Polyester composites flexural properties

Carbon nanofiber, imsaturated polyester, polymer-nanoparticle-long fiber composites, flexural properties, vacuum assisted resin transfer molding... 

The flexural and tensile properties of polyester composites at various fiber volume fractions are listed in Table I. Strength values increase up to a fiber volume fraction of about 40% but then decrease with increased fiber volume fraction. This is caused by the poor wetting and extensive fiber damage which occurs at higher volume fractions because of compaction and close packing of the fibers. The ultimate flexural strain shows a similar trend. The modulus values increase almost linearly with fiber volume fraction. 

Mouritz AP. Post-fire flexural properties of fibre-reinforced polyester, epoxy and phenolic composites. J Mater Sci 2002 37 1377-86. http //dx.doi.Org/10.1023/A 1014520628915. 

Sathishkumar, T.P., Navaneethakrishnan, P., and Shankar, S. (2012) Tensile and flexural properties of snake grass natural fiber reinforced isophthallic polyester composites. Compos. Sci. Technol, 72 (10), 1183-1190. 

Boynard CA, Monteiro SN, d Almeida JRM (2003) Aspects of alkali treatment of sponge Gourd (Luffa cylindrica) fibers on the flexural properties of polyester matrix composites. J Appl Polym Sci 87 1927-1932... 

Thermoset composites are made up of thermoset resin-like polyester epoxy and phenol-formaldehyde resin composites with varying fiber volume fractions and fiber length were prepared by following one of the techniques. Among polyester epoxy and phenol-formaldehyde composites, a phenolic-type resin performed as a better matrix than epoxy and polyester resins with respect to tensile and flexural properties due to the high interfacial bonding in phenolic composites [58,59,100]. 

Variation in tensile, impact, and flexural properties of thermoset composites, viz. sisal-polyester, sisal-epoxy, and sisal-phenol-formaldehyde is explained here, with the change in length of the fiber (5-30 mm), fiber volume, etc. 

The tensile and flexural behavior of sisal fiber-reinforced polyester composites were investigated as a function of fiber length and fiber content by Sreekumar et al. [101]. Resin transfer molding and compression molding techniques were used for composite making. From the studies, it was found that mechanical properties increased with an increase in fiber loading in both cases [101]. 

Neat polyester composite showed tensile strength around 41 MPa, Young s modulus around 9.68 GPa, and flexural strength around 61 MPa. After reinforcement with fiber, mechanical properties were enhanced and some of the important properties are explained below. Singh et al. [102] reported that sisal-polyester composites from nonwoven sisal mats with fiber content 50% by volume showed a tensile strength of 30 MPa and a tensile modulus of 1.15 GPa. The composites were manufactured by impregnation of the nonwoven sisal mats under compression molding for 2 hrs [9, 102]. 

Investigations have shown that it is possible to manufacture all-natural composites using hemp and flax fibres using soy oil resins [14]. The tensile and flexural properties of the resins were shown to be improved by the addition of the fibres as observed for regular thermoset resins. However, this type of composite gave lower values than polymer-natural fibre-reinforced composites. Wollerdorfer and Bader [15] made similar observations for different all-natural composites using soya resins. Researchers [16] have reported studies on the properties of composites from hemp non-woven mats and polyester resin. The authors observed that mechanical properties were found to reach maximum at a fibre loading of 30%. 

Chen and Lein [26] have described a proprietary process for the manufacture of pultruded hybrid fiber (glass/carbon)-reinforced unsaturated polyester composites. To investigate the effect of reinforcement type and content on the properties, composites with various fiber contents were fabricated. Flexural strength, flexural... 

Flexural properties of various jute/polyester composites are given in Table 2. 

Glass fiber reinforced composites based on epoxy-acrylate modified UPRs were studied [228]. The authors showed that UPRs, endcapped with acrylate groups and diluted with reactive multifunctional acrylic and allylic monomers in the presence of a photoinitiator, can be photocrosslinked with UV radiation as glass fiber laminates in a rapid process. It was found that the physical properties of the photo-crosslinked laminates are well correlated with the molecular weight of the polyester, the amount of multifunctional monomer added, and the glass fiber content. A greater improvement of the tensile and flexural properties of the photocured products was observed for multifunctional acrylate or acrylether monomers added to the UPR (Table 31) than for allylic monomers. 

Tensile, flexural and interlaminar shear properties of woven jute and jute-glass fabric reinforced polyester composites. J. Mater. Process. Technol, 207, 330-335. 

Sreekumar et al. (2008) have reported the effect of fiber content in polyester composites and have reported 40% volume fraction to show maximum tensile strength. Sapuan et al. (2006) investigated the mechanical properties of woven banana fiber reinforced with epoxy composites. Tensile strength. Flexure, impact and fracture surface study of woven pseudo stem banana fiber reinforced with epoxy composites was reported and the chemical modification of kenaf fiber was carried out by Edeerozey et al. (2007). Anuar et al. (2011) studied the thermal... 

Mechanical Properties. The performance of various polyester resin compositions can be distinguished by comparing the mechanical properties of thin castings (3 mm) of the neat resin defined in ASTM testing procedures (15). This technique is used widely to characterize subtle changes in flexural, tensile, and compressive properties that are generally overshadowed in highly filled or reinforced laminates. 

Table in also shows the effect of BG content on the properties of injection-molded BDft/BG/BD polyesters. The two copolyesters which contained 65 and 73 mol % BG and did not solidify during preparation were molded in their anisotropic state (Ti s above molding temperatures), and it is significant that these two ICP s have the highest tensile, flexural, and impact properties (and the highest HOT s at 264 psi stress). The other four compositions in the table became solid or semi solid during preparation at 300°C, and additional molecular weic t buildup was achieved by solid-state polymerization to give I.V. s comparable to... 

---