Durability of glass‐fiber‐reinforced polymer composites in an alkaline environment

This study investigated the aging of urethane and urethane‐modified vinyl ester (UMVE) GFRPs (glass fiber reinforced polymers) when they were exposed to alkaline solution for six months under a sustained load of 34.5 MPa or 16–20% of their tensile strength. The second experiment exposed both types of GFRP to alkaline solution without load for 6 months. The final experiment determined the alkaline solution diffusion coefficients into GFRP and neat polymer resin samples by measuring the change in mass of each sample as a function of time. After the GFRP samples were aged for 6 months, their tensile strengths were measured and compared with that of non‐aged samples to determine the aging effect. It was found that alkaline solution alone without sustained load did not significantly reduce or change the tensile strength of any GFRP sample. However, the presence of sustained load greatly increased the aging effect, particularly more for urethane GFRP than on UMVE GFRP. Urethane GFRP experienced a tensile strength reduction of 57.5%, while UMVE GFRP lost 27.3% of its original tensile strength. J. VINYL ADDIT. TECHNOL., 13:221–228, 2007. © 2007 Society of Plastics Engineers     

Flexural behavior of methyl methacrylate modified unsaturated polyester polymer concrete beams reinforced with glass‐fiber‐reinforced polymer sheets

This study represents the behavior of flexural test of methyl methacrylate modified unsaturated polyester polymer concrete beam reinforced with glass‐fiber‐reinforced polymer (GFRP) sheets. The failure mode, load–deflection, ductility index, and separation load predictions according to the GFRP reinforcement thickness were tested and analyzed. The failure mode was found to occur at the bonded surface of the specimen with 10 layers of GFRP reinforcement. For the load–deflection curve, as the reinforcement thickness of the GFRP sheet increased, the crack load and ultimate load greatly increased, and the ductility index was found to be the highest for the beam with the thickness of the GFRP sheet at 10 layers (6 mm) or 13 layers (7.3 mm). The calculated results of separation load were found to match only the experimental results of the specimens where debonding occurred. The reinforcement effect was found to be most excellent in the polymer concrete with 10 layers of GFRP sheet reinforcement. The appropriate reinforcement ratio for the GFRP concrete beam suggested by this study was a fiber‐reinforced‐plastic cross‐sectional ratio of 0.007–0.008 for a polymer concrete cross‐sectional ratio of 1 (width) : 1.5 (depth). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fatigue characteristics of a glass‐fiber‐reinforced polyamide

This paper deals with prediction of the temperature rise in the stress‐controlled fatigue process of a glass‐fiber‐reinforced polyamide and the application of a temperature and frequency superposition procedure to the S‐N curve. An experimental equation was derived to predict the temperature rise from calculations based on the fatigue test conditions and viscoelastic properties of the material. The temperature rise (ΔT) can be expressed as a product of a coefficient term Φ(L, κ) concerning heat radiation and the test‐specimen shape and a function term P_fat concerning the viscoelastic properties and fatigue test conditions. Φ(L, κ) was found experimentally to derive the equation for predicting the temperature rise blow or above the glass transition temperature (T_g) of the material. The equation σ_R = −S_Tf A log N_fR + S_Tf B was obtained as a procedure for applying temperature and frequency superposition to S‐N curves in consideration of ΔT. This procedure was obtained by combining both temperature‐ and frequency‐superposition techniques. Here, σ_R and log N_fR represents the stress and the fatigue lifetime calculated at a given temperature and frequency, A and B denote the slope and intercept of any arbitrarily chosen S‐N curve, and S_Tf is a shift factor for temperature and frequency superposition. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1783–1793, 1999     

Creep behavior of glass‐fiber‐reinforced nylon 6 products

The creep properties, that is, the velocity constant, activation energy, stress index, and time index, of a test piece (TP) cut from a glass‐fiber‐reinforced nylon 6 product were successfully determined by a compression creep test. In the determination of the creep properties, the experimental creep curves for the TP were fitted by finite element analysis (FEA). Fiber‐reinforced nylon 6 beams with different fiber orientations were also prepared, and their creep properties were successfully determined by a combination of the bending creep test and the corresponding analysis. The creep behavior of the press‐fit component composed of a metal collar and a fiber‐reinforced nylon 6 product was predicted by FEA with the determined creep properties of the TP. The predicted retention forces were in good agreement with the experimental ones. The effects of the fiber orientation on the long‐term reliability of the press‐fit component are also discussed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Experimental investigation of moisture diffusion in short‐glass‐fiber‐reinforced polyamide 6,6

Moisture diffusion in polyamide 6,6 (PA66) and its short glass fiber‐reinforced composites has a great influence on their mechanical properties and service lives under hydrothermal environments. Hence, the moisture diffusion in neat PA66 and its composites was studied comprehensively in this study with the general Fickian model. To systematically investigate the effects of the fiber content, humidity, temperature, and humidity–temperature coupling effect on the diffusion coefficient and equilibrium concentration, gravimetric experiments for the PA66 composites were carried out under different hydrothermal conditions. The results show that the equilibrium moisture concentration depended on the relative humidity and fiber content but only depended weakly on temperature. The diffusion velocity was affected by the three aforementioned factors with different trends. The analysis of variance demonstrated that the humidity–temperature coupling effect played an important role in the diffusion process. The regression analysis gave the corresponding quadratic regression equations. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42369.     

Fabrication and properties of nano‐ZnO/glass‐fiber‐reinforced polypropylene composites

Polypropylene (PP) is widely used in many fields, such as automobiles, medical devices, office equipment, pipe, and architecture. However, its high brittle transformation temperature, low mechanical strength, dyeing properties, antistatic properties, and poor impact resistance, considerably limit its further applications. Nano‐ZnO treated by KH550 coupling agent and glass fibers (GFs) were introduced in order to improve the mechanical performance and flowability of PP in this research. The crystallization behavior and microstructure of nano‐ZnO/GFs/PP hybrid composites were analyzed by differential scanning calorimetry, transmission electron microscopy, and scanning electron microscopy. The effect of crystallization behavior on the mechanical properties of the nanocomposites was investigated and analyzed. The results indicated that nano‐ZnO surface‐coupled by KH550 could be uniformly dispersed in the PP matrix. The incorporation of nano‐ZnO and GFs resulted in increases of the crystallization temperature and crystallization rate of PP and a decrease of the crystallization degree. The introduction of nano‐ZnO and GFs also enhanced the tensile strength and impact toughness of the hybrid composites and improved their fluidity. Composites containing 2% of nano‐ZnO and 40% of GFs possessed the optimum mechanical properties. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

A phosphorus‐containing inorganic compound as an effective flame retardant for glass‐fiber‐reinforced polyamide 6

A novel inorganic compound, aluminum hypophosphite (AP), was synthesized successfully and applied as a flame retardant to glass‐fiber‐reinforced polyamide 6 (GF–PA6). The thermal stability and burning behaviors of the GF–PA6 samples containing AP (flame‐retardant GF–PA6) were investigated by thermogravimetric analysis, vertical burning testing (with a UL‐94 instrument), limiting oxygen index (LOI) testing, and cone calorimeter testing (CCT). The thermogravimetric data indicated that the addition of AP decreased the onset decomposition temperatures, the maximum mass loss rate (MLR), and the maximum‐rate decomposition temperature of GF–PA6 and increased the residue chars of the samples. Compared with the neat GF–PA6, the AP‐containing GF–PA6 samples had obviously improved flame retardancy: the LOI value increased from 22.5 to 30.1, and the UL‐94 rating went from no rating to V‐0 (1.6 mm) when the AP content increased from 0 to 25 wt % in GF–PA6. The results of CCT reveal that the heat release rate, total heat release, and MLR of the AP‐containing GF–PA6 samples were lower than those of GF–PA6. Furthermore, the higher additive amount of AP affected the mechanical properties of GF–PA6, but they remained acceptable. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Improved thermal properties of jute fiber‐reinforced polyethylene nanocomposites

The thermal behavior of chemically modified jute fiber‐reinforced polyethylene (PE) nanocomposites was investigated. Nanocomposites were prepared by hot press molding technique using different fiber loadings (5, 10, 15, and 20 wt%) for both treated and untreated fibers. Jute fibers were chemically modified with benzene diazonium salt to increase their compatibility with the PE matrix. Surface and thermal properties were subsequently characterized. Fourier transform infrared spectroscopy and scanning electron microscopy analysis were used to study the surface morphology. Thermogravimetric analysis (TGA) and differential scanning calorimetry were carried out for thermal characterization. Fourier transform infrared spectroscopy and scanning electron microscopy study showed interfacial interaction among jute fiber, PE, and nanoclay. It was observed that, at optimum fiber content (15 wt%), treated jute fiber‐reinforced composites showed better thermal properties compared with that of untreated ones and also that nanoclay‐incorporated composites showed enhanced higher thermal properties compared with those without nanoclay. POLYM. COMPOS., 38:1266–1272, 2017. © 2015 Society of Plastics Engineers     

Experimental investigation of acid environment influences on load‐bearing performance of pin‐connected continuous glass‐fiber‐reinforced polyphenylenesulfide composites

In this study we aimed to investigate the load‐bearing performance of pinned connections in corrosive environment. Experimental results are presented for the effect of acid environment on load‐bearing performance of pin‐connected continuous glass‐fiber‐reinforced polyphenylenesulfide composites. Chemical corrosion was also observed as an important environmental factor which affected the load‐bearing performance remarkably. Specimens were exposed to hydrochloric acid in order to find the durability of glass‐fiber‐reinforced plastics in hostile environments. An attempt is made to explain this phenomenon. The failure formation of material was affected by exposure time to HCl. Consequently, after the material has been exposed to acidic environment for 16 weeks, there were ∼93 and 95% performance decrease in the final failure load and first failure load, respectively. POLYM. COMPOS., 2010. © 2008 Society of Plastics Engineers     

Joining of fiber‐reinforced polymer tubes for high‐pressure applications

Fiber‐reinforced polymer composites offer superior performance particularly in harsh environments; hence, they are recognized as an attractive material, especially for the transportation of pressurized fluids. However, an extensive use of these composites has been hampered, in part due to unsatisfactory solutions for the joining of subcomponents, and insufficient knowledge on the associated damage behavior. A favorable connection design for a piping system can be an adhesively bonded joint. In this study, a unique adhesive injection technique is presented that joins composite pipe sections using filament‐wound overlap sleeve couplers. The purpose of the present study was to characterize the performance and associated damage behavior of a prototype‐size pipe structure joined by the above procedure. Internal pressure and axial traction were applied to specimens at various biaxial ratios. In addition to the experimental investigation, the joint geometry was also modeled numerically employing the finite element technique. This yielded a better understanding of the damage behavior and enabled a parametric study that provided recommendations for an improved joint design. POLYM. COMPOS., 27:99–109, 2006. © 2005 Society of Plastics Engineers     

Thermal polymerization of a brominated flame retardant in a glass‐fiber‐reinforced polypropylene—quantitative analysis

Pentabromobenzylacrylate (PBBA) is a possible candidate for use as a fire retardant (FR) in polypropylene (PP) composites. While PBBA imparts FR properties to the PP composite, it also affects adversely its mechanical properties. The FR may undergo thermal polymerization or grafting to the PP chains during processing. To study the effect of the different forms of FR (monomer, polymerized, or grafted) on composite properties, we have quantified the extent of FR polymerization and extent of grafting onto the PP chains. Fourier transform infrared microscopy was used in this work to determine the extent of polymerization and the spatial distribution of the FR. The latter was found to be homogeneous throughout the composite. Thermal polymerization of the FR during extrusion is varied mainly by the addition of an antioxidant. The grafting process of the FR onto PP depends on the degree of thermal polymerization, and therefore on the addition of antioxidant. The limiting value for grafting achieved at full polymerization is ～10% w/w. The grafted FR was found to have a significant effect on PP crystallinity, and hence it is expected to affect the mechanical properties as well. Bromine analysis indicates the FR has reacted with filler surfaces as well. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1506–1515, 2003     

Crystallization of glass fiber‐reinforced poly(p‐phenylene sulfide) nanocomposites

Ternary composites of glass fiber‐reinforced poly(p‐phenylene sulfide) (PPS/GF) filled with nanometric calcium carbonate (nano‐CaCO₃) were prepared by means of a twin‐screw extruder. The nano‐CaCO₃ surface was treated with stearate and treated with titanate, the composites being called SI composite system and SII composite system, respectively. The crystallization and heatproof properties of the PPS/GF/nano‐CaCO₃ composites were measured using a differential scanning calorimeter, to investigate the influence of the nanometric filler content on the crystallinity. The results show that the variation of the starting crystallization temperature, crystallization temperature and crystallinity with an increase of the particle weigh fraction (?_f) of SI composite system is different from that of SII composite system. When ?_f is less than 4 wt%, the crystallinity of the two composite systems increases and then decreases slightly with increasing ?_f. Moreover, the crystallization behavior and mechanisms are discussed. Copyright © 2011 Society of Chemical Industry     

Visual analysis of plastication of long‐glass fiber‐reinforced resins using a glass‐insert heating cylinder

The fiber‐reinforced plastication processes during the injection molding of reinforced resins with long fibers are difficult to observe through visualization cylinders because of possible obstacles, such as (1) opacification of melts, (2) abrasion on the inner surface of glass windows, and (3) breakage of glass windows under high pressures. In this study, we visualized the plastication process of long‐glass fiber‐reinforced resins containing 50 wt% fibers. In plastication experiments using three full‐flight screws with different compression ratios, we observed the instability of the melting process, the generation of solid beds and melt pools, and the breakup of melted segments. We demonstrated that the plastication process depends considerably on the compression ratio and clarified the characteristic molding phenomena related to fiber breakup. Based on our observations, we proposed a model that explains the different fiber breakage distributions at different compression ratios during the melting process of long‐glass fiber‐reinforced resins. POLYM. ENG. SCI., 59:1300–1309 2019. © 2019 Society of Plastics Engineers     

Fiber breakage and dispersion in carbon‐fiber‐reinforced nylon 6/clay nanocomposites

In this paper, short carbon‐fiber‐reinforced nylon 6/clay nanocomposites are prepared via melt compounding, and fiber breakage and dispersion during processing are studied. The influences of clay and processing conditions on fiber breakage and dispersion are taken into consideration. It is found that the presence of organoclay can improve fiber dispersion, which is due to dispersion at the nanoscale of exfoliated clay sheets with large aspect ratio. The bimodal distribution of fiber length is observed in fiber‐reinforced nanocomposites, which is similar to that in conventional fiber‐reinforced composites. The improvement of fiber breakage at moderate organoclay loadings is also observed, which is ascribed to the rheological and lubricating effects induced by organoclay. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Fluorinated and oxyfluorinated short Kevlar fiber‐reinforced ethylene propylene polymer

The thermomechanical behavior of fluorinated and oxyfluorinated Kevlar fiber‐reinforced ethylene propylene (EP) composites has been studied. The composites have been prepared using brabender mixer and are cured using compression molding technique. FTIR study has been performed to understand the chemical reaction occurred due to modification of composites. Thermal behavior and crystallinity have been studied by DSC, TGA, DMTA, and XRD. These studies show that thermal stability, storage modulus, as well as crystallinity of the treated Kevlar fiber‐reinforced EP increases in comparison to the untreated derivative because the surface‐modified Kevlar fiber results in good adhesion between the fiber surface and EP matrix. Tensile strength increases in case of treated Kevlar fiber‐reinforced EP in comparison to the untreated one. SEM study supports all the above results. AFM results show that surface roughness increases because of the surface modification resulting from the incorporation of functional group‐induced Kevlar fiber. Polym. Compos. 27:205–212, 2006. © 2006 Society of Plastics Engineers     

Tensile behavior of glass‐fiber‐filled polyacetal: Influence of the functional groups of polymer matrices

We investigated the tensile behavior of glass‐fiber‐filled polyacetal [i.e., polyoxymethylene (POM)], focusing on the mutual influence of the functional groups in the POM matrices and the glass binder system. The different POM matrices were compounded with three kinds of glass fibers (20 wt %) treated with different glass binders, namely, epoxy resin, thermoplastic polyurethane (TPU), and a mixture of TPU and epoxy resin. A good correlation between the tensile strength and elongation at break was observed, regardless of the difference in the glass binders. The composites based on the modified POM matrix, which had both a carboxyl end group and a hydroxyl end group, improved the tensile properties noticeably in comparison with those based on the normal POM matrix. The composites were strengthened with an increase in the concentration of the functional groups. The results of scanning electron microscopy observations indicated that the fractured surfaces of a specimen having maximum tensile strength and elongation exhibited cohesion of the modified POM on the surfaces of the glass fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Visualization analysis of reciprocating‐screw plastication process of glass fiber‐reinforced resins in a glass‐inserted heating cylinder

One challenge in injection molding of long fiber‐reinforced resins is minimizing the fiber breakage during resin plastication and resin flow into a mold. Such fiber breakage reduces the strength of the molded product. Reciprocating plastication is subjected to periodic positional fluctuations of the screw and cylinder in the molding cycle. In this study, visualization experiments were conducted on the reciprocating plastication of long glass fiber (GF)‐reinforced polypropylene with 50 wt% GF. It was found that: (1) temporary voids form in the resin during the metering process, and the pellets rotate from an orthogonal to parallel orientation in the flight direction; (2) length of the weight‐averaged fiber temporarily decreased in the middle stage of the injection process; (3) length of the weight‐averaged fiber was most strongly influenced by the waiting time; and (4) for constant waiting time, the fiber breakage could be minimized by lowering the rotation speed, lowering the back pressure, and shortening the charge stroke. POLYM. ENG. SCI., 59:846–853, 2019. © 2018 Society of Plastics Engineers     

Short‐term flexural creep behavior and model analysis of a glass‐fiber‐reinforced thermoplastic composite leaf spring

Present work investigated the short‐term flexural creep performance of fiber reinforced thermoplastic injection molded leaf springs. Unreinforced polypropylene, 20 wt % short and 20 wt % long glass fiber reinforced polypropylene materials were injection‐molded into constant thickness varying width mono leaf spring. Short‐term flexural creep tests were performed on molded leaf springs at various stress levels with the aid of in‐house developed fixture integrated with the servo‐hydraulic fatigue machine. Spring rate reduction is reported as an index for the accumulated damage. Experimental creep performance of molded leaf springs for 2 h was utilized to predict the creep performance with the aid of four parameter HRZ model and compared with 24‐h experimental creep data. Test results revealed that HRZ model is sufficient enough to predict short‐time flexural creep performance of engineering products over wide range of stress. Test results also confirmed the suitability of long fiber reinforced thermoplastic material for creep application over other considered materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Modeling and simulation of fiber‐reinforced polymer mold‐filling with phase change

A gas‐solid‐liquid three‐phase model for the simulation of fiber‐reinforced composites mold‐filling with phase change is established. The influence of fluid flow on the fibers is described by Newton's law of motion, and the influence of fibers on fluid flow is described by the momentum exchange source term in the model. A revised enthalpy method that can be used for both the melt and air in the mold cavity is proposed to describe the phase change during the mold‐filling. The finite‐volume method on a non‐staggered grid coupled with a level set method for viscoelastic‐Newtonian fluid flow is used to solve the model. The “frozen skin” layers are simulated successfully. Information regarding the fiber transformation and orientation is obtained in the mold‐filling process. The results show that fibers in the cavity are divided into five layers during the mold‐filling process, which is in accordance with experimental studies. Fibers have disturbance on these physical quantities, and the disturbance increases as the slenderness ratio increases. During mold‐filling process with two injection inlets, fiber orientation around the weld line area is in accordance with the experimental results. At the same time, single fiber's trajectory in the cavity, and physical quantities such as velocity, pressure, temperature, and stresses distributions in the cavity at end of mold‐filling process are also obtained. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42881.     

Mechanical properties and processibilty of glass‐fiber‐, wollastonite‐, and fluoro‐rubber‐reinforced silicone rubber composites

The reinforcement of silicone rubber (SR) imparted by different types of fillers was investigated. Glass fiber (GF), wollastonite and fluoro rubber (FR) as nontraditional filler for rubber were compounded SR and mechanical properties of the prepared composites were evaluated. The addition of silane pretreated GF and wollastonite into SR, tensile strength, abrasion resistance and tear strength of the composites improved considerably. The improvement in the properties was assigned to an increased interaction between the filler and the polymer matrix. For the SR/FR composites system, the elongation at break was increase with increasing concentrations of FR due to sponge like structure resulting from poor compatibility between the two components. To investigate the production potential of extrusion processing method, prepared composites were extruded in a rod type sample. During the curing stage, GF, wollastonite and FR lead to the formation of void in the matrix resin. When GF and wollastonite were treated with silane, the void formations were reduced significantly. The silane treatment process improves not only mechanical strength but also processibility of SR composites in dry conditions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007