Effect of tow size and interface interaction on interfacial shear strength determined by Iosipescu (V-Notch) testing in epoxy resin

Testing methodologies to accurately quantify interfacial shear strength (IFSS) are essential in order to understand fiber-matrix adhesion. While testing methods at a microscale (single filament fragmentation test-SFFT) and macroscale (Short Beam Shear-SBS) are wide spread, each have their own shortcomings. The Iosipescu (V-notch) tow test offers a mesoscale bridge between the microscale and macroscale whilst providing simple, accurate results with minimal time investment. However, the lack of investigations exploring testing variables has limited the application of Iosipescu testing to only a handful of studies. This paper assesses the effect of carbon fiber tow size within the Iosipescu tow test for epoxy resin. Tow sizes of 3, 6, and 9 k are eminently suitable, while more caution must be shown when examining 12, and 15 k tows. In this work, tows at 18 and 24 k demonstrated failure modes not derived from interfacial failure, but poor fiber wetting. A catalogue of common fracture geometries is discussed as a function of performance for the benefit of future researchers. Finally, a comparison of commercial (T300), amine (T300-Amine), and ethyl ester (T300-Ester) surface modified carbon fibers was conducted. The outcomes of this study showed that the Iosipescu tow test is inherently less sensitive in distinguishing between similar IFSS but provides a more \u27real world\u27 image of the carbon fiber-epoxy interface in a composite material

A comparison of mechanical properties of recycled high-density polyethylene/waste carbon fiber via injection molding and 3D printing

Recycled high-density polyethylene (r-HDPE) was combined with waste carbon fiber by loading 6 k, 12 k, and 24 k tows through an extruder to create thermoplastic/carbon pellets with fiber volume fractions of 11.2%, 18.9%, and 29.5%, respectively. Tensile and flexural coupons were subsequently produced via injection molding and novel 3D printing. The addition of carbon into r-HDPE in all cases showed increased mechanical properties. Maximum increases were observed through the inclusion of 29.5% fiber volume fraction. Increases in tensile and flexural modulus of up to 2.9 GPa (+505.9%) and 5.8 GPa (+711.0%) respectively were observed for r-HDPE/carbon fiber (CF) samples. Increases in tensile and flexural strengths of up to 57.9 MPa (+311.8%) and 47.7 MPa (+188.0%) respectively were observed for 29.5% r-HDPE/CF samples. Some variance in mechanical performance between injection molded and 3D printed samples was observed indicating production methodology might influence final material performance

Using in situ polymerization to increase puncture resistance and induce reversible formability in silk membranes

Silk fibroin is an excellent biopolymer for application in a variety of areas, such as textiles, medicine, composites and as a novel material for additive manufacturing. In this work, silk membranes were surface modified by in situ polymerization of aqueous acrylic acid, initiated by the reduction of various aryldiazonium salts with vitamin C. Treatment times of 20 min gave membranes which possessed increased tensile strength, tensile modulus, and showed significant increased resistance to needle puncture (+131%), relative to \u27untreated\u27 standards. Most interestingly, the treated silk membranes were able to be reversibly formed into various shapes via the hydration and plasticizing of the surface bound poly(acrylic acid), by simply steaming the modified membranes. These membranes and their unique properties have potential applications in advanced textiles, and as medical materials