Increase of shear fracture energy of adhesive joints using double-double laminates

Double – Double (DD) is a new family of laminates that holds the potential to completely overhaul the design of composite structures. These laminates are not only lighter and more robust than the classical QUAD laminates, but they also accelerate manufacturing processes and reduce costs. However, the application of DD laminates as substrates in adhesive joints has not been studied so far. In this work, end-notched flexure (ENF) tests with composite substrates are performed in both QUAD and DD configurations. The main goal is to evaluate the maximum load and shear fracture energy for both laminates. Additionally, the displacement fields are measured through the digital image correlation (DIC) analysis. Experimental results showed that DD laminates can significantly improve the shear fracture energy of adhesive joints and also delay the crack propagation over the test. The findings presented herein could play a crucial role in driving significant alterations in the design procedures of adhesive joints with composite materials, highlighting the DD advantages.