Reinforcing Shape Memory Polymers With Reclaimed Carbon Fibers: Toward Sustainable and Functional Smart Composites

The study focuses on recycled carbon fibers that are usually recovered as short, randomly oriented pieces and therefore limited to lower-value uses. It explores whether these reclaimed fibers can be turned into higher-value smart materials by reinforcing shape-memory polymers (SMPs). SMP composites were made with reclaimed carbon fibers of two lengths (0.5 mm and 4 mm) and different fiber loadings (0–3 wt.%). The composites were tested for tensile performance and for how quickly they respond to different activation methods, including thermal radiation, hot-water exposure, and electro-activation. The results show that adding reclaimed carbon fibers improves mechanical properties, with 4 mm fibers giving the highest strength and modulus. Fiber content also affects heating behavior: at 2 wt.% the heating rate to the glass transition temperature (~52°C) increases and the full recovery time decreases, while higher loading (3 wt.%) improves temperature uniformity with a slightly lower heating rate. For activation, hot-water exposure enabled complete recovery within 10 seconds for all samples. Electro-activation showed a strong dependence on fiber length: only composites with 4 mm fibers formed conductive networks that achieved full recovery within 20 seconds.