Sustainability driven design of a recycled aircraft composite component

The thesis gives an extensive investigation in a PEKK/CF material rib (frame) structural aircraft part based on the reshaping property of thermoplastic composites according to sustainable design principles. In addition to mechanical performance values, economic, environmental footprint, and circularity requirements were incorporated in the design process, providing an integrated design approach. From a sustainability perspective, thermoplastics have been offered as a design-driven alternative to thermoset composites commonly used in aerospace, with their reshaping and recyclability characteristics.In the present work, a few thermal cycles (0–3 cycles) were applied to thermoplastic structural rib parts. Experimental test results were used as input to compare the mechanical performances of the cycles, while LCA and LCC values were used to provide data for environmental impact and cost comparison. The rib (frame) aircraft structural component was made of Toray Cetex TC1320 PEKK/CF-based, 14-ply [45, 0, 90, –45, 90, 0, 45]s laminated composite material. The parts were subsequently examined using non-destructive testing methods. Compressive modulus and compressive strength were quantified through the compression test (ASTM D6641/D3410) on specimens of exposed parts for different cycles (0–2 cycles). The degree of crystallinity was determined using differential scanning calorimetry (DSC); and thermal degradation and mass change quantities were determined using thermogravimetric analysis (TGA). The data collected were fed into the changing mechanical and material performance values of the TP material subjected to repeated cycles. In the sustainability analysis, Analytic Hierarchy Process (AHP) and TOPSIS approaches, two of the multi-criteria decision-making methods, were used. Sustainability analysis was calculated in this study based on ratings given by three expert participants. The maximum compressive force of the thermally untreated laminate plate sample was found to be 4660.4 N, compressive strength was 233.5 MPa, and chord modulus was 13.4 GPa. From the laminate plate to the 3rd cycle, the chord modulus increased by 58.9% from 13.4 GPa to 21.3 GPa, while the compressive force decreased by 7.8% to 4295.1 N, and parallel to this, the compressive strength decreased by the same amount to 214.7 MPa. The crystallinity was increased from 15,5% to the range of 20–23%; the initial decomposition temperature of TGA was decreased from 550 °C to 350 °C, and the cumulative mass loss was raised from 12,7% to 20,8%. During assessment of sustainability analysis, the TOPSIS closeness coefficients computed were derived as follows: TP (0th Cycle) 0,729, Thermoset (TS) 0,633, TP (1st Cycle) 0,485, TP (2 nd Cycle) 0,364. The increment in the crystallinity ratio with several cycles confirmed the growing trend in elastic modulus, whereas the effects introduced due to decreasing thermal stability and increasing microstructural damages were found to result in a reduction in strength. In the multi-criteria decision-making approach for the sustainability-oriented design analysis, comparison retained based on the methodology indicated that TP (0th Cycle) was the best alternative material. Thermoset (TS), TP (1 st Cycle), and TP (2 nd Cycle) materials followed the ranking.