Liquid crystalline single-polymer short-fibers composites

Abstract

Single-polymer short-fibers composites (SPSFCs) were obtained by including Vectran ® fibers in a Vectran ® matrix. A thermal annealing treatment was optimized to increase the melting temperature, mechanical properties, and thermal stability of pristine Vectran ® fibers, and a two-step process was successfully developed to consolidate SPSFCs containing up to 30 wt.% of reinforcement. The composites exhibited a remarkable improvement of the tensile modulus (up to 161%) and a decrease of elongation at break in comparison with the unfilled matrix. A slight decrease of the composites tensile strength was also observed which suggested an investigation of the matrix-reinforcement interfacial adhesion. SEM observations evidenced some pull-out phenomena, indicating a poor interfacial adhesion. A plasma surface treatment on the reinforcing fibers was performed in order to increase the interfacial adhesion in the composites. The results showed an increase of almost 180% in the tensile modulus compared with the unfilled matrix and fiber breakage as main fracture mechanism.

Hybridization of short glass fiber polypropylene composites with nanosilica and graphite nanoplatelets

“…Therefore, a more appropriate empirical model proposed by Tsai and Pagano 34 was applied to predict the elastic modulus ( E GF ,TP ) of composites containing short fibers randomly oriented in a plane (equations (9) to (11)). Furthermore, since the short fibers are supposed to be randomly oriented throughout all the composite volume, the Christensen and Waals model 35,36 was used to estimate the elastic modulus ( E GF ,CW ) in three-dimensional randomly distributed short fiber composites (equation (12)) where the subscripts L and T stand for longitudinal and transversal, while ξ L and ξ T is assumed as 2 a and 2, respectively, according to the Tsai and Pagano’s theory where E f is the elastic modulus of the glass fibers, ϕ f is the fiber volume content, while ν m is Poisson’s ratio of the matrix. In the case of SGF composites the aspect ratio ( a ) was experimentally measured on each sample.…”

Liquid crystalline polymer nanocomposites reinforced with in-situ reduced graphene oxide

“…Commercially available Vectran ® NT fibers having a linear density of 750 denier and 150 filaments/yarn and a circular cross-section with an average diameter of 25.5±2.1 µm [38] were provided by Kuraray America Inc. (Fort Mill, USA). This special type of LCP is a thermotropic copolyester obtained by polycondensation of p-Hydroxybenzoic acid (HBA) and 6-hydroxy-2-naphthoic acid (HNA) in the molar ratio 73:27 ( Figure 1).…”

“…At this aim, a liquid crystalline polymer (LCP) matrix, known as Vectran ® , was chosen for the present research, because of its extremely high thermal stability and excellent mechanical properties [35]. In particular, thermotropic main chain LCP copolyesters represent a class of high-tech polymers which combine high mechanical performances with low density, resulting in outstanding specific properties [35][36][37][38]. Their typical applications include electronic devices, fiber optic coupling discs, automotive components, and sport equipment.…”

Flexural and low velocity impact characterization of thermoplastic composites based on PEN and high performance woven fabrics

“…Vectran fibers were introduced as commercial products in the mid‐1980's but their application in fiber reinforced composites is limited. Most of the studies deal with the use of Vectran in single polymer composites , but recently they have been investigated as stitch fibers in carbon fiber reinforced composites showing better reinforcing capability when compared to Kevlar and carbon fibers .…”