Spinelli Giovanni, Guarini Rosella, Ivanov Evgeni, Calabrese Elisa, Raimondo Marialuigia, Longo Raffaele, Guadagno Liberata, Vertuccio Luigi
Faculty of Transport Sciences and Technologies, University of Study "Giustino Fortunato", Via Raffaele Delcogliano 12, 82100 Benevento, Italy.
Open Laboratory on Experimental Micro and Nano Mechanics, Institute of Mechanics, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Block 4, 1113 Sofia, Bulgaria.
Polymers (Basel). 2024 Jun 28;16(13):1849. doi: 10.3390/polym16131849.
In recent years, self-healing polymers have emerged as a topic of considerable interest owing to their capability to partially restore material properties and thereby extend the product's lifespan. The main purpose of this study is to investigate the nanoindentation response in terms of hardness, reduced modulus, contact depth, and coefficient of friction of a self-healing resin developed for use in aeronautical and aerospace contexts. To achieve this, the bifunctional epoxy precursor underwent tailored functionalization to improve its toughness, facilitating effective compatibilization with a rubber phase dispersed within the host epoxy resin. This approach aimed to highlight the significant impact of the quantity and distribution of rubber domains within the resin on enhancing its mechanical properties. The main results are that pure resin (EP sample) exhibits a higher hardness (about 36.7% more) and reduced modulus (about 7% more), consequently leading to a lower contact depth and coefficient of friction (11.4% less) compared to other formulations that, conversely, are well-suited for preserving damage from mechanical stresses due to their capabilities in absorbing mechanical energy. Furthermore, finite element method (FEM) simulations of the nanoindentation process were conducted. The numerical results were meticulously compared with experimental data, demonstrating good agreement. The simulation study confirms that the EP sample with higher hardness and reduced modulus shows less penetration depth under the same applied load with respect to the other analyzed samples. Values of 877 nm (close to the experimental result of 876.1 nm) and 1010 nm (close to the experimental result of 1008.8 nm) were calculated for EP and the toughened self-healing sample (EP-R-160-T), respectively. The numerical results of the hardness provide a value of 0.42 GPa and 0.32 GPa for EP and EP-R-160-T, respectively, which match the experimental data of 0.41 GPa and 0.30 GPa. This validation of the FEM model underscores its efficacy in predicting the mechanical behavior of nanocomposite materials under nanoindentation. The proposed investigation aims to contribute knowledge and optimization tips about self-healing resins.
近年来，自修复聚合物因其能够部分恢复材料性能从而延长产品使用寿命而成为一个备受关注的话题。本研究的主要目的是研究一种为航空航天领域开发的自修复树脂在硬度、折合模量、接触深度和摩擦系数方面的纳米压痕响应。为实现这一目标，对双官能环氧前驱体进行了定制功能化处理，以提高其韧性，促进与分散在主体环氧树脂中的橡胶相有效相容。这种方法旨在突出树脂中橡胶域的数量和分布对增强其机械性能的重大影响。主要结果是，与其他配方相比，纯树脂（EP样品）表现出更高的硬度（约高36.7%）和折合模量（约高7%），因此导致更低的接触深度和摩擦系数（低11.4%），而其他配方则相反，由于其吸收机械能的能力，更适合于保护免受机械应力的损伤。此外，还进行了纳米压痕过程的有限元方法（FEM）模拟。将数值结果与实验数据进行了细致比较，结果显示吻合良好。模拟研究证实，在相同的加载条件下，硬度和折合模量较高的EP样品相对于其他分析样品的穿透深度更小。EP和增韧自修复样品（EP-R-160-T）的计算值分别为877 nm（接近实验结果876.1 nm）和1010 nm（接近实验结果1008.8 nm）。硬度的数值结果显示，EP和EP-R-160-T的硬度分别为0.42 GPa和0.32 GPa，与实验数据0.41 GPa和0.30 GPa相符。有限元模型的这种验证突出了其在预测纳米复合材料在纳米压痕下机械行为方面的有效性。所提出的研究旨在提供有关自修复树脂的知识和优化建议。
