Abstract
In this study, a total of 30 3D re-entrant honeycomb specimens made of polyamide were fabricated with various configurations by using the additive manufacturing (AM) technique. Split Hopkinson Pressure Bar (SHPB) tests were conducted on the RH specimens at different impact velocities. The incident, reflected and transmitted waveforms can well explain the wave propagation and energy absorption characteristics of the specimens, which can help us to understand and analyse the process of impact loading. The stress–strain curves, energy absorption ability and failure modes of SHPB tests with different impact velocities and quasi-static compression tests were analysed and compared, and it was found that the flow stress and energy absorption ability of the specimens subjected to impact load were much improved. Among the tested specimens, specimen C2, with a smaller re-entrant angle θ, displayed the best energy absorption ability, which was 1.701 J/cm3 at the impact velocity of 22 m/s and was 5.1 times that in the quasi-static test. Specimen C5 had the longest horizontal length of the diagonal bar L0, and its energy absorption was 1.222 J/cm3 at the impact velocity of 22 m/s and was 15.7 times that in the quasi-static test, reflecting the superiority of a structurally stable specimen in energy absorption under impact loading. The test results can provide a reference for the optimization of the design of the same or similar structures.
Highlights
Both auxetic materials and structures exhibit the characteristic of a negative Poisson’s ratio, expanding in the lateral direction when stretched and contracting when compressed, which is contrary to the positive Poisson’s ratio properties of general materials and structures and is known as auxetic behaviour
Rad et al [11] dealt with the calculation of the basic mechanical properties of re-entrant honeycomb (RH)
It is worth noting that this paper mainly studies the impact behaviour of the 3D RH structure, rather than the dynamic testing process and data processing of the polymethyl methacrylate (PMMA) bar
Summary
Both auxetic materials and structures exhibit the characteristic of a negative Poisson’s ratio, expanding in the lateral direction when stretched and contracting when compressed, which is contrary to the positive Poisson’s ratio properties of general materials and structures and is known as auxetic behaviour. Due to the auxetic characteristic, it has some excellent properties, such as increased shear modulus [3,4], increased indentation resistance [3,5], high fracture toughness [6,7], high energy absorption [8,9] and unique acoustic absorption [10]. It is widely used in aerospace, protection, biomedicine, manufacturing, sports, sensors and other fields [1]. Rad et al [11] dealt with the calculation of the basic mechanical properties of RH structures by using the energy methods of solid mechanics along with numerical methods
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
