Pitta Siddharth, Roure Francesc, Crespo Daniel, Rojas Jose I
Department of Physics-Division of Aerospace Engineering, Universitat Politècnica de Catalunya, c/ Esteve Terradas 7, 08860 Castelldefels, Spain.
Department of Strength of Materials and Structural Engineering, Universitat Politècnica de Catalunya, av. Diagonal 647, 08028 Barcelona, Spain.
Materials (Basel). 2019 Sep 14;12(18):2978. doi: 10.3390/ma12182978.
In this work, experimental and numerical analyses of repairs on carbon fiber reinforced epoxy (CFRE) substrates, with CFRE and aluminum alloy doublers typical of aircraft structures, are presented. The substrates have a bridge gap of 12.7 mm (simulated crack), repaired with twin doublers joined with riveted, adhesive bonded, and hybrid joints. The performance of the repairs using different doubler materials and joining techniques are compared under static loading. The experimental results show that riveted joints have the lowest strength, while adhesive bonded joints have the highest strength, irrespective of the doubler material. Finite element analysis (FEA) of the studied joints is also performed using commercial FEA tool Abaqus. In the FEA model, point-based fasteners are used for the rivets, and a cohesive zone contact model is used to simulate the adhesive bond. The FEA results indicate that the riveted joints have higher tensile stresses on the metal doublers compared to the composite doublers. As per the failure modes, interestingly, for hybrid joints using composite doublers, the doublers fail due to net-section failure, while, for hybrid joints using metal doublers, it is the composite substrate that fails due to net-section failure. This suggests vulnerability of the composite structures to mechanical fastener holes. Lastly, the Autodesk Helius composite tool is used for prediction of first-ply failure and ply load distribution, and for progressive failure analysis of the composite substrate.
在这项工作中，对碳纤维增强环氧树脂（CFRE）基材的修复进行了实验和数值分析，修复采用了飞机结构中典型的CFRE和铝合金加强板。基材有一个12.7毫米的桥接间隙（模拟裂纹），用通过铆接、粘结和混合连接方式连接的双加强板进行修复。在静态载荷下比较了使用不同加强板材料和连接技术的修复性能。实验结果表明，无论加强板材料如何，铆接接头强度最低，而粘结接头强度最高。还使用商业有限元分析工具Abaqus对所研究的接头进行了有限元分析（FEA）。在有限元分析模型中，铆钉采用基于点的紧固件，粘结采用粘结区接触模型进行模拟。有限元分析结果表明，与复合材料加强板相比，铆接接头在金属加强板上的拉应力更高。有趣的是，就失效模式而言，对于使用复合材料加强板的混合接头，加强板因净截面失效而破坏，而对于使用金属加强板的混合接头，是复合材料基材因净截面失效而破坏。这表明复合材料结构对机械紧固件孔的脆弱性。最后，使用Autodesk Helius复合材料工具预测第一层失效和层载荷分布，并对复合材料基材进行渐进失效分析。
