Effect of drilling induced defects on the mechanical properties of carbon fiber-reinforced thermoplastic polyamide

The files represent the result for the flexural and tensile tests. The initial state as well as two different drill hole qualities were examined. The quasi-static experiments of the undrilled / drilled specimens were carried out on an universal testing machine. The 5.9 mm diameter holes were made in the center of gravity. Ultimate tensile (UTS), open-hole tensile (OHT) and ultimate flexural (UFS), open-hole flexural (OHF) strengths and the load progression were determined for at least five individual test specimens. The test set-up for the 4-point flexural tests were adapted from ISO 14125. The corresponding set-up for the tensile tests was in accordance to ISO 527-4. Both test set-ups are describe in detail in the manuscript.
A first key finding is that the drill hole quality has neither a critical influence onto the fiber dominated strength under tensile load nor onto the matrix dominated flexural strength. Both drill hole qualities led to about the same decrease of the particular strength value in comparison with the undrilled specimens. Therefore one can say, that the borehole itself is by far the most strength limiting factor, whereas the machining quality seems to be minor relevant for the strength behavior in drilled thermoplastic CFRP laminates under static loading.
A second key finding is that the detected strength degradation induced by a 5.9 mm borehole was significantly higher under 4-point flexural loading (14%) compared to the 8 % under tensile loading. This shows, that tests under 4-point flexural load have a greater influence on the mechanical properties of drilled CFRTP than under tensile load.

本数据集文件包含弯曲与拉伸试验的测试结果。本研究对试样的初始状态以及两种不同的钻孔加工质量开展了测试分析。未钻孔及已钻孔试样的准静态试验均在万能试验机上完成。钻孔直径为5.9mm，加工于试样的重心位置。本研究至少对5个独立试样进行了测试，得到了抗拉强度极限（Ultimate Tensile Strength, UTS）、开孔拉伸强度（Open-hole Tensile, OHT）、弯曲强度极限（Ultimate Flexural Strength, UFS）、开孔弯曲强度（Open-hole Flexural, OHF）以及载荷变化历程。四点弯曲试验的测试装置参考ISO 14125标准搭建；拉伸试验的测试装置则符合ISO 527-4标准要求。两种试验装置的详细设置均已在研究手稿中予以说明。

第一项核心研究结果表明：钻孔加工质量对拉伸载荷下的纤维主导型强度，以及弯曲载荷下的基体主导型强度均无显著影响。相较于未钻孔试样，两种钻孔加工方案均使试样的对应强度值出现了相近幅度的下降。因此可以认为，钻孔本身是限制强度的最主要因素，而加工质量对静态载荷下钻孔热塑性碳纤维增强复合材料（Carbon Fiber Reinforced Thermoplastic, CFRTP）层合板的强度性能影响极小。

第二项核心研究结果显示：相较于拉伸载荷下8%的强度退化幅度，5.9mm钻孔在四点弯曲载荷下引发的强度退化程度显著更高（达14%）。这表明，相较于拉伸试验，四点弯曲载荷试验对钻孔CFRTP试样的力学性能影响更为显著。