Experimental and numerical study on failure mechanisms of sandwich composite structure: Effect of auxetic core

Sandwich composite structures are widely used in different applications due to their superior performances such as lightweight and high strength structure. This research presents a combination of experimental and numerical investigations of the compression strength of sandwich structures made from two types of cores (i.e., traditional hexagonal and auxetic re-entrant) with same skins. Both types of cores are produced from Nylon 12 using a 3D printing technique. Whereas, the skins of sandwich structures are made from glass/epoxy composite laminates using the vacuum bagging process. The study focuses on comparing the stress-strain plots, energy absorption, and deformation modes of two types of sandwich structures. Additionally, the specific energy absorption was calculated both per unit volume ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:msub> <mml:mi>W</mml:mi> <mml:mi>v</mml:mi> </mml:msub> </mml:math> ) and per unit mass ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mi>S</mml:mi> <mml:mi>E</mml:mi> <mml:mi>A</mml:mi> </mml:math> ), up to the point of densification. A strong correlation was observed between the experimental and numerical results based on the compressive strength-strain plots and the deformation modes. Findings show that the sandwich structure with the auxetic core sample can carry compressive strength double time than that of the hexagonal core. Furthermore, the out-of-plane energy absorption of the sandwich structure with the auxetic core sample outperformed that of the traditional one; making them potential structures for applications that required high mechanical performances.