Processing of highly elastomeric toughened cyanate esters through a modified resin transfer molding technique

Abstract

Model cyanate ester resins containing different quantities of epoxy functional butadiene‐acrylonitrile rubber (ETBN) to improve the fracture performance were developed as matrices for composites. With the elastomeric modification, the resin systems exhibited rheological characteristics inappropriate for laminate fabrication by conventional resin transfer molding (RTM). To fabricate the carbon fiber based laminates in one liquid molding operation successfully, a process named bleed resin transfer molding (BRTM) was established. The BRTM process combines features of RTM and resin film infusion processes (RFI) and was therefore appropriate for processing high viscosity matrix resins. A novel catalyst was selected for the cyanate ester resin that provided enough latency for the impregnation steps in the BRTM process. Through the use of thermal analytical tools, a high degree of phase separation and conversion was obtained. The conversion and the glass transition temperature were found not to decrease with increasing elastomer content, which is in contradiction to most toughening modifications. Mode I and Mode II interlaminar fracture toughness were found to increase significantly with increasing elastomer content. In Mode I, an increase of up to 140% was observed. Collectively, this work showed that through the use of the BRTM technique, matrices with toughness improvements usually only achieved by prepreg systems can be processed in an RTM‐like manner.

Environmental effects on thermoplastic and elastomer toughened cyanate ester composite systems

“…As has been reported previously, highly crosslinked matrices with a tough second phase rarely lead to sufficient increases in mode I fracture toughness. [27][28][29] Optical microscopy of polished crosssections revealed that all four materials were well impregnated and essentially void free. It was found that a second phase (dark areas) was formed in the PS-modified cyanate ester (Fig.…”

Reinforced Cyanate Ester Resins with Carbon Nanotubes: Surface Modification, Reaction Activity and Mechanical Properties Analyses

“…So, appreciative modification is required to improve its toughness. Various methods such as copolymerization with flexible monocyanates monomer [6] , maleimide monomer [7] , utilization of reactive liquid rubber [8][9][10] , oligodimethylsiloxane [11] , thermoplastics [12] , and preparation of semi-interpenetration networks (S-IPNs) [13] have been proven useful for the toughness of CE resins. Besides, the incorporation of inorganic nanostructures with high strength, stiffness and enormous aspect ratio, such as carbon nanotubes [14] , clay [15] , rectorite [16] and montmorillonite [17,18] , also possess potential application for the toughness of the CE resins.…”

Evaluation of fiber surface treatment and toughening of thermoset matrix on the interfacial behaviour of carbon fiber-reinforced cyanate matrix composites

“…Thus, several attempts have been made to improve the toughness of cyanate ester by adding elastomers or thermoplastics [5][6][7][8][9][10][11][12]. Traditionally, the most successful method has been the addition of a suitable elastomer to the uncured resin [2,[5][6][7][8]. However, in the last years, the modification with high-performance thermoplastics has been more investigated because of the advantage, as compared to rubber modification, that there is no reduction in thermal and mechanical properties of the cyanate matrix [5][6][7][9][10][11][12].…”

“…High performance polymer matrix composites based on carbon fiber and cyanate ester resins have gained a great deal of attention in the aerospace industry because of their excellent thermal and dielectric properties also having similar processability to conventional epoxy based composites [1][2][3]. Nevertheless, although cyanate ester resins are known to be relatively tough compared with other thermosetting matrices, some applications require improved fracture resistance [4].…”