Volume 29, Issue 5 (September 2001)
Stress Pattern Analysis by Thermal Emission of Plain Weave Carbon Fiber/Epoxy Resin Composite Iosipescu Specimens with Three Different Notch Angles
Iosipescu specimens were developed to examine the shear properties of isotropic materials. In the past decade, there has been much effort made to analyze this specimen configuration for measuring anisotropic materials, particularly laminated and woven composites. Some authors have used notch angles ranging from 90 to 110° in these materials and other authors have performed finite element analysis (FEA) to determine the notch angle and depth with the most uniform shear stress zone based on the elastic moduli. The object of this study was to verify the preferred angle of woven fiber composites through the use of stress pattern analysis by thermal emission (SPATE), which is a technique that can image the hydrostatic stress state in a material under load. SPATE images were collected for various specimens at different notch angles (90, 100, and 110°) and different weave lay ups. Mean load was held constant while the SPATE image was collected but later increased to examine the stress state of the Iosipescu specimens at high loads. The results indicate that for a plain woven carbon fiber/epoxy resin composite, the 100° notched specimen is the best specimen of the three conditions examined due to the delay in occurrence of damage and the large size of the pure shear zone.