Osa-Uwagboe Norman, Udu Amadi Gabriel, Silberschmidt Vadim V, Baxevanakis Konstantinos P, Demirci Emrah
Wolfson School of Mechanical, Electrical, and Manufacturing Engineering, Loughborough University, Loughborough LE11 3TU, UK.
Air Force Research and Development Centre, Nigerian Air Force Base, Kaduna 800282, Nigeria.
Materials (Basel). 2023 Jul 17;16(14):5036. doi: 10.3390/ma16145036.
The use of fibre-reinforced plastics (FRPs) in various industrial applications continues to increase thanks to their good strength-to-weight ratio and impact resistance, as well as the high strength that provides engineers with advanced options for the design of modern structures subjected to a variety of out-of-plane impacts. An assessment of the damage morphology under such conditions using non-destructive techniques could provide useful data for material design and optimisation. This study investigated the damage mechanism and energy-absorption characteristics of E-glass laminates and sandwich structures with GFRP face sheets with PVC cores under quasi-static indentation with conical, square, and hemispherical indenters. An acoustic emission (AE) technique, coupled with a k-means++ pattern-recognition algorithm, was employed to identify the dominant microscopic and macroscopic damage mechanisms. Additionally, a post-mortem damage assessment was performed with X-ray micro computed tomography and scanning electron microscopy to validate the identified clusters. It was found that the specific energy absorption after impact with the square and hemispherical indenters of the GFRP sandwich and the plain laminate differed significantly, by 19.29% and 43.33%, respectively, while a minimal difference of 3.5% was recorded for the conical indenter. Additionally, the results obtained with the clustering technique applied to the acoustic emission signals detected the main damaged modes, such as matrix cracking, fibre/matrix debonding, delamination, the debonding of face sheets/core, and core failure. The results therefore could provide a methodology for the optimisation and prediction of damage for the health monitoring of composites.
由于纤维增强塑料（FRP）具有良好的强度重量比和抗冲击性，以及其高强度为工程师在设计承受各种面外冲击的现代结构时提供了先进的选择，因此其在各种工业应用中的使用量持续增加。使用无损技术评估在这种条件下的损伤形态可为材料设计和优化提供有用的数据。本研究调查了具有PVC芯的GFRP面板E玻璃层压板和夹层结构在锥形、方形和半球形压头准静态压痕下的损伤机制和能量吸收特性。采用声发射（AE）技术并结合k均值++模式识别算法来识别主要的微观和宏观损伤机制。此外，还使用X射线微计算机断层扫描和扫描电子显微镜进行了事后损伤评估，以验证所识别的聚类。结果发现，GFRP夹层板和平板层压板在受到方形和半球形压头冲击后的比能量吸收分别有显著差异，相差19.29%和43.33%，而对于锥形压头，记录的最小差异为3.5%。此外，将聚类技术应用于声发射信号所获得的结果检测到了主要的损伤模式，如基体开裂、纤维/基体脱粘、分层、面板/芯脱粘和芯失效。因此，这些结果可为复合材料健康监测的损伤优化和预测提供一种方法。
