Abstract
There is a global need to design low weight structures for strategic, business, and social purposes.
Reducing weight is critical for improving energy consumption as well as addressing range,
performance, size, and cost challenges associated with structural design, especially in the
automotive and aerospace industries. In recognition of this need, advances are being made in
replacing high strength steels, magnesium and aluminum alloys with carbon fiber reinforced epoxy
composites. These have many merits which include weight reduction for lower fuel consumption,
resistance to environmental degradation and better aesthetic appeal. For most applications, the
carbon fiber reinforced epoxy composites are exposed to cyclic loading leading to fatigue failure.
High cycle fatigue in metals usually evolves by the single crack initiation which propagates until
catastrophic failure. In contrast to metals, damage development in carbon fiber reinforced epoxy
composites occurs in a complex global fashion which occupies an under-researched field. To
enable better design, there is a need for a better understanding of carbon fiber reinforced epoxy
composites, in particular, damage progression during cyclic loading. The aim of this paper is to
investigate damage development during fatigue loading in carbon fiber reinforced epoxy
composites. To this end, carbon fiber/epoxy composites produced from a bi-axial carbon material
with a fiber volume fraction of 30% were investigated. The specimens were prepared using a hand
layup molding technique. The results showed the first two of the three common stages observed
during fatigue damage development. The first stage involved rapid damage, followed by stage two
which is gradual, and the final stage which is rapid was not observed. The obtained results clearly
show the fatigue damage mechanisms in carbon fiber reinforced epoxy composite materials.