Test Methods for Fibre/Matrix Adhesion in Cellulose Fibre-Reinforced Thermoplastic Composite Materials: A Critical Review

Abstract

Due to the increasing discussion about sustainable and CO2-reduced materials, the demand for cellulose-based fibres as a reinforcing component in thermoplastic composites has increased considerably. Knowledge about the possibilities of modifying fibres for improved adhesion to the plastic matrix is essential in this context. The fibre/matrix adhesion in cellulose fibre-reinforced polymers is of considerable importance for the design of composite materials. Unfortunately, there are no standards for many essential methods to determine fibre/matrix adhesion. In this review article, various methods for measuring the interfacial shear strength between fibres and matrix, as an indirect characterisation of adhesion, are presented. Additionally, a brief overview of different methods for surface modification of cellulose fibres to improve the adhesion to a thermoplastic matrix is given. This review focuses on the fact that the parameters for the production of test specimens as well as the test method itself can vary considerably from study to study. Because of this, the comparison of data from different publications is not always possible. Therefore, in this article, the main influencing factors and differences in the methods are presented and discussed. Based on a systematic review and a clear description and discussion of the methods, the reader is given a broad basis for a better understanding of characteristic values for fibre/matrix adhesion.

Extraction and Characterization of Fiber Treatment Inula viscosa Fibers as Potential Polymer Composite Reinforcement

“…[1][2][3][4]. Researchers and scientists are currently focusing on green composite materials from plants bers with good ber yields, cost-effective without compromising mechanical properties [5][6][7]. This is justi ed because, on the one hand, natural bers have the status of renewable and durable materials; on the other hand, they are abundant, light, of moderate resistance, high speci c modulus compared to synthetic ones [8][9][10].…”

Micromechanical Tests on Natural Fibre Composites with Enzymatically Enhanced Fibre–Matrix Adhesion

“…When applying micromechanical tests in order to study interfacial adhesion, a direct comparison of characteristic values is only possible within a test series in which exactly the same methods are used for preparation, testing and evaluation (Müssig and Graupner 2020). Tests on natural fibre composites add some specific issues due to the characteristics of natural fibres.…”

“…The concept of single fibres is different than in synthetic fibres. A single fibre is basically one dried plant cell (Müssig and Graupner 2020). It is limited in length, often to 1 cm or less, with pointed tips.…”

“…The SFPO as has been used here provides quantitative data of the interfacial shear parameters. The apparent shear strength is the parameter most often determined (Müssig and Graupner, 2020). It is based on the simplification that there is a constant shear stress at the fibre-matrix interface, and will therefore depend on the embedding length.…”

“…Micromechanical tests on single fibre model composites are especially sensitive to shear stress (Kim and Mai 1998;Herrera-Franco and Drzal, 1992). In the field of natural fibre composites, some micromechanical tests have been reported (Li et al 2009;Doan et al 2012;Graupner et al 2014;Thomason and Rudeiros-Fernández 2021;Müssig and Graupner 2020). The present study compares two micromechanical tests and their use in natural fibre composites, namely the single fibre pullout test (SFPO) and single fibre fragmentation test (SFFT).…”