Tailored continuous flax fiber-reinforced shape memory polymer biocomposites: Enhanced thermomechanical and shape memory performance for sustainable structural applications
Asmaa Hassan, Hanaa Dahy
Abstract
Shape memory polymer composites (SMPCs) reinforced with continuous fibers offer superior thermomechanical properties compared to pure shape memory polymers (SMPs), making them ideal for structural and architectural applications. While most SMPCs use synthetic fibers, natural fibers like flax offer a sustainable and viable alternative. However, existing SMPCs primarily use fiber fabrics, which restricts control over fiber alignment. This study investigates a novel, eco-friendly biocomposite: continuous flax fiber yarn-reinforced epoxy-SMP biocomposites (SMPBC), leveraging tailored fiber placement (TFP) for precise fiber alignment. SMPBCs with three fiber orientations (0°, 45°, and 90°) were analyzed for their thermomechanical properties, shape memory behavior, and durability after repeated cycles. Performance was assessed using dynamic mechanical analysis (DMA), tensile, flexural, and fold-deploy tests. Results showed that fiber orientation significantly influenced both mechanical and shape memory properties. The 0° SMPBCs exhibited the highest tensile and flexural strength, increasing by 570% and 370% compared to SMP, but had the lowest shape recovery (R r ) at 88%. Meanwhile, 90° SMPBCs achieved nearly 100% Rr but had the weakest mechanical properties. The 45° SMPBC demonstrated a balanced performance, improving tensile and flexural strength by 170% and 150%, while maintaining a high R r (96%). All SMPBCs exhibited high shape fixity (∼100%). Comparisons with existing composites highlight SMPBCs’ competitive performance. Potential architectural applications were explored, and further optimization strategies, driven by structural simulations, were introduced. Additionally, electroactive SMPBCs were developed. The findings demonstrate superior mechanical and shape memory performance, underscoring SMPBCs’ potential as sustainable, high-performance materials for self-adaptive and self-shaping architectural and structural applications.