Feasibility and performance evaluation of randomly oriented strand recycled composite skins in sandwich structures: A green cost-effective solution for aerospace secondary load-bearing applications

Despite the advantages of recycled randomly oriented strand (ROS) composites over recycled grinded ones, the warpage issue hinders their adaptation in the industry due to tolerance requirements. To address this challenge, ROS composites are incorporated into secondary bonded sandwich structures such that the core material ensures the straightness of the ROS composite skins. Additionally, atmospheric plasma activation (APA) is utilized to enhance the skin/core bonding to prevent skin separation under loading. The ROS composite skins are manufactured via vacuum-assisted hot press to achieve a cost-effective aerospace-grade quality. The structural integrity of the sandwich structure is assessed through flatwise tensile and edgewise compression tests, while the mechanical and thermomechanical performance is evaluated using flexural, impact, and dynamic mechanical analysis (DMA) tests. The flatwise tensile and edgewise compression tests confirm that APA effectively prevents core detachment, as evidenced by an average tensile strength of 2.28 MPa and an average compressive strength of 171.7 MPa. Moreover, the flexural and impact tests show that no premature skin failure occurs, supported by an average facing strength of 59.23 MPa in flexural testing and an average impact energy of 49.96 kJ/m(2). The DMA test indicates that most of the stiffness loss is due to the core material. This comprehensive analysis highlights recycled ROS composites as a sustainable and cost-effective alternative for quasi-isotropic skins in aerospace secondary load-bearing sandwich structures such as floors, doors, engine cowls, and spoilers.