Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 150448

150448 - Low Velocity Impact Responses of Auxetic and Non-Auxeitc Carbon Fiber Composites 

Carbon fiber composites are renowned for their exceptional mechanical properties for their exceptional mechanical properties, including high strength-to-weight ratios, excellent stiffness, and remarkable durability. However, since the only reinforcement in the out-of-plane direction for carbon fiber composites is the resin matrix that has a much lower strength than carbon fibers, making them susceptible to out-of-plane damage which could be caused by impact and indentation events. One way to improve the impact and indentation resistance for carbon fiber composites is to introduce auxeticity into carbon fiber composites. Producing auxetic carbon fiber composites with effective laminate-level negative Poisson’s ratios and have been reported to have enhancements on various mechanical properties of not only in impact and indentation resistance but also in fracture toughness, energy absorption capabilities and etc.

Auxeticity in carbon fiber composites can be achieved by tailoring the layup of an anisotropic composite laminate, which determines the anisotropy of individual constituent lamina and the strain mismatch between adjacent plies to achieve laminate-level negative Poisson’s ratios. In this study, we present out work on the low velocity impact responses of auxetic carbon fiber composites at elevating impact energy levels. These auxetic carbon fiber composites are specifically designed to produce laminate-level negative Poisson’s ratios in either in-plane or out-of-plane direction, equivalent non-auxetic laminates were selected by matching the effective moduli in the three principal directions. Low velocity impact tests were conducted for these auxetic and equivalent non-auxetic laminates according to ASTM D7136 standard at elevating impact energy levels. Post test damage characterizations were performed with non-destructive inspection methods of UT C-scan to capture the delamination damages, as well as with X-ray μCT to document other internal damage modes of fiber breakage and shear matrix cracking.  After that, compression after impact tests were performed to obtain the residual strength after impact of the tested specimens. The low velocity impact response of the auxetic laminates and the counterpart non-auxetic laminates were compared to investigate the role of auxeticity in affecting the damage low velocity impact damage behavior of carbon fiber composites. To better investigate the progressive damage evolution of the auxetic and non-auxetic laminates and observe their response to low velocity impacts, finite element analyses were performed with ABAQUS, the results in predicted delamination and matrix cracking damages are in good agreement with those observed with C-scan and X-ray μCT.

It was found that for both in-plane and out-of-plane auxetic laminates, the residual strengths after impact were higher than the respective equivalent non-auxetic laminates at impact energy levels of 5 and 25J, indicating strain rate sensitivity of the low velocity impact responses of carbon fiber composites. For the in-plane non-auxetic laminates, more severe shear matrix cracking and delamination damages towards the bottom interfaces away from the impact site can be observed in comparison with the in-plane auxetic laminates. Whereas for the out-of-plane auxetic and non-auxetic laminates, delamination damages were observed across all interfaces of the laminates with intensified delamination damages towards the bottom faces of the laminates. The results suggest that designing auxetic laminates with in-plane or out-of-plane negative Poisson’s ratios by simply tailoring the laminate layups can enhance the low velocity impact resistance as well as the residual strengths after impact of carbon fiber composites when comparing with conventional non-auxetic laminates.

Presenting Author: Wenhua Lin Syracuse University

Presenting Author Biography: Wenhua Lin is currently a PhD candidate in the Department of Mechanical and Aerospace Engineering at Syracuse University. Wenhua’s research focuses on the mechanics of carbon fiber reinforced composites subjected to various testing conditions, such as simulated lightning strike and low velocity hail impacts. His on-going research studies the mechanical response and failure mechanisms of auxetic carbon fiber reinforced composites under various mechanical loadings such as tension, uniaxial compressive buckling, indentation and impact.

Authors:

Wenhua Lin Syracuse University
Jason Mack University of Akron
Kwek Tze Tan University of Akron
Barry D. Davidson Syracuse University
Yeqing Wang Syracuse University