Experimental Evaluation of Interface Adhesion of a Flax Fiber Composite Patch with Epoxy and Polyurethane Adhesives for the Reinforcement of Steel Structures

Abstract

Using fiber-reinforced composite patches for repairing damaged structures made of metal or/and concrete is an interesting and widely available solution on the market using synthetic materials. These repairing patches are bonded on the structures’ surfaces to increase their strength against internal stresses, as well as protect them from external physico-chemical attacks, thereby limiting crack propagation. Natural fibers offer a potential alternative to replacing glass or carbon fibers commonly used for bonded repair patches. Similarly, bio-based polymers represent an important sustainable alternative for partially or entirely replacing the petroleum-based polymers. In this study, an epoxy matrix reinforced with flax fiber is proposed as the material for the patches, and bonded to a steel plate using four different types of adhesive materials, including a castor-oil derived polyurethane resin. Floating roller peel tests were performed to assess the adhesion and viability of these new patches. The resulting peeling loads and fracture surface analysis are presented. Polyurethane demonstrates promising performance for epoxy-to-steel joints, but major improvements of the bio-based polyurethane application process and curing conditions may be necessary for its successful industrial implementation.

Mohamed Amine TAZI

PhD Candidate (co-supervised with CESI-France)

Curious and passionate about science—especially solid mechanics—I am interested in the application of composite materials across various industrial sectors, with a focus on enhancing their mechanical performance and environmental sustainability.

Rosemere de Araujo Alves Lima

Postdoc Researcher

I am an MSCA postdoctoral researcher working on toughening and self-sensing strategies for smart, reversible adhesive joints. My research combines 3D printing, structural health monitoring, and multifunctional materials to enable the development of next-generation circular adhesively bonded composite structures.

Sofia Teixeira de Freitas

Principal Investigator

Sofia Teixeira de Freitas researches the structural integrity of bonded and layered materials to enable durable, sustainable structures. She is also an accredited group facilitator, committed to building academic environments grounded in cooperation and inclusion—key to overcoming technological limits and addressing the challenges of a truly sustainable society.