Influence of a tough layer within an orthotropic plate on the mode i stress intensity factor

✍ Scribed by Nava Sela; Leslie Banks-Sills; Ori Ishai

• Publisher: Elsevier Science
• Year: 1989
• Tongue: English
• Weight: 838 KB
• Volume: 32
• Category: Article
• ISSN: 0013-7944
• DOI: 10.1016/0013-7944(89)90187-2

✦ Synopsis

Damage tolerance evaluation of graphite/epoxy composite structures for aircraft applications has recently become a major issue. This is due to experience with propagation of interlaminar flaws which reduce significantly the compressive strength. A "selective toughening" concept, which means introduction of a tough layer within the composite at the most critical locations, is investigated. Stress intensity factors are calculated with finite element analysis by means of displacement extrapolation and Griffith's energy methods in mode I deformation. An orthotropic linear elastic material is analysed and stress intensity factors are calculated for a center cracked plate of this material, with an interlayer of various thickness at the midplane. Results show that the introduction of the interlayer reduces significantly the stress intensity factor in mode I as compared to the homogeneous orthotropic material. However, increase of the interply thickness leads to an increase in the stress intensity factor. Consequently the introduction of a tough layer within the composite is recommended, but as thin as possible.