Debonding at the core–skin interphase region is one of the primary failure modes in core sandwich composites under shear loads. As a result, the ability to characterize the mechanical properties at the interphase region between the composite skin and core is critical for design analysis. This work intends to use nanoindentation to characterize the viscoelastic properties at the interphase region, which can potentially have mechanical properties changing from the composite skin to the core. A sandwich composite using a polyvinyl chloride foam core covered with glass fiber/resin composite skins was prepared by vacuum-assisted resin transfer molding. Nanoindentation at an array of sites was made by a Berkovich nanoindenter tip. The recorded nanoindentation load and depth as a function of time were analyzed using viscoelastic analysis. Results are reported for the shear creep compliance and Young’s relaxation modulus at various locations of the interphase region. The change of viscoelastic properties from higher values close to the fiber composite skin region to the smaller values close to the foam core was captured. The Young’s modulus at a given strain rate, which is also equal to the time-averaged Young’s modulus across the interphase region was obtained. The interphase Young’s modulus at a loading rate of 1 mN s⁻¹ was determined to change from 1.4 GPa close to composite skin to 0.8 GPa close to the core. This work demonstrated the feasibility and effectiveness of nanoindentation-based interphase characterizations to be used as an input for the interphase stress distribution calculations, which can eventually enrich the design process of such sandwich composites.

芯-皮相间区域的剥离是剪切载荷下芯夹芯复合材料的主要破坏模式之一。结果，表征复合皮层和芯部之间的相间区域的机械性能的能力对于设计分析至关重要。这项工作旨在使用纳米压痕来表征相间区域的粘弹性，这些黏弹性可能具有从复合表层到核心的机械性能变化。通过真空辅助树脂传递模塑法制备使用覆盖有玻璃纤维/树脂复合材料表皮的聚氯乙烯泡沫芯的三明治复合材料。通过Berkovich纳米压痕头在一系列位点进行纳米压痕。使用粘弹性分析法分析记录的纳米压痕载荷和深度随时间的变化。报告了相间区域各个位置处的剪切蠕变柔度和杨氏松弛模量的结果。捕获了粘弹性的变化，从接近纤维复合材料表皮区域的较高值到接近泡沫芯的较小值。在给定的应变速率下获得了杨氏模量，该杨氏模量也等于整个相间区域的时间平均杨氏模量。加载速率为1 mN s时的相间杨氏模量 它也等于整个相间区域的时间平均杨氏模量。加载速率为1 mN s时的相间杨氏模量 它也等于整个相间区域的时间平均杨氏模量。加载速率为1 mN s时的相间杨氏模量^-1被确定为从接近复合表皮的1.4 GPa变为接近核心的0.8 GPa。这项工作证明了基于纳米压痕的相间表征作为相间应力分布计算输入的可行性和有效性，最终可以丰富此类夹心复合材料的设计过程。