Kötter Benedikt, Karsten Julian, Körbelin Johann, Fiedler Bodo
Institute of Polymer and Composites, Hamburg University of Technology, Denickestraße 15, 21073 Hamburg, Germany.
Materials (Basel). 2020 Feb 18;13(4):910. doi: 10.3390/ma13040910.
Thin-ply laminates exhibit a higher degree of freedom in design and altered failure behaviour, and therefore, an increased strength for unnotched laminates in comparison to thick-ply laminates. For notched laminates, the static strength is strongly decreased; this is caused by a lack of stress relaxation through damage, which leads to a higher stress concentration and premature, brittle failure. To overcome this behaviour and to use the advantage of thin-ply laminates in areas with high stress concentrations, we have investigated thin-ply hybrid laminates with different metal volume fractions. Open hole tensile (OHT) and open hole compression (OHC) tests were performed with quasi-isotropic carbon fibre reinforced plastic (CFRP) specimens. In the area of stress concentration, 90° layers were locally substituted by stainless steel layers of differing volume fractions, from 12.5% to 25%. The strain field on the specimen surface was evaluated in-situ using a digital image correlation (DIC) system. The embedding of stainless steel foils in thin-ply samples increases the OHT strength up to 60.44% compared to unmodified thin-ply laminates. The density specific OHT strength is increased by 33%. Thick-ply specimens achieve an OHC strength increase up to 45.7%, which corresponds to an increase in density specific strength of 32.4%.
薄铺层层压板在设计上具有更高的自由度且失效行为有所改变，因此，与厚铺层层压板相比，无缺口层压板的强度有所提高。对于有缺口的层压板，其静态强度会大幅降低；这是由于缺乏通过损伤实现的应力松弛，从而导致更高的应力集中和过早的脆性失效。为了克服这种行为并在高应力集中区域利用薄铺层层压板的优势，我们研究了具有不同金属体积分数的薄铺层混合层压板。对准各向同性碳纤维增强塑料（CFRP）试样进行了开孔拉伸（OHT）和开孔压缩（OHC）试验。在应力集中区域，90°层被体积分数从12.5%到25%不等的不锈钢层局部替代。使用数字图像相关（DIC）系统对试样表面的应变场进行了原位评估。与未改性的薄铺层层压板相比，在薄铺层样品中嵌入不锈钢箔可使OHT强度提高高达60.44%。密度比OHT强度提高了33%。厚铺层试样的OHC强度提高高达45.7%，这相当于密度比强度提高了32.4%。
