Open-hole tension test reveals the effect of a circular hole on laminate strength and stress concentration.

• A. Fiber tensile strength
• B. Effect of a circular hole on laminate strength and stress concentration
• C. Thermal conductivity
• D. Interlaminar shear strength

Answer: (B)

Open-hole tension tests are used to see how a circular hole changes the way a laminated composite carries load. The hole removes material and forces the in-plane stresses to flow around its edge, creating a concentration of stress that is higher than the nominal far from the hole. In composites, the way this stress concentrates depends on the layup and fiber directions, so the test reveals how the laminate’s strength is reduced by the hole and how severe the concentration is. This information is crucial for designing fastener holes and predicting failure around them.

This is not about the inherent tensile strength of the fibers themselves, nor about thermal conductivity, nor primarily about the interlaminar shear strength. Those properties pertain to different aspects of material behavior, while the open-hole tension test targets the hole’s impact on laminate strength and the resulting stress concentration.