| Autor: |
John D. Camping, Ran Y. Kim, Vernon T. Bechel, Mark B Fredin, Steven L Donaldson |
| Rok vydání: |
2003 |
| Předmět: |
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| Zdroj: |
Composites Part A: Applied Science and Manufacturing. 34:663-672 |
| ISSN: |
1359-835X |
| Popis: |
An apparatus was developed to thermally cycle coupon-sized mechanical test specimens to −196 °C. Using this device, IM7/5250-4 carbon/bismaleimide cross-ply ([0/90]2S and [90/0/90/0/90/0/90/0/90]) and quasi-isotropic ([0/45/−45/90]S) laminates were submerged in liquid nitrogen (LN2) and returned to room temperature 400 times. Ply-by-ply micro-crack density (transverse cracks), micro-crack span, laminate modulus, and laminate strength were measured as a function of thermal cycles. The composite micro-cracked extensively in the surface plies followed by sparse micro-cracking of the inner plies. The tensile strength of the two blocked lay-ups (lay-ups with adjacent plies of the same orientation) decreased by 8.5% after 400 cycles. Sectioning of the samples revealed that the micro-cracks in the surface plies spanned the full width of the sample while many of the micro-cracks observed on the edge of the inner plies did not extend to the center of the samples, implying that a rectangular specimen with exposed free edges may result in a significantly different micro-crack density than a sample without free edges. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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Full Text from ScienceDirect