(c)
The routed radius can be checked for crazing without having to remove the pane; it can be checked from the inside. If examination of the windowpanes is done on a sampling basis, some windows will have crazed routed radii and will not get checked. However, stretched acrylic has the quality of restraining craze propagation and will probably last until the next overhaul. If crazing is evident in the routed radius above the limits mentioned in par. (d), that pane should be replaced and remaining windows examined.
H30535
500 Joint of Acrylic Pane with Window Frame Forging
Jun 20/87 Figure 602 56-31-0
Page 603
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
(d) Crazing around the routed radius and routed edge may be more or less continuous in which case the maximum depth of penetration shall be 0.012 inch. Crazing around delaminated areas shall not exceed 0.005 inch deep.
D. Delamination (Outer Panes Only)
(1)
The stretching process used in the acrylic pane manufacture results in a lower shear strength parallel to the pane surface than that perpendicular to the surface. Because of this the acrylic behaves, in many ways, like a multilayer laminate. Delamination is a separation of adjacent layers parallel to the pane surface. It can be induced by a blow with a sharp instrument on the pane edge and usually accompanies deep penetrations into the pane surface. For clarity, fine continuous delamination is defined as crazing.
CAUTION: NO DELAMINATION IS ALLOWED IN THE CENTER PANE.
(2)
Outer pane delamination at the extreme edge (Fig. 602) is permissible within the following limits:
(a)
Maximum extension in from edge 0.20 inch
(b)
Maximum length at edge 0.50 inch
(c)
Minimum distance between defects 1.00 inch
(d)
Maximum number per pane 2
(3)
Large delaminations in the routed radius are definitely more serious than crazing at the same place. This is because the stretching process of manufacture decreases the ability of the acrylic to resist spreading of delamination, parallel to the direction of stretching.
(4)
A routed radius delamination will probably not occur as often as a crazing defect in the same place. Whereas the rubber peripheral seal on the outer pane tended to aggravate the crazing, it now serves as a protective bumper against sharp blows on the radius producing delaminations. Should evidence of routed radius delamination be found, the window frame forging should be examined for sharp protrusions and the general fit of the pane in the forging examined.
(5)
Delaminations around the routed edge and routed radius may be continuous and the maximum depth of penetration shall be 0.012 inch. For localized delaminations in the routed radius and routed edge, one local area per side of window pane may have a maximum depth of penetration of 0.025 inch with a maximum length of 0.25 inch provided the crazing around the delaminated area does not exceed 0.005 inch deep.
(6)
Deleted.
(7)
Delamination of the outer pane, at any place other than the edges, is often accompanied by chipping especially in the case of a blow with a blunt object. In the case of penetration by a sharp object the delamination takes the form of a circle concentric with the hole. Delamination and chips are permissible within the following limits:
(a)
Maximum chip depth 0.025 inch
(b)
Maximum size of delamination 0.25 inch diameter
(c)
Minimum distance between defects Twice maximum damage diameter
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56-31-0 Page 604 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Oct 20/87
E. Scratches
(1)
Scratches in the routed radius can have the same criteria applied as for crazing at the same place, except in the case of very severe scratches.
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