Joining of C/C–SiC using boron-modified phenolic resin with SiO₂and B₄C additives

Abstract

Joining of carbon fibre reinforced C -SiC dual matrix composite has been realized through a reaction joining process using boron-modified phenolic resin with B 4 C and SiO 2 additives. The effect of the technological parameters on the strength of joints was investigated. The optimized technological parameters are the curing temperature of 200 C, the curing time of 2 hours and the curing pressure of 30 kPa, under which conditions, the obtained strength of the joint is equal to 82.6% of that of the substrate. The interlayer composed of Si, C, B and O is basically uniform and dense. There are no obvious cracks nor pores at the interfaces. The elements migrate across the interfaces, contributing to the enhancement of the joint strength. The results of heat treatment at 1500 C show good heat resistance of the joints. The B 4 C and SiO 2 additives contribute to the densification of the interlayer and the adhesion at the interfaces.

Low‐temperature curable adhesive for joining SiC/SiC components: Their application in wide range of temperatures

“…The SiC substrates of size 20 × 10 × 5 mm 3 (LXWXH) were pre‐cleaned by ultra‐sonication in isopropyl alcohol and dried in an oven for 2 h. The phenolic adhesive made as per the above method was applied to these SiC substrates in the 1 × 1 cm 2 area; subsequently, the substrates were fixed as lap joints using C‐clamp and tightened using hand (no other external pressure was used). After joining with phenolic adhesive, these lap SiC–SiC joints were then cured at 200°C for 2 h 15. During the curing process, the rate of heating from ambient temperature to 200°C was maintained at 10°C/min and after completion, the temperature of the oven was naturally brought down to ambient temperature.…”

“…The filler constituents used in this adhesive were found to form a mixture of high‐temperature glass and non‐liquefied solid. Consequently, this eutectic mixture was found to be responsible for filling the pores and cracks in bonding area and imparting the heat resistance to the joints up to 1500°C 15 . However, the joining methodology and the joint stability in this case were limited to vacuum conditions.…”

“…It is well known that the volatile content in phenolic resin has direct influence on the formation of cracks, increment in porosity, and the generation of massive residual stresses. 15 As a result, the direct utilization of phenolic resin as an adhesive for joining SiC substrates is expected to show lower shear strength values and hence need modification by adding suitable filler materials. On the other hand, the TGA profile of phenolic adhesive shows weight loss and weight gain both between 50 and 1500 • C. It shows nearly 21.5% (ceramic yield of 78.5%) of weight loss from 50 to 620 • C and nearly 20.8% weight gain from 620 to 1500 • C. The weight loss that occurred between 50 and 620 • C was found to be almost compensated by weight gain that occurred between temperatures from 620 to 1500 • C. These changes could be ascribed to the degradation of phenolic resin followed by the chemical transformations involved in the active filler, respectively.…”

“…The filler constituents used in this adhesive were found to form a mixture of high-temperature glass and non-liquefied solid. Consequently, this eutectic mixture was found to be responsible for filling the pores and cracks in bonding area and imparting the heat resistance to the joints up to 1500 • C. 15 However, the joining methodology and the joint stability in this case were limited to vacuum conditions. The real-time aerospace applications require heat-resistant SiC joints sustainable under oxidative environment and also require the joining procedures that are feasible at relatively low temperatures and normal pressure conditions.…”

“…13 Hence, the adhesive that can result in high ceramic yields at high temperatures and binding the SiC segments with good shear strength values at low temperatures is necessary. 14 In this scenario, Chen et al 15 reported an adhesive made by combining boronmodified phenolic resin (PCMC) and a high-temperature glass-forming SiO 2 , B 4 C as filler to join C f -SiC substrates utilizing a reaction-bonded joining process under vacuum and axial pressure conditions. The joint made with this adhesive showed the strength of 12.6 MPa at room temperature.…”