A study of the penetration behavior of bio-inspired CFRP composite laminates with intralaminar and interlaminar hard-and-soft structures

Novel and cost-effective bio-inspired composite laminates, including hard and soft structures, were designed to improve impact resistance. The regular hexagonal TPU frames and TPU film interleaves were inserted into carbon fabrics and interface as intralaminar and interlaminar soft phases. The impact response and material damage influenced by intralaminar and interlaminar TPU were investigated separately through low-velocity impact. Experimental results show penetration energy for the laminates with TPU soft phase was significantly enhanced, with the value of 5 J, 12.5 J, and 10 J for type A, B, and C, respectively, in which the type B with TPU films inserted between layers has the maximum increase percentage by 38 %. Thus, TPU interleaves can improve penetration energy more effectively than the intralaminar TPU phase. Failure is divided into three categories including no penetration, tough penetration, and brittle penetration, as characterized by different failure modes. Interestingly, the laminates with TPU phase displayed tough penetration while baselines without TPU can only present brittle penetration with even more fabrics included. Permanent deformation was observed for specimens with TPU phase after penetration instead of obvious delamination and fiber bundle breakage appeared in baselines. In general, hard and soft strategies with TPU phase can prevent sudden catastrophic failure under high-energy impact. This study demonstrates the important influence of soft phase, provides cost-effective strategies of improving impact resistance for composite laminates, and acquires a deeper understanding of penetration failure modes and mechanisms.