Mechanical and thermal properties of CFRP recycled via a sustainable mild solvolysis process

Details

Supervisors

Pardoen, Thomas ; Nysten, Bernard

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil en chimie et science des matériaux, à finalité spécialisée

Abstract

enCarbon fiber reinforced plastics (CFRP) are widely used in aerospace and other high-performance applications due to their excellent mechanical properties and lightweight characteristics. However, the increasing use of CFRP has raised serious concerns regarding end-of-life management, as conventional recycling methods often require high temperatures and pressures, resulting in significant energy consumption and degradation of fiber quality. In this study, a mild recycling process based on formic acid solvolysis was investigated to enable the recovery and reuse of CFRP while preserving fiber architecture and functional interfacial characteristics. Virgin, first-recycled, and second-recycled CFRP laminates were fabricated using aerospace-grade RTM6 epoxy resin, and systematically characterized in terms of chemical structure, thermal behavior, and mechanical properties. FTIR and ICP-OES analyses revealed partial cleavage of the epoxy network, formation of hydroxyl and carbonyl groups, and progressive removal of fiber sizing during recycling. TGA and DSC results showed a decrease in resin content and the appearance of new thermal transitions in recycled materials, while DMA indicated additional relaxation behavior associated with chemically modified residual resin. Mechanical testing demonstrated contrasting trends depending on the loading mode: tensile properties showed partial recovery after the second recycling, whereas bending and interlaminar shear strength (ILSS) progressively decreased, highlighting the dominant role of matrix and interface degradation. These results demonstrate that the proposed formic-acid-based recycling approach does not fully remove the polymer matrix but instead enables controlled chemical modification of residual resin layers, which significantly influences interfacial and mechanical behavior. This work provides fundamental insights into interface-driven design strategies for recycled CFRP and contributes to the development of sustainable composite materials for high-performance applications.