Engineering theories relevant to the failure of materials through fracture and fatigue.

MLO1 Understand complex engineering theories relevant to the failure of materials through fracture and fatigue.

MLO3 Utilise a critical and evaluative approach to solving complex problems.

MLO5 Exercise creativity and initiative in the development of solutions to complex engineering problems.

Assessment Task

Delamination is a common failure mechanism within composite laminates. Delamination occurs when layers of fibre become separated. A technique to improve the delamination properties of composite laminates is z-pinning. Here, carbon fibre or metallic pins are inserted through the thickness of the laminate to improve the mode I fracture resistance (figure 1).

You will be provided with full geometric information (ASTM D5528) and data for double cantilever beam (DCB) tests of both unpinned and pinned carbon fibre/epoxy laminates. Furthermore, you will be provided with tensile test data that captures the z-pin pull-out behaviour. For this assessment, you will create a finite element model that predicts the mode I fracture of unpinned and pinned laminates (figure 2).

Your task has three aspects:

model the mode I fracture of an unpinned composite laminate and compare your predictions to experimental data
incorporate the non-linear behaviour of z-pins into your model and compare with experiment
perform a parametric study of z-pin location and count within the laminate

Sample Solution

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