A short-beam shear fracture approach to measure the mode II fracture toughness of materials with preferred interfaces

Abstract

A short-beam shear fracture approach is developed to characterize the mode II fracture toughness, (K IIC ) of materials with preferred interfaces such as wood, fiber composite materials and bonded materials. This approach is easy to implement using the Iosipescu shear fixture and is free of friction between the cracked faces thereby offering a more reasonable value of K IIC than previous methods. Another feature of our new approach is the measurement of accurate crack initiation load due to a clear load drop. Additionally, calibration charts for bonded polymers and composite materials are generated. Finite element analysis along with cohesive elements is used to validate experimental load-displacement curves which are obtained by testing bonded polymers. This new approach is compared with the four-point bending fracture experiment, and the measured fracture toughnessess of the same bonded materials of two kinds of approaches are shown to be close (15-25% difference).

Compression-after-impact response of woven fiber-reinforced composites

“…The reduced strength and critical energy release rates point to the presence of impact-induced damage beyond the circular delamination zone. In addition, recent investigations [37] based on an efficient short-beam shear approach to measure the mode II fracture toughness of bonded materials and composites indicate that mode-II fracture toughness of undamaged materials is lower than those measured based on previous techniques. Fig.…”

Effect of Tow Size and Interface Interaction on Interfacial Shear Strength Determined by Iosipescu (V-Notch) Testing in Epoxy Resin

“…When considering the SBS, concerns are often raised relating result accuracy. Stress concentrations about the roller supports and mixed-mode bending are both commonly observed to created complex stress distributions that may not provide the most representative conditions of interfacial shear testing [ 17 , 18 , 19 ]. Iosipescu testing removes these concerns by creating a region of pure shear stress across the center of the specimen.…”

An experimental study on the crack initiation from notches connected to interfaces of bonded bi-materials

“…The adhesives were chosen such that their bulk properties were closer to that of the polymer. This was done to ensure that the specimen is modeled as a bi-material with the adhesive interface being modeled as a line without any thickness; but with different bonding strengths and fracture toughness than the bulk polymers or aluminum [11]. The specimens were bonded together using a special fixture under high pressure to achieve minimum adhesive thickness.…”