Elmahdy Ahmed, Zotti Aldobenedetto, Borriello Anna, Zarrelli Mauro, Verleysen Patricia
Materials Science and Technology-DyMaLab Research Group, Department of Electromechanical Systems and Metals Engineering, Faculty of Engineering and Architecture, Ghent University, Tech Lane Ghent Science Park, Technologiepark 46, 9052 Zwijnaarde, Belgium.
Institute of Polymers, Composites and Biomaterials, National Research Council of Italy, P.Ie Fermi, 1, 80055 Portici, Naples, Italy.
Polymers (Basel). 2022 Apr 27;14(9):1771. doi: 10.3390/polym14091771.
The aim of this paper is to study the effect of strain rate on the compressive behavior of the highly cross-linked RTM6 epoxy resin used in advanced aerospace composites. Dynamic compression tests were performed using a split Hopkinson pressure bar, along with reference quasi-static compression tests, to cover a strain rate range from 0.001 to 1035 s. Special attention was paid to the optimization of the test methodologies in order to obtain material data free of bias related to the use of different load introduction techniques and sample geometries over the considered strain rate range. In addition, the use of full-field 3D deformation measurements allowed the validation of traditional test and material assumptions. A novel self-alignment tool was developed to enable perfect interfacial contact during compression loading. The 3D digital image correlation technique was used to measure the instantaneous deformation of the sample during compression at different strain rates. Results showed a pronounced strain rate sensitivity of the RTM6 epoxy in compression. The peak yield strength increased with increasing strain rate, while the elastic modulus and Poisson's ratio in compression were independent of the strain rate. The barreling of the sample in compression, quantified by the barreling ratio, showed an increase during the progression of the compression tests. However, the barreling ratio significantly decreased with the increasing strain rate. Finally, it was shown that neglecting the significant volume change in the yield stages gave rise to a non-negligible underestimation of the strength of the material.
本文旨在研究应变速率对先进航空航天复合材料中使用的高度交联RTM6环氧树脂压缩行为的影响。使用分离式霍普金森压杆进行动态压缩试验，并结合参考准静态压缩试验，以覆盖从0.001至1035 s的应变速率范围。特别关注试验方法的优化，以便在考虑的应变速率范围内获得与使用不同载荷引入技术和样品几何形状无关的无偏差材料数据。此外，使用全场三维变形测量能够验证传统试验和材料假设。开发了一种新型自对准工具，以在压缩加载过程中实现完美的界面接触。采用三维数字图像相关技术测量样品在不同应变速率压缩过程中的瞬时变形。结果表明，RTM6环氧树脂在压缩时具有明显的应变速率敏感性。峰值屈服强度随应变速率的增加而增加，而压缩时的弹性模量和泊松比与应变速率无关。通过鼓胀比量化的样品压缩鼓胀在压缩试验过程中呈现增加趋势。然而，鼓胀比随应变速率的增加而显著降低。最后，结果表明，忽略屈服阶段的显著体积变化会导致对材料强度的不可忽略的低估。
