Favela-Gallegos, C.A.

Soutis, C.

Low cycle fatigue tests (0.5 Hz) in 4-point bending were conducted to study the damage evolution in carbon/epoxy cross-ply laminates. Damage development in the form of matrix (resin) cracking was recorded at different stages of the testing by means of the replica tape technique. The resulting changes in the flexural stiffness are plotted against the amount of damage and number of cycles. Microscopic observation of the replicas revealed matrix cracking at average ply strains of around 0.3% during the first few loading cycles. Matrix cracks are formed from disperse fibre/matrix debonds in the off-axis plies, which eventually coalesce to form a macro-crack. Those matrix cracks were found to grow gradually in size and number in different plies as cycling increased. The effect of matrix cracking initiation and growth on the stiffness of the laminate is found to be less marked than in pure tensile loading, but can still lead to delaminations and ultimately fibre failures. Changes in the flexural stiffness are compared to measured data from reverse bending fatigue tests

Damage evolution under bending fatigue in cross-ply composite laminates

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