Papanicolaou George C, Portan Diana V, Kontaxis Lykourgos C
Composite Materials Group, Department of Mechanical Engineering and Aeronautics, University of Patras, 26500 Patras, Greece.
Polymers (Basel). 2021 Mar 23;13(6):978. doi: 10.3390/polym13060978.
The response of fiber-reinforced polymer composites to an externally applied mechanical excitation is closely related to the microscopic stress transfer mechanisms taking place in the fiber-matrix interphasial region. In particular, in the case of viscoelastic responses, these mechanisms are time dependent. Defining the interphase thickness as the maximum radial distance from the fiber surface where a specific matrix property is affected by the fiber presence, it is important to study its variation with time. In the present investigation, the stress relaxation behavior of a glass fiber-reinforced polymer (GFRP) under flexural conditions was studied. Next, applying the hybrid viscoelastic interphase model (HVIM), developed by the first author, the interphase modulus and interphase thickness were both evaluated, and their variation with time during the stress relaxation test was plotted. It was found that the interphase modulus decreases with the radial distance, being always higher than the bulk matrix modulus. In addition, the interphase thickness increases with time, showing that during stress relaxation, fiber-matrix debonding takes place. Finally, the effect of fiber interaction on the interphase modulus was found. It is observed that fiber interaction depends on both the fiber-matrix degree of adhesion as well as the fiber volume fraction and the time-dependent interphase modulus.
纤维增强聚合物复合材料对外加机械激励的响应与纤维-基体界面区域发生的微观应力传递机制密切相关。特别是在粘弹性响应的情况下，这些机制是随时间变化的。将界面厚度定义为从纤维表面起特定基体性能受纤维存在影响的最大径向距离，研究其随时间的变化很重要。在本研究中，研究了玻璃纤维增强聚合物（GFRP）在弯曲条件下的应力松弛行为。接下来，应用第一作者开发的混合粘弹性界面模型（HVIM），评估了界面模量和界面厚度，并绘制了它们在应力松弛试验期间随时间的变化曲线。结果发现，界面模量随径向距离减小，且始终高于基体本体模量。此外，界面厚度随时间增加，表明在应力松弛过程中发生了纤维-基体脱粘。最后，发现了纤维相互作用对界面模量的影响。观察到纤维相互作用既取决于纤维-基体的粘附程度，也取决于纤维体积分数和随时间变化的界面模量。
