Co-authors​ :

 Peter SÁNTHA (HUNGARY), Peter TAMÁS-BÉNYEI (HUNGARY) 

Carbon fiber-reinforced polymer (CFRP) composites have emerged as innovative materials for high-performance applications in multiple industries. The utilization of carbon fiber-reinforced composites has increased substantially in recent years, and projections indicate that the demand for these materials will continue to rise in the future. The widespread appeal of CFRP composites can be attributed to their reduced density, exceptional specific mechanical properties compared with metals, conductivity, and versatility in the design of composite products. CFRP materials play an important role in implementing increasingly stringent international greenhouse gas emission regulations and mitigation efforts. The increased volume of CFRP products and the growing demand for carbon fiber necessitate the industry to manage waste generated throughout the production and end-of-life cycle of composite structures.
As carbon fibre production is a high-energy and cost-intensive process, composite materials have high embedded technical value. Currently available recycling technologies allow for some level of recovery of reinforcing materials from composite waste, thereby enabling the circulation of material flow in the composite industry [1]. The reuse of recycled carbon fibers (rCF) can reduce raw material costs, opening the possibility of new applications for reinforcing fibers. On the one hand, the carbon fibers recovered by mechanical, thermal, chemical, and other special treatments possess comparable retained mechanical properties to virgin fibers. However, rCFs are typically in a discontinuous and random form because of the cutting process during manufacturing and size reduction during the recycling processes. Nonwoven reinforcements can effectively exploit the mechanical properties of discontinuous and randomly distributed rCFs. In stacking design, the incorporation of rCF nonwoven plies can significantly vary the toughness, damping capacity, and failure mode of hybrid composites [2]. The former parameters are crucial for the long-term behavior of composite structures, thus affecting the lifetime of the products.
This study aimes to investigate the potential of using recycled carbon fibers (rCFs) as interlayers to enhance the interlaminar fracture toughness of carbon fibre/epoxy composites. Herein, nonwoven mats based on rCFs and commingled rCF/PP fibers were used for the interlayer toughening of a unidirectional carbon/epoxy laminate, with the aim of improving mode-I and mode-II fracture toughness and fatigue performance. The fracture tests were equipped with acoustic emission (AE) and the morphology of the fracture surfaces was examined using optical and scanning electron microscopy.