Mechanical properties of novel uniform/gradient auxetic structures made of CFRP composites

Abstract

Carbon fiber reinforced polymer (CFRP) auxetic composite structures have attracted an increasing attention in recent years due to their lightweight and superior mechanical properties compared with traditional auxetic structures. However, most of the reported all-CFRP auxetic structures are often accompanied with cliff-like stress drops during the failure process, resulting in lower energy absorption. This paper reports the design, fabrication and characterization of a novel type of all-CFRP petal-like auxetic structures with lightweight, high-strength, and good energy absorptive properties. Four uniform/gradient petal-like structures were first made with different angle values and continuous CFRP composites. Then, their mechanical properties, Poisson's ratio and failure mechanism under quasi-static compression loading were analyzed. Based on the quasi-static experimental results, the gradient structure constructed with different cells of varying angles was further selected to study its dynamic response under different initial impact energies and impact positions. The results show that the novel petal-like structures made of continuous CFRP composites can maintain good auxetic properties even under large deformation. Impressively, these structures exhibit a stress plateau phase during compression, indicative of exceptional energy absorption capabilities. The results of low velocity point impact tests also show that the displacement of the initial peak and the number of peaks in the load–displacement curves are significantly influenced by changes in impact position and energy. This research offers a valuable insight into developing and fabricating all-CFRP auxetic structures with superior energy absorption characteristics. Highlights: Auxetic structures with high EA capacity are designed and fabricated. Their mechanical properties under static and dynamic loads are studied. The position and energy of impact have a significant impact on performance. The all-CFRP auxetic structure exhibits abundant failure forms.