Effect of pressure-free heating curing time on bending property of 2D T700/E44 composites prepared by ICM

Abstract

Six kinds of 2D T700/E44 composites with pressure-free curing times of 40 min, 60 min, 80 min, 100 min, 120 min and 140 min are prepared by improved compression molding process (ICM). The macroscopic morphology of the composites is satisfactory. The microstructure observation and bending performance tests show that composites have poor infiltration effect. When the pressure-free curing time is less than 80 min, defects are easy to occur such as insufficient infiltration and voids. Bad infiltration and void defects will lead to poor continuity of carbon fiber and resin, and their bending fracture will also be unreasonable, so the bending strength of composite at 40 min is 275 MPa. The infiltration effect is gradually improved with the increase of pressure-free heating curing time. However, when the pressure-free heating curing time reaches 120 min or more, the infiltration effect of the composites is deteriorated, and this is due to excessive infiltration time and extrusion force in subsequent heating extrusion infiltration process. Defects such as fiber aggregation and uneven infiltration are prone to occur, and bending strength of composites reduces to 380 MPa. When the pressure-free curing time is 100 min, the infiltration effect of the prepared composite is satisfactory, and the imbalanced infiltration and hole defects are effectively eliminated. The bending fracture of composite material is uneven, carbon fibers and resin play the roles of reinforcement and transferring loads effectively respectively, so the bending strength of the prepared 2D T700/E44 composite reaches 730 MPa.