Influence stacking sequence and heat-treatments on the out-of-plane mechanical properties of 3D printed fiberglass-reinforced thermoplastics

Abstract

Abstract Additive manufacturing of composite materials is a promising technology. It could solve one of the most critical drawbacks of 3D-printed fiber-reinforced thermoplastics: their low out-of-plane mechanical properties. However, due to their novelty, the number of standards and research papers addressing the characterization of these materials is scarce, especially in the out-of-plane direction. Due to this factor, it is still unknown how most design and manufacturing parameters affect the out-of-plane properties of composite materials. As a solution, this paper proposes an experimental methodology to characterize out-of-plane printed composite materials. For this purpose, existing standards for traditionally fabricated composites are adapted, investigated, and validated for 3D-printed laminates reinforced with long fibers using the fused filament fabrication technique. Consequently, the methodology is employed to study the impact of stacking sequence and heat treatment conditions on the composites' out-of-plane mechanical properties. The main results showed that increasing the thickness between stacking layers increases the mechanical response due to reducing the number of fiber/matrix interfaces and, consequently, the reduction of porosity. Compared to the initial sample, a heat treatment at 175°C for 6 hours increased the interfacial strength by 101.09% and reduced the porosity in the fiber produced by the additive manufacturing process by 72%.