The dependency of the static residual tensile strength for the Glass Fiber-Reinforced Plastic (GFRP) laminates after impact on the impact energy level and indent shape is investigated. In this study, two different laminates, unidirectional, [0°₂]_s) and TRI (tri-axial, (±45°/0°)₂]_s), were prepared using the vacuum infusion method, and an impact indent on the respective laminates was created at different energy levels with pyramidal and hemispherical impactors. Impact damage patterns, such as matrix cracking, delamination, debonding and fiber breakage, could be observed on the GFRP laminates by a scanning electron microscope (SEM), and it is found that those were dependent on the impactor head shape and laminate structure. Residual in-plane tensile strength of the impacted laminates was measured and the reduction of the strength is found to be dependent upon the impact damage patterns. Furthermore, in this study, stress concentrations in the vicinity of the indents were determined from full-field stress distribution obtained by three-dimensional Digital Image Correlation (3D DIC) measurement. It was found that the stress concentration was associated with the reduction of the residual strength for the GFRP laminates.

中文翻译：

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GFRP复合材料层板在低速冲击下的静态残余拉伸强度响应

研究了玻璃纤维增​​强塑料（GFRP）层压板在冲击能级和压痕形状冲击后的静态残余拉伸强度的依赖性。在这项研究中，两个不同的层压板，单向[0° ₂ ] _s）和TRI（三轴（±45°/ 0°）₂ ] _s使用真空灌注法制备），并使用金字塔形和半球形冲击器在不同能级下在各个层压板上产生冲击凹痕。可以通过扫描电子显微镜（SEM）在GFRP层压板上观察到冲击破坏模式，例如基体开裂，分层，脱粘和纤维断裂，并且发现这些破坏模式取决于冲击头形状和层压结构。测量了冲击层压材料的残余面内拉伸强度，发现强度的降低取决于冲击损伤的方式。此外，在这项研究中，通过三维数字图像相关性（3D DIC）测量获得的全场应力分布来确定凹痕附近的应力集中。