramide, which were more difficult to peel. Some possible applications of laminated starch sheets include food packaging and controlled release of drugs, pesticides, insect diets, etc.     

Polypropylene composites obtained from self‐reinforced hybrid fiber system

The purpose of the study was to obtain a composite material with the self‐reinforced structure, which processing provide increased mechanical properties. The composites used in presented work were prepared from the two types of fiber mixtures, both were based on polypropylene fibers, the difference was in used cellulose or wood flour filler. Composites were prepared using the hot compaction method. The presented research describes the effect of the composite composition and processing conditions. The results include the static tension measurements, tensile impact tests and thermal analysis, including: DSC and DMTA. The structure has been studies using the SEM observations. Results of presented studies confirm the self‐reinforcing effect in obtained hybrid composites. It provides in the comparison to the standard wood polymer composites to the higher level of material reinforcement with lower amount of natural filler. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43283.     

Consolidation of net‐shape random fiber thermoplastic composite preforms

A novel thermoplastic composite preforming process has been developed. This thermoplastic programmable powdered preforming process (TP‐P4) uses commingled glass and polypropylene yarns, which are chopped to a desired length and deposited onto a vacuum screen. The as‐placed fibers are then heat‐set for improved handling, before potential preconsolidation, and final conversion with preheating and press forming. This work investigated the effect of using either a double belt lamination preconsolidation stage or using an improved heat‐setting stage. Polymer degradation was examined using gel permeation chromatography analysis, and the void content evolution tracked using image analysis techniques from the heat setting stage until the final part. It was shown that without preconsolidation, preforms prepared for a 2 mm thick final pressed part could be compression molded into a substantially void free, non degraded part. By using the lamination route, this limit could be increased to 4 mm, but without allowing local thickness changes in the preform. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Aramid‐short‐fiber reinforced rubber as a tire tread composite

Mechanical and dynamic‐mechanical properties of a typical tire tread compound reinforced with one part aramid short fibers were investigated in order to predict the effects of fibers on tire tread performances such as rolling resistance and traction. Rubber processing, including mixing and extrusion, was performed in an industrial scale. Fiber orientation as a result of extrusion was evaluated quantitatively and qualitatively using mechanical anisotropy in swelling and scanning electron microscopy, respectively. Unidirectional tensile tests revealed higher modulus, but slightly lower strength and elongation at break for the composites stretched in the longitudinal (orientation) and transverse directions than those for the isotropic reference compound with no fiber. Dynamic mechanical thermal analysis showed that relative values of loss factor for the longitudinal and transverse composites and the reference compound depended on the state of polymer as glassy or rubbery. Therefore, a high loss factor at lower temperatures and a low loss factor at higher temperatures predicted a balanced improvement of tire traction and rolling resistance as a result of fiber addition. Heat build‐up and abrasion experiments showed that addition of fiber did not deteriorate other performances of tire tread. Also, the fibers had negligible effects on processing and vulcanization characteristics of the composite. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Addition‐cure‐type phenolic resin based on alder‐ene reaction: Synthesis and laminate composite properties

A maleimide‐functional phenolic resin was reactively blended with an allyl‐functional novolac in varying proportions. The two polymers were coreacted by an addition mechanism through Alder‐ene and Wagner–Jauregg reactions to form a crosslinked network system. The cure characterization was done by differential scanning calorimetry and dynamic mechanical analysis. The system underwent a multistep curing process over a temperature range of 110–270°C. Although the cure profiles were independent of the composition, the presence of maleimide led to a reduced isothermal gel time of the blend. Increasing the allylphenol content decreased the crosslinking in the cured matrix, leading to enhanced toughness and improved resin‐dominant mechanical properties of the resultant silica laminate composites. Changing the reinforcement from silica to glass resulted in further amelioration of the resin‐reinforcement interaction, but the resin‐dominant properties of the composite remained unaltered. Increasing the maleimide content resulted in enhanced thermal stability. Integrating both the reactive groups in a single polymer and its curing led to enhanced thermal stability and T_g, but to decreased mechanical properties of the laminate composites. This can be attributed to a brittle matrix resulting from enhanced crosslinking facilitated by interaction of the reactive groups located on the polymer of an identical backbone structure. The cured polymers showed a T_g in the range of 170–190°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 737–749, 2001