Quasi-Static Shear Test of Hybrid Adhesive Bonds Based on Treated Cotton-Epoxy Resin Layer

Abstract

This research evaluates the mechanical properties of hybrid adhesive bonds with various 100% cotton fabrics in static and quasi-static conditions and the influence of alkali surface treatment (NaOH) of the cotton fabrics on the mechanical properties. Biological fibers in polymers are characterized by low wettability with the matrix, which decreases mechanical properties. Adhesive bonds usually operate in cyclic stress, which causes irreversible failure before maximal strength. In this paper, a quasi-static test was used to load the adhesive bonds in 5–50% (192–1951 N) and 5–70% (192–2732 N) intervals with 1000 cycles. The results of SEM analysis showed good wettability of alkali treated cotton fabric with NaOH solution in hybrid adhesive bonds. The static test proved the influence of reinforcing cotton fabrics on shear tensile strength against pure resin, i.e., sample Erik up to 19% on 14.90 ± 1.15 MPa and sample Tera up to 21% on 15.28 ± 1.05 MPa. The adhesive bonds with pure resin did not resist either quasi-static tests. Reinforcing cotton fabrics resisted both quasi-static tests, even shear tensile strength increases up to 10% on 16.34 ± 1.24 MPa for the fabric Erik. The results of strain difference of adhesive bonds with Tera and Erik confirmed that a lower value of the difference during cyclic loading positively influenced the ultimate shear tensile strength.

Experimental Investigation of Wavy-Lap Bonds with Natural Cotton Fabric Reinforcement under Cyclic Loading

“…Polymers 2021, 13,2872 3 of 17 and procedure were chosen. That included selection of 100% cotton fabric as reinforcement [19]. The previous studies have focused on flat geometries, while some of the real applications are in the form of curved (wavy) shapes.…”

“…The mechanical properties of adhesive bonds could be influenced by physical and chemical factors (wettability, adhesion and cohesion, aging, and environmental degradation) [4,9,10], technological factors (roughness and structure of bonded surface and filler material) [11][12][13], and constructional factors (overlapping length and geometry and type of applied load) [14][15][16][17][18]. The resulting performance of the adhesive bond is governed by the synergy of these factors, i.e., the effect of their mutual interaction [19].…”

“…The surface treatment leads to improvement of interaction at the interphase boundary, i.e., on the interface of the natural reinforcement and matrix [37]. It leads to improvement of mechanical properties, especially the shear strength of adhesive bonds [19,35,38].…”

“…The tests of cyclic loading are essential for practical application of adhesive bonds [42][43][44]. The researchers demonstrated that the hybrid composite layer of adhesive bonding can positively influence the mechanical properties and extend their service life under cyclic loading [19,35,45].…”

“…Based on previous research to achieve optimum results for mechanical properties and service life during cyclic loading, the bonding materials and procedure were chosen. That included selection of 100% cotton fabric as reinforcement [19]. The previous studies have focused on flat geometries, while some of the real applications are in the form of curved (wavy) shapes.…”