The aim of the study is to investigate the physico-mechanical and flammability performance of a 3D-printed functionally graded composite (FGC) developed using iterated layer deposition of polyamide-carbon fibre (PA-CF) and polyamide-glass fibre (PA-GF) composite. The samples were fabricated with varying PA-CF and PA-GF iteration layers, starting with a unary layer (1 layer) and ending with a quaternion layer (4 layers). The shore D hardness and shrinkage test revealed that samples with 1 and 2 iterations of PA-CF and PA-GF layers exhibited the highest hardness of 71.3 ± 2 SHD and 71 ± 1.8 SHD, respectively, with the lowest shrinkage of 11.9 ± 1.01% and 11.9 ± 0.8%, respectively. Similarly, the same FGC exhibited the highest flexural stress (F s ) 31.2 ± 1.4 MPa and 32.9 ± 1.5 MPa and ultimate tensile stress (UTS) values of 28.70 ± 1.0 MPa and 27.37 ± 0.4 MPa, respectively. The selection of up to 3 iteratively applied layers of PA-CF and PA-GF was found to be optimal for developing FGC. The flammability analysis revealed that all the samples exhibited an HB rating, indicating comparable baseline flammability behaviour. Based on the obtained response, the study successfully addresses the existing research gap in PA-based multi-fibre 3D printing by systematically correlating the layer alternation strategy with interfacial performance and structural efficiency. The developed composite has strong potential for lightweight semi-structural applications, such as UAV structures, automobile interiors, customized tools, and load-bearing fixtures.
Kannan et al. (Fri,) studied this question.