Failure of woven carbon-polyimide laminates under off-axis compression loading
- Univ. of California, Los Angeles, CA (United States). Dept. of Mechanical and Aerospace Engineering
This paper reports the failure mechanisms in a woven 0/90 carbon-polyimide laminate under 45{degree} off-axis compression loading. The stress carried by the composite increased linearly with increasing levels of applied displacements and, at about 188 MPa, the load dropped suddenly to 172 MPa and remained constant thereafter till about 8.9% strain, at which point the load reduced drastically and resulted in the ultimate failure of the sample. The damage started with the nucleation of several in-plane cracks which split both the wrap and fill yarns completely, and ran diagonally across the sample`s entire width. Upon further loading, the cracking progressed in bundles towards the sample`s interior, and eventually, at a strain of about 5%, a saturation cracking state was reached with each bundle split by at least three-to-four longitudinal cracks. The sample was able to accommodate further strain via nucleation of additional cracks formed at the edges of the longitudinal cracks with their planes parallel to the loading axis and orthogonal to those occupied by the longitudinal cracks. Essentially, these new cracks separated the longitudinally-split bundles in the sample`s thickness direction and resulted in the creation of three-to-four independent bundles from the original well-bonded warp or fill bundle. At this stage, the compressive load carrying capacity of the original bundle was largely compromised and the sample failed through gross delaminations, resulting in the bulging of the sample normal to its largest faces. The above deformation was remarkably different from that observed under bundle-aligned compression loading where the samples failed at an average stress of 588 MPa in more or less brittle catastrophic manner after undergoing only 1.5% strain.
- Sponsoring Organization:
- National Science Foundation, Washington, DC (United States); Department of the Air Force, Washington, DC (United States)
- OSTI ID:
- 616206
- Journal Information:
- Acta Materialia, Vol. 46, Issue 2; Other Information: PBD: 5 Jan 1998
- Country of Publication:
- United States
- Language:
- English
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