Investigation of facile strategy for eliminating internal cracks of pultruded carbon fiber composites

Internal crack usually occurs in carbon fiber reinforced polymer composites (CFRP) with large section or big thickness produced by pultrusion, which will affect the performance of products. In this paper, for eliminating the cracks and increasing the physical properties, different reinforced fibers and winding layers were adopted for enhancing circumferential binding force. Besides, superfine fillers were appropriately added and curing temperature was adjusted for optimizing resin curing reaction. The tests had proved that, when the composite rod covered with a 45° winding layer, filled with glass fiber as inner layer along with superfine filler, it could help restrain the propagation of cracks. In addition, thermal stress caused by inhomogeneous curing reaction was the most critical factor leading to cracks. Moreover, this work also engaged in introducing preheating and exothermic zone and moving the gelation and solidification zone forward, which had helped reduce temperature gradient and facilitated the simultaneous curing of resin. This study provides a facile strategy to rationally avoid thermal concentration in the inner core and decreased thermal stress, thereby eliminating the cracks and promoting the performance of CFRP rods produced by pultrusion.