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Fm 2009 Patch 9.3.1 Crack: A Complete Guide to Play Without Activation

fatigue crack growth behaviors of cracked plate with bonded composite patch were investigated through experimental and numerical study. experiments involved fatigue tests of 10 mm thick specimens with center crack repaired with unidirectional graphite/epoxy patch. the fatigue crack growth and fatigue life of thick plate were obtained. the stress intensity factor of patched crack was determined from experimental result by comparing the crack growth behavior of specimens with and without repair.

Fm 2009 Patch 9.3.1 Crack

specimens were machined from aluminum sheet (al 7075t6). specimens were 220 mm long 70 mm wide 10 mm thick center cracked tension (cct) specimen as shown in fig. 1. it has a 6 mm diameter hole with 1 mm long crack starter notches on both sides. before the composite patch repair, fatigue loading for precracking was applied until the crack propagated around 1 mm. thus, the initial crack length, 2a, was 10 mm. the cracked specimen was repaired with a graphite/epoxy composite patch. the composite patch was formed in such a way that the crack front was oriented along the width of the patch.

several studies involving both experimental and analytical techniques have investigated the mechanics of bonded composite repairs on cracked thin metallic structures of about 3 mm or less thickness [1], [2], [3], [4]. repairs of thick plates have also been investigated, both numerically and experimentally, but in a limited amount [5], [6]. a few experiments, performed in this area, showed the difference in crack growth rates between the repaired thin and thick components [7]. further, experiments with thick panels have neglected bending effects due to asymmetric repair or attempted to restrict bending by applying stiffeners to the specimens [5], [6]. recently, schubbe and mall [8] investigated the fatigue crack growth rate of thick panels under different patch configuration. they also developed finite element analysis involving three layers of two-dimensional mindlin pate elements to characterize fatigue crack growth behavior of a thick metallic panel repaired with an adhesively bonded composite patch [9]. jones and chiu [10] investigated a series of experimental and numerical studies on the repair of cracks in thick structural components.


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