Experimental analysis of Tufting Parameter for Enhancing 3D Composites

This study investigated the experimental analysis of tufting parameters for enhancing three-dimensional (3D) composites, particularly focusing on the formation of lap joints in 3D composite structures. Existing literature highlights challenges related to lap joint manufacturing, notably the creation of resin-rich areas due to stitching and z-pinning methods, which lead to pockets of resin forming around 3D reinforcements. Furthermore, the insertion of 3D reinforcements, such as needles in stitching or pins in z-pinning, results in fibre misalignment within the lap joint structure. In contrast, tufting offers advantages like one-sided access, simplifying the manufacturing of 3D composites and expanding its applicability to both dry fibre and prepreg materials.

The research conducted here experimentally investigates the influence of tufting threads on lap joint performance, considering various manufacturing conditions and parameters such as off edge distance and tuft spacing. The study involved the manufacturing of lap joints using both dry fibre and prepreg materials. For dry fibre lap joints, an in-house solution was provided to facilitate the manufacturing process by placing fibre tows over the pin mold. Additionally, a specially designed and 3D-printed needle was used for the tufting process. The study evaluated the influence of tufting on lap joint performance under static loading conditions, including tensile and 3-point bending tests.

The study's experimental results revealed that tuft improved the lap shear strength of dry fibre lap joint and prepreg lap joint with respect to untufted lap joint up to 17% and 46% respectively. Similarly, for bending samples, strength of tufted lap joints were improved up to 36% and 20% for dry fibre lap joints and prepreg lap joint, respectively. The fractographic analysis revealed catastrophic failure for untufted and tufted in both dry fibre lap joints and prepreg lap joints. However, shear failure was dominant in all tufted cases, resulting in improving strength of lap joints. Microscopic examination indicated that failures in tufted lap joints initiated around the tufting thread in lap joint structures.