Characterisation of Mixed-Mode I-II-III Delamination in Composite Laminates

Owing to low interlaminar strength, delamination is a commonly observed in composite structures. Due to complex loadings in real life applications, delamination is usually occurred in mixed-mode. This chapter begins with the review of the mixed-mode I-II-III delamination characterisation methods. The shear-torsion-bending, pre-stressed beam and bending plate tests are extensively discussed, which include the test setup configuration, advantages and drawbacks of each method. The interactions between different modes on the fracture toughness distribution are also plotted and compared. Subsequently, a new method is proposed to characterise mixed-mode I-II-III delamination. This ten-point bending plate test (10PBP) test induces mode I, II and III concurrently through the bending of the specimen about different axes. This test is successfully implemented on a carbon/epoxy composite. Crack growth is observed along the mid-plane of the specimen where a Teflon is placed. Finite element modelling is required in the future work to quantify the participation of each mode and analyse the delamination behaviour.