Session: 05-11-01: Multifunctional Composites and Structures: Mechanics, Modeling, and Space Applications

Paper Number: 149379

149379 - Design of Auxetic Composite Laminates: A Tradeoff Between Impact Resistance and Tensile Properties 

Carbon fiber reinforced polymer (CFRP) matrix composites are widely known to be highly tailorable. For instance, different laminate-level mechanical properties for CFRP composites can be achieved by varying the individual carbon fiber laminar arrangements, among one of them is the Poisson’s ratio. Negative Poisson's ratio (NPR) can be produced in CFRP composites at the laminate level, making them auxetic laminates. Materials with NPRs have been shown to improve the indentation and impact resistances, when compared to equivalent materials with positive Poisson's ratio (PPRs). Auxetic CFRP composite laminates were also shown to have varying degrees of enhancement in these resistances when compared to their non-auxetic counterparts. However, producing NPRs could potentially compromise other properties, such as tensile properties, which has not been reported.

In this presentation, I will first present our results on the enhacement of low velocity impact resistances in CFRP composites that are designed with auxetic layups. Both auxetic laminates with in-plane NPR and those with through-thickness NPR are investigated. Specifically, it was found that through-thickness auxetic laminate showed consistently smaller matrix tensile damage at all plies and all investigated impact energies. Moreover, they showed consistently smaller fiber tensile damage at all plies under higher impact energy of 8J. The in-plane auxetic laminate exhibited smaller delamination area on top and bottom interfaces, especially at higher impact energies. They also showed smaller fiber tensile damage at all plies under impact energy of 8J. Then, I will discuss the compromise in tensile properties in auxetic CFRP composites with both experimental and FEA simulation results. Specifically, to understand the role of NPR in the tensile failure of the auxetic CFRP composites, the predictions of the failure strains from FEA and classical classical lamination theory (CLT) were compared with the experimental data. Moreover, the predicted strain field was compared with the strain field obtained using digital image correlation in the experimental tests. Such comparisons allow us to investigate whether the NPR plays a role in locally changing the strain field and hence making the conventional CLT and failure criteria (e.g., maximum strain failure criterion) invalid. It was found that the special layups that are required to produce auxetic laminates could render lower ultimate failure strain of the laminate hence lower ultimate tensile strength, considerations are to be given whether improvement in impact resistances outweigh the reduction in tensile properties in the case of auxetic laminates.

The results are expected to provide guidance in exploiting NPR for designing multifunctional composite structures, specifically for impact critical applications.

Presenting Author: Yeqing Wang Syracuse University

Presenting Author Biography: Dr. Yeqing Wang is currently an assistant professor at the Department of Mechanical and Aerospace Engineering at Syracuse University. His research interests include mechanics of composite materials and structures, multifunctional composites, advanced manufacturing of composite materials, and lightning strike protection of composites. He is a recipient of the Ralph E. Powe Junior Faculty Enhancement Award and the Best Paper Award at the 2012 American Society for Composites Technical Conference, a voted member of the ASME Structures & Materials Technical Committee, and a senior member of AIAA.

Authors:

Wenhua Lin Syracuse University
Yeqing Wang Syracuse University