Determination of In-Plane Shear Properties of Laminate with V-Notch Rail Shear Test and Digital Image Correlation

Abstract

This article presents the results of the application of Digital Image Correlation (DIC) to measurements of in-plane shear modulus and strength of three different carbon fiber reinforced laminates. Three different approaches to shear strain calculations via DIC are evaluated and compared with standard strain gage measurements. Calculation of shear strain based on averaging DIC strain values of strain gages area in most cases yielded results closest to strain gages, while measurements based on single point strain measuring differed the most from strain gages. These results are attributed to shear strain distribution in the center area of the specimen. Thermoplastic matrix fabric reinforced composite had the lowest shear strength at 5% of shear strain, but the highest ultimate shear strength and strain at failure. Of thermosetting materials, laminate reinforced with unidirectional carbon fiber had shear modulus about 10% lower, than fabric reinforced laminate, but higher ultimate strength and strain at failure. This behavior is attributed to the presence of weaves in fabric reinforcing the laminate, causing shear stiffening of the material, but lowering its ability to deform under shear loading.

Review of material test standardization status for the material qualification of laminated thermosetting composite structures

“…100 Furthermore, the failure analysis can be subsequently carried out to understand the failure phenomena of test specimens, and to possibly verify numerical material models. 101 Karny 102 has reported the application of DIC method to ASTM D7078 in-plane shear specimens with three different types of carbon fiber laminated composites, such as woven fabric carbon fiber poly-ether-ether-ketone thermoplastics and unidirectional and woven fabric carbon fiber epoxy composites. In this experimental work, the shear modulus ( G 12 ) measured by a DIC technique was similar to the value of modulus determined by a strain gage, by resulting in 4.77% difference between two strain measurement techniques.…”