Mechanical properties of pineapple leaf fiber-reinforced polyester composites

Pineapple leaf fiber (PALF) which is rich in cellulose, relatively inexpensive, and abundantly available has the potential for polymer reinforcement. The present study investigated the tensile, flexural, and impact behavior of PALF-reinforced polyester composites as a function of fiber loading, fiber length, and fiber surface modification. The tensile strength and Young's modulus of the composites were found to increase with fiber content in accordance with the rule of mixtures. The elongation at break of the composites exhibits an increase by the introduction of fiber. The mechanical properties are optimum at a fiber length of 30 mm. The flexural stiffness and flexural strength of the composites with a 30% fiber weight fraction are 2.76 GPa and 80.2 MPa, respectively. The specific flexural stiffness of the composite is about 2.3 times greater than that of neat polyester resin. The work of fracture (impact strength) of the composite with 30% fiber content was found to be 24 kJ m⁻². Significant improvement in the tensile strength was observed for composites with silane A172-treated fibers. Scanning electron microscopic studies were carried out to understand the fiber-matrix adhesion, fiber breakage, and failure topography. The PALF polyester composites possess superior mechanical properties compared to other cellulose-based natural fiber composites. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1739–1748, 1997     

Mechanical properties of ultrahigh-molecular-weight polyethylene fiber-reinforced PE composites

Three types of high-strength polyethylene (PE) fiber-reinforced composite sheets were made by compression molding at the vicinity of melting point of the fiber. Sheet I was molded from only PE fibers. Sheets II and III were prepared by the compression molding of PE fiber with conventional high- and low-density polyethylene films, respectively. The mechanical properties, thermal behavior, and morphologies of the sheets have been investigated and compared with each other. The tensile strength and elastic modulus of sheet III are 660 MPa and 14 GPa, respectively, which were 60 and 30 times higher than those of typical low-density PE film. Although the elastic modulus of sheet III is 6 GPa less than that of sheet II, the tensile strength of 660 MPa is highest in the three types of sheets prepared in this study. The mechanical properties of sheets II and III were about half of predicted theoretical ones. It was concluded that the interfacial adhesion between PE fiber and PE matrix was an important factor to improve the mechanical properties of this PE sheet. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1431–1439, 1998     

Mechanical properties of continuous bamboo fiber-reinforced biobased polyamide 11 composites

This study is devoted to the analysis of the properties of continuous bamboo fiber (BF)-reinforced polyamide 11 (PA 11) composites. The SEM observations highlighted continuity between BFs and the polymeric matrix showing a high density of hydrogen bonds. The comparative calorimetric study of the matrix and its composites showed that the crystallinity of PA 11 was not modified by the presence of bamboo fibers. The physical aging observed in PA 11 is no more observed in composites due to physical interactions between PA 11 and BFs. The mechanical properties were investigated by tensile strength and dynamic mechanical analysis. The introduction of BFs enhanced Young's modulus of the matrix by a factor of 10. The presence of BFs also improved the storage shear modulus G′ over the whole temperature range. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47623.     

Technological properties of celsian reinforced glass matrix composites

Monoclinic celsian derived from an innovative route, i.e. cation exchanged zeolites heat-treated at low temperature, was added at different contents (10, 20, 30 wt%) to a glass matrix, in order to improve its mechanical and electrical performances. The effect of the celsian reinforcement was evaluated by testing several properties of the composite materials, such as the elastic modulus, abrasion resistance, flexural strength and electrical insulation. The results so far obtained suggest that the addition of the monoclinic celsian to the glass matrix may produce low-cost particulate composites with interesting technological properties.     

Enhanced high-temperature dielectric and microwave absorption properties of SiC fiber-reinforced oxide matrix composites

Because of outstanding performances of the SiC fiber-reinforced ceramic matrix composites in aircraft/aerospace systems, two silicon carbide fiber-reinforced oxide matrices (SiC_f/oxides) composites have been prepared by a precursor infiltration and sintering method. Results indicate that the flexural strength of the SiC_f/Al₂O₃–SiO₂ composite reaches 159 MPa, whereas that of the SiC_f/Al₂O₃ composite is only 50 MPa. The high-temperature microwave absorption properties of the composite are significantly enhanced due to choosing Al₂O₃ and SiO₂ as the hybrid matrices. Particularly, the minimum reflection loss (RL) value of the SiC_f/Al₂O₃–SiO₂ composite reaches −37 dB in the temperature of 200 °C at 8.6 GHz, and the effective absorption bandwidth (RL ≤ −5 dB) is 4.2 GHz (8.2–12.4 GHz) below 400 °C. The superior microwave absorption properties at high temperatures indicate that the SiC_f/Al₂O₃–SiO₂ composite has promising applications in civil and military areas. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47097.     

Mechanical and biodegradation properties of bamboo fiber-reinforced starch/polypropylene biodegradable composites

Bamboo fiber (BF)-reinforced starch/polypropylene (PP) composites were prepared by extrusion and injection molding methods. The mechanical and thermal properties and water absorption were evaluated by different methods. Moreover, composite samples were subjected to biodegradation through soil burial test and microbes medium degradation. Different stages of biodegradation were investigated by weight loss, attenuated total reflection Fourier transformed infrared spectroscopy, differential scanning calorimeter, and scanning electron microscope. It was found that contents of BF and starch resin had a significant influence on the properties of the composites. With more content of BF, the composite exhibited a better flexural property and biodegradation. A distinct decrease of weight loss and mechanical properties indicated the degradation caused by the microbes. After biodegradation, thermal stability of the composites decreased while the crystallinity of PP increased. The results prove that the composites more easily tend to be degraded and assimilated by microbes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48694.     

Mechanical properties of carbon nanofiber/fiber-reinforced hierarchical polymer composites manufactured with multiscale-reinforcement fabrics

Hierarchical polymer composites – defined as carbon nanofiber/fiber-reinforced polymer composites – were manufactured using multiscale-reinforcement fabrics (MRFs) and they were characterized for their mechanical properties. The MRFs were fabricated by electrophoretic deposition of carboxylic acid- or amine-functionalized carbon nanofibers (CNFs) on the surface of sized or unsized carbon fiber layers. Compared to the base composite (not containing CNFs), the hierarchical composites containing the functionalized CNFs showed an increase in interlaminar shear strength (ILSS) and compressive strength. Panels containing amine-functionalized CNFs had the highest increase in properties: 12% in ILSS and 13% in compressive strength. The reinforcement mechanism was also investigated with emphasis placed on the fiber/matrix interface and the load transfer between matrix, CNFs, and carbon fiber.     

Tensile properties of short sisal fiber-reinforced polyethylene composites

Sisal fibers (Agave-Veracruz) have been used as reinforcements in low-density polyethylene (LDPE). The influence of the processing method and the effect of fiber content, fiber length, and orientation on tensile properties of the composites have been evaluated. The fiber damage that normally occurs during blending of fiber and polyethylene by the meltmixing method is avoided by adopting a solution-mixing procedure. The tensile properties of the composites thus prepared show a gradual increase with fiber content. The properties also increased with fiber length, to a maximum at a fiber length of about 6 mm. Unidirectional alignment of the short fibers achieved by an extrusion process enhanced the tensile strength and modulus of the composites along the axis of fiber alignment by more than twofold compared to randomly oriented fiber composites. © 1993 John Wiley & Sons, Inc.     

Mechanical properties in multidimensional composites

The mechanical properties of three dimensional stitched composites were compared against those of the traditional two dimensional laminates. An attempt was made to correlate the change in properties to the change in the third directional fiber density. Tests conducted were the impact, three-point bending, damage tolerance, end notched flexure, and bending fatigue test. The results of these tests show that the third directional fibers can effectively inhibit delamination by increasing the interlaminar shear strength. Three dimensional composites also possess better damage tolerance, fracture toughness, and fatigue life. However, a high stitching density can degrade the in-plane properties of the composites.     

玄武岩纤维增强聚乳酸力学性能及耐老化性能

通过拉伸实验和老化实验，研究了玄武岩纤维含量对BF/PLA拉伸性能、抗冲击性能及耐老化性能的影响规律，通过DSC实验得到BF/PLA复合材料的结晶度，分析其耐老化原因。随着质量分数增加，其拉伸强度增加可达到141 MPa，弹性模量达到5 GPa，达到峰值后又减小。质量分数达到30%时，缺口冲击强度和非缺口冲击强度分别达到6.7 kJ/m²和20.76 kJ/m²。DSC实验结果表明，随着玄武岩纤维含量的增加，聚乳酸复合材料的结晶度由34.6%增加到54.6%，而结晶度的增加可以减缓聚乳酸的降解速度。当质量分数达到60%时，老化实验后的弹性模量可以保持降解前的77%，延缓降解速度较为明显。经分析，拉伸强度与玄武岩纤维质量分数呈二次多项式关系，而弹性模量与玄武岩纤维质量分数之间呈线性关系。这种函数关系不受材料力学性能下降的影响。     

长玻璃纤维增强尼龙6复合材料力学性能的研究

研究以聚丙烯接枝马来酸酐(PP-g-MAH)和聚烯烃弹性体接枝马来酸酐(POE-g-MAH)为界面相容剂的长玻璃纤维增强尼龙6(LGF/PA 6)复合材料的力学性能,并与短玻璃纤维增强尼龙6(SGF/PA 6)复合材料的力学性能进行对比。结果表明:LGF/PA 6复合材料的拉伸强度、弯曲强度和弯曲模量均随着玻璃纤维含量的增加呈直线上升趋势,玻璃纤维质量分数达到40%时,增强效果十分显著;在添加相同含量的玻璃纤维时,LGF/PA 6复合材料的拉伸强度、弯曲强度、弯曲模量低于SGF/PA 6复合材料;2种复合材料的冲击强度均随着玻璃纤维含量的增加呈非线性增加,当添加相同含量的玻璃纤维时,LGF/PA 6复合材料的冲击强度高于SGF/PA 6复合材料;两种界面相容剂均改善了玻璃纤维与PA 6的界面性能,显著提高了复合材料的冲击强度,其中添加PP-g-MAH的LGF/PA 6复合材料的冲击强度的提高高于添加POE-g-MAH的,但拉伸强度和弯曲强度均有不同程度降低,其中添加POE-g-MAH的LGF/PA 6复合材料的拉伸强度、弯曲强度和弯曲模量下降得较为明显。     

Mechanical properties of particulate composites

The mechanical properties of glass bead (30 micron diameter glass spheres) filled epoxy and polyester resins have been studied as a function of volume fraction of filler and the strength of the interfacial bond. The bonding between glass and resin was varied by chemically surface treating the glass using a silicone mold release to prevent chemical bonding at one extreme and a silane coupling agent to maximize bonding at the other extreme. Theoretical predictions of the elastic modulus and tensile strength have been made utilizing a finite element method. Excellent agreement is obtained with the experimental results. Izod impact energies have been measured for these composites as a function of filler content and interface treatment.     

Preparation and properties of PAN-based carbon fiber-reinforced SiCO aerogel composites

To overcome the brittleness issue of SiCO aerogels, the polyacrylonitrile-based (PAN) carbon fiber was impregnated with SiCO sol to obtain carbon fiber-reinforced SiCO aerogel composites (C/SiCO). SiCO sol was prepared through an acid-alkaline two-step catalysis by using methyltrimethoxysilane (MTMS) and dimethyldiethoxysilane (DMDES) as precursors. C/SiCO-1, C/SiCO-2 and C/SiCO-3 were obtained after repeated impregnation of the SiCO sol and gelating, aging, supercritical drying and pyrolyzing one to three times. SEM images show that the SiCO aerogel fills the pores between the carbon fibers, and the nanoporous structure of the SiCO aerogel can effectively improve the thermal insulation of the composites. As the times of impregnation of the SiCO sol increased, the mechanical properties and oxidation resistance of C/SiCO have been improved significantly. The bending strength of C/SiCO-3 was 32.52 MPa, and the compressive strength (25%ε) was 51.98 MPa. After heating at 1600 °C, the linear shrinkage in the thickness direction of C/SiCO-1 was 20.72%, while that of C/SiCO-3 was only 1.85%. A dense SiO₂ molten oxide film formed on the surface of C/SiCO at high temperature, and its extremely low oxygen permeability effectively protected the inside of the composites.     

Bamboo fiber-reinforced polypropylene composites: A study of the mechanical properties

A new type of bamboo fiber-reinforced polypropylene (PP) composite was prepared and its mechanical properties were tested. To enhance the adhesion between the bamboo fiber and the polypropylene matrix, maleic anhydride-grafted polypropylene (MAPP) was prepared and used as a compatibilizer for the composite. The maleic anhydride content of the MAPP was 0.5 wt %. It was found that with 24 wt % of such MAPP being used in the composite formulation, the mechanical properties of the composite such as the tensile modulus, the tensile strength, and the impact strength all increased significantly. The new composite has a tensile strength of 32–36 MPa and a tensile modulus of 5–6 GPa. Compared to the commercially available wood pulp board, the new material is lighter, water-resistant, cheaper, and more importantly has a tensile strength that is more than three times higher than that of the commercial product. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1891–1899, 1998     

Mechanical properties of silver-powder-filled polypropylene composites

Mechanical properties, such as tensile and flexural properties, as well as impact behavior of silver-powder-filled isotactic polypropylene composites were investigated in the composite composition range of 0–5.6 vol% of Ag. Tensile modulus, strength, and elongation at break decreased with incorporation of silver and an increase in silver concentration. Analysis of tensile strength data indicated the introduction of stress concentration and discontinuity in the structure upon addition of Ag particles. Izod impact strength decreased sharply on addition of 0.43 vol % of Ag particles, beyond which the value decreased marginally. Both flexural modulus and strength increased with filler content due to an increase in rigidity. Surface treatment of filler marginally improved mechanical properties. © 1996 John Wiley & Sons, Inc.     

Mechanical properties of mica-reinforced polypropylene composites

The influence of muscovite mica on the tensile, flexural, and mold shrinkage properties of composites with polypropylene (PP) were investigated. The best results in tensile and flexural properties at room temperature were observed for the physicochemical-treated mica followed by silane-treated mica. The mechanical properties could be correlated with the PP-mica interactions, as observed in the scanning electron microscope (SEM). In the present study, with mica aspect ratio equal to about 30, the optimum performance was obtained for the average flake diameter 80 ⩽ d (μm) ⩽ 280. Finally, the results of coloration and weathering are discussed. It was found that the PP/30 percent mica formulation has superior weathering characteristics over the neat PP resin.     

Carbon fiber-reinforced composites: Effect of fiber surface on polymer properties

Dynamic mechanical measurements in a torsional (shear) mode have been used to characterize an unfilled epoxy (Epon 828/m-phenylene diamine) and A series of uniaxial graphite fiber (Hercules types A and HM) composites. In unfilled resins containing an excess of the epoxy component, M_c—the average molecular weight between crosslinks—decreases with increasing temperature and duration of cure, suggesting a temperature-dependent side reaction. In fiber-reinforced composites, the dynamic mechanical response is sensitive to fiber type and curing schedule; elevation of T_g by as much as 45°C has been observed. Comparison of the dynamic data with properties predicted by micromechanical models shows only a fair agreement at room temperature, which rapidly worsens at higher temperatures. Surface treatment of type A fibers gives enhanced interlaminar shear strength (ILSS), both at ambient conditions and after hydrothermal aging. Dynamic data for surface-treated systems during hydrothermal aging show a sharper drop in G′ and increase in tan δ. The dynamic data and ILSS results are interpreted in terms of a balance of polymer-fiber interactions, a weak but widespread preferential adsorption of epoxy oligomers on the graphite basal planes at the fiber surface, and a low concentration of covalent bonds between polymer and fiber-surface-functional groups.     

Weathering of fiber-reinforced epoxy composites

Unless suitably stabilized and coated, fiber-reinforced composites are subject to photoinitiated oxidation which results in a degradation of the resin surface and an eventual reduction in the composite's mechanical properties. The photo-oxidation, which is initiated by UV-absorbing oxidation products created during cure, is relatively amenable to detection by techniques of analytical chemistry. Mechanical test results, which reflect a wide range of material properties, are more subject to variability and misinterpretation.     

Properties of UHMWPE fiber-reinforced composites

Based on our previous work, a new thermosetting resin system, named PCH, has been developed to be used as the matrix of ultrahigh-molecular-weight polyethylene (UHMWPE) fiber composites in order to get improved interface bond and mechanical properties. In this work, UHMWPE fiber/PCH composites with different ratios of PCH/styrene were prepared and the impact resistance, dynamic mechanical properties, and dielectric properties of UHMWPE fiber/PCH composites were investigated. The interlaminar shear failure characteristic of composites was analyzed by introducing a series of energy indexes indicating the energy absorbed in interlaminar shear failure process, which show good correlation with interlaminar shear strength of samples. UHMWPE fiber/PCH composites have excellent impact property, and the impact strength can reach 140.8 kJ/m² as the ratio of PCH/styrene is 60/40. Dynamic mechanical analysis showed that UHMWPE fiber/PCH composites have high storage moduli (E′) and low dissipation factor (tan δ) and these properties are influenced by the interfacial adhesion. The dielectric property test demonstrated that UHMWPE fiber/PCH composites have low dielectric constant (2.20 < ε′ < 2.55) and dielectric loss tangent (1.50 × 10^?3 < tan δ < 1.81 × 10^?2) and show good stability in a large range of frequency and temperature.     

The properties and suitability of commercial bio-based epoxies for use in fiber-reinforced composites

Environmental concerns about fiber composites are leading manufacturers to consider bio-based alternatives to petroleum-derived epoxies. Such a substitution is hindered by a lack of information, so commercially available bio-based epoxy systems have been compared, their mechanical properties measured, and fiber composites produced by vacuum infusion. Most high bio-based content resins for infusion use conventional curing agents. Bio-based content is generally added using Epicerol, but also other bio-based precursors. A diglycidyl ether of bisphenol A system produced using Epicerol achieves 20 % bio-based content, but achieves higher contents when Epicerol is used in diluents. Fully bio-based monomers can be deleterious to the mechanical properties and glass transition temperature (T_g), so are used sparingly. The most-promising systems (28 % to 43 % bio-based) compare well to conventional epoxies, possessing good strength, stiffness, toughness, and a reasonable T_g. These partially bio-based epoxies offer an immediate lower-carbon alternative for vacuum-infused composites in marine, sports equipment, and wind energy.