Polyester composites tensile properties

In the late 1980s, new fully aromatic polyester fibers were iatroduced for use ia composites and stmctural materials (18,19). In general, these materials are thermotropic Hquid crystal polymers that are melt-processible to give fibers with tensile properties and temperature resistance considerably higher than conventional polyester textile fibers. Vectran (Hoechst-Celanese and Kuraray) is a thermotropic Hquid crystal aromatic copolyester fiber composed of -hydroxyben2oic acid [99-96-7] and 6-hydroxy-2-naphthoic acid. Other fully aromatic polyester fiber composites have been iatroduced under various tradenames (19). 

This moldable material primarily consists of TS polyester resin, glass fiber reinforcement, and filler. Additional ingredients, such as low-profile additives, cure initiators, thickeners, and mold-release agents are used to enhance the performance or processing of the material. As with any material, such as metallics and plastics, SMC can be formulated in-house or by compounders to meet performance requirements of a particular application such as tensile properties or Class A surface finish. Varying the type and percentage of the composition will result in variations in mechanical properties and processability. 

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. 

S.B. Srahim, R.B. Cheikh, Influence of fibre orientation and volume fraction on the tensile properties of unidirectional Alfa-polyester composite. Compos. Sci. Technol. 67(1), 140-147 (2007)... 

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. 

Le Digabel F, Boquillon N, Dole P et al (2004) Properties of thermoplastic composites based on wheat-straw lignocellulosic fillers. J Appl Polym Sci 93 428-436 Lee S -R, Park FI-M, Lim H et al (2002) Microstructuie, tensile properties, and biodegradability of aliphatic polyester/clay nanocomposites. Polymer 43 2495-2500 Lee SFI, Ohkita T, Kitagawa K (20(M) Eco-composite from poly(lactic acid) and bamboo fiber. Flolzforschung 58 529-536... 

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]. 

Mishra et al. [36, 37] tested the tensile and impact strength of maleic anhydride-treated sisal composite at different fiber volumes and found that tensile and impact strength decreased gradually from 40% fiber volume composite to 55% fiber volume polyester composite. It was concluded that maleic anhydride-treated composite at fiber volume 40% showed higher and better mechanical properties [36, 37]. Related to tensile properties evaluation, Mishra et al. [36, 37] concluded that a composite of alkali treated (5%) sisal fiber was fotmd to achieve better mechanical properties as compared to rmtreated, dewaxed, 10% alkali treated and bleached sisal fiber-reinforced composites. A 5% alkali-treated sisal fiber-reinforced composite... 

G.V. Reddy, S.V. Naidu and T.S. Rani, Kapok/glass polyester hybrid composites tensile and hardness properties. /. Reinf. Plast. Compos. 27,1775-1787 (2008). 

Effect of fiber loading The loss in tensile properties of OPF-polyester composites upon degradation in soil was quantified by. Loss in tensile strength by 8%, 17% and 35% were observed, respectively after exposure of 3,6 and 12 months. Similarly tensile modulus, elongation at break and impact strength also reduced upon soil exposure. A loss of impact strength by 6%, 18% and 43% were observed, respectively after 3, 6 and 12 months. Similarly the tensile stress, tensile modulus and elongation at break decreased from 35.1 MPa, 3.29 GPa and 3.75%, 34.6 MPa, 2.32 MPa and 2.48%, respectively upon soil burial for 12 months [61]. 

---