C. Class 2 Repairs
Holes and cracks passing through both skins of a sandwich construction component. The core damage must be able to be covered by a 75 mm (3 inches) diameter circle.
DA 40 Series

Detail Steps/Work Items  Key Items/References 
(1)  Make sure that the area around the damage is clean. 
(2)  Carefully examine the area around the damage. Look specially for disbonding between the inner laminate layers and the foam core.  Do a coin tap test to find the extent of any disbonding or delamination. 
(3)  Remove exterior laminate which is damaged or has become disbonded from the foam core. The edge of the laminate must bond to the foam core.  Refer to Figure 4. 
(4)  Remove the damaged foam core.  Remove sufficient foam core to give a minimum of a 20 mm (0.8 inches) edge around the outside of the damaged area. Refer to Figure 4. 
(5)  Scarf the edges of the external laminate repair area with a grinding disk or block.  Refer to Table 2 for data about the scarf size. 
WARNING: DO NOT GET ACETONE ON YOUR SKIN. ACETONE CAN CAUSE SKIN DISEASE. WARNING: DO NOT BREATHE ACETONE FUMES. ACETONE FUMES CAN CAUSE DISEASE. CAUTION: THERE MUST BE NO GREASE OR DUST ON THE REPAIR AREA. GREASE AND DUST PREVENT A GOOD BOND. 
(6)  Clean the area of the repair.  Use acetone only if any grease or dirt comes to the surface of the repair. 
(7)  Cut and shape a piece of foam core to replace the damaged foam core that you removed in step 4.  Use a sharp knife to cut the foam. 
(8)  Prepare the layers of cloth that you will need to laminate on the inner surface of the foam core.  Refer to the lay-up drawing for the related structure for data about the cloth type and orientation. 

Doc # 6.02.01 Page 219
Rev. 4 09 Jan 2003

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Structures
AMM

DA 40 Series

Detail Steps/Work Items  Key Items/References 
WARNING: DO NOT GET RESIN ON YOUR SKIN. RESIN CAN CAUSE SKIN DISEASE. WARNING: DO NOT GET RESINS, HARDENERS OR SOLVENTS IN YOUR MOUTH OR IN YOUR EYES. THESE CHEMICALS CAN CAUSE DISEASE. 
(9)  Prepare the foam core for inserting in the repair: S Apply a thin coat of resin to the foam core. S Apply a coat of thickened resin to the foam core. S Laminate the inner layers of cloth onto the inner surface of the foam core. Make sure that the fibers in the cloth point in the correct direction.  Refer to Paragraph 6 in this Section. Use one of the 2 methods given in Paragraph 5 of this Section. 
(10)  Apply a thin coat of resin to the area to be repaired. 
(11)  Put the foam core and inner laminate into position in the repair. 
(12)  Pre-cure the repair.  Refer to Paragraph 7 in this Section. 
(13)  Use a sanding disk or block to contour the foam core to the correct shape.  Refer to Figure 4. 
(14)  Clean the repair. 
(15)  Apply a coat of thickened resin to the foam core of the repair. 
(16)  Apply a thin coat of resin to the scarfed edges of the outer laminate of the repair. 
(17)  Repair the outer laminate.  Use one of the 2 methods given in Paragraph 5 of this Section. 
(18)  Pre-cure the repair.  Refer to Paragraph 7 in this Section. 
(19)  Post-cure the repair.  Refer to Paragraph 7 in this Section. 
(20)  When the repair is fully post cured, remove any peel ply and sand smooth the surface of the repair. 

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Structures

Detail Steps/Work Items  Key Items/References 
(21)  Contour the repair so that the final surface level of the repair is slightly lower than the original surrounding area.  Use 150 grit sanding paper. To allow for the paint coat. 
　
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