An open-hole compression test method has been developed to assess the notch sensitivity of sandwich composites under compression loading. This test method, in the process of being standardized by ASTM International, utilizes end loading as well as knife-edge side supports to provide out-of-plane restraint to specimen buckling. Finite element analyses focused on identifying a sandwich specimen geometry that minimized finite-width and finite-length effects on the stress concentration produced by the centrally-located through-hole. Geometric variables included the specimen width-to-hole diameter (w/D) and length-to-hole diameter (l/D) ratios. The sandwich configurations investigated consisted of a Nomex honeycomb core and carbon/epoxy facesheet laminates with a range of material orthotropy ratios. Numerical results were used to identify a candidate sandwich specimen geometry and optimal strain gage placements for use in specimen alignment. A series of mechanical tests were performed to evaluate the proposed specimen design, the proposed test fixture, and the recommended test procedure. The first set of experiments were performed using specimens with different hole diameters but the same specimen width and length. A second set of experiments used specimens with different lengths but with the same specimen width and open-hole. In addition, the use of specimen end potting of the core region was investigated to prevent facesheet separation and end brooming.

已经开发了一种开孔压缩测试方法来评估夹层复合材料在压缩载荷下的缺口敏感性。该测试方法在由 ASTM International 标准化的过程中，利用端部载荷和刀刃侧支撑来为试样屈曲提供平面外约束。有限元分析侧重于识别夹层试样几何形状，该几何形状使有限宽度和有限长度对中心通孔产生的应力集中的影响最小化。几何变量包括样品宽度与孔的直径 (w/D) 和长度与孔的直径 (l/D) 的比率。研究的夹层结构由 Nomex 蜂窝芯和碳/环氧树脂面板层压板组成，具有一系列材料正交各向异性比。数值结果用于确定候选夹层试样几何形状和用于试样对齐的最佳应变计放置。进行了一系列机械测试以评估建议的试样设计、建议的测试夹具和推荐的测试程序。第一组实验是使用具有不同孔径但试样宽度和长度相同的试样进行的。第二组实验使用不同长度但具有相同宽度和开孔的试样。此外，还研究了使用芯部区域的样品端部灌封来防止面板分离和端部清扫。建议的测试夹具和建议的测试程序。第一组实验是使用具有不同孔径但试样宽度和长度相同的试样进行的。第二组实验使用不同长度但具有相同宽度和开孔的试样。此外，还研究了使用芯部区域的样品端部灌封来防止面板分离和端部清扫。建议的测试夹具和建议的测试程序。第一组实验是使用具有不同孔径但试样宽度和长度相同的试样进行的。第二组实验使用不同长度但具有相同宽度和开孔的试样。此外，还研究了使用芯部区域的样品端部灌封来防止面板分离和端部清扫。