Mechanics and Mechanical Engineering Vol. 22, No. 4 (2018) 885–893 c  Technical University of Lodz Improvement of the Interfacial Adhesion Between Fiber and Matrix Benaoum Abdelhak Laboratoire G´ enie Industriel et D´ eveloppement Durable, e-mail: hako.79@gmail.com Mahmoudi Noureddine Centre Universitaire Relizane, Relizane, Alg´ erie Mahmoudi Hacen Universite Hassiba ben bouali Chlef, Algerie Received (6 March 2018) Revised (12 September 2018) Accepted (14 September 2018) In this work, the influence of carbon fiber surface treatment on mechanical properties of unsaturated polyester was investigated. Two approaches have been used in the surface treatment; the first is the desizing of the carbon fiber by the release of the epoxy layer. The second is with the release of epoxy layer and etching the fibers. It was concluded that both methods give good results on adhesion between the matrix and the fibers. It is found that the treatment of carbon fibers is efficient and greatly improves the CFRP handress. The tensile strength of composite materials increases by 30% for etched carbon fibers compared to untreated carbon fibers.SEM images confirm the results obtained. Keywords : carbon fibers, surface treatment, desizing, mechanical properties. 1. Introduction Carbon fiber-reinforced polymer composites have many structural applications, in- cluding aircraft, sporting equipment, automotive, and civil structures due to their outstanding mechanical properties, light weight and high thermal stabilities [1]. The interfacial and mechanical properties of a fiber-reinforced polymer compos- ite are significantly influenced by interfacial characteristics between the reinforcing fibers and the polymer matrix. Especially for carbon fibers, the surface is an im- portant region that plays a contributing role in the interfacial behavior with the polymer matrix. Their interfacial characteristics can be chemically or physically al- tered by both fiber surface-treatment and desizing. Appropriate surface-treatment may modify the fiber surface by increasing the surface area and/or by increasing oxygen containing functional groups on the surface that may provide some chemical interactions between the fibers and the matrix resin [2]. https://doi.org/10.2478/mme-2018-0069