I assume that by "laminated" you are talking about an automobile windshield. The repair process injects a penetrating adhesive, that both restores optical clarity and helps prevent the chipped area from starting a crack. The process is less successful at stopping the spread of a crack, once begun. My understanding is that this process can only be used on chips and cracks that have not penetrated beyond the laminating film, to the second layer of glass. In most locales here in the USA, if the inner layer has been affected, the windshield has to be replaced.
This process doesn't have much in common with acrylic aircraft windshields. There are solvent adhesives that will thoroughly bond acrylic cracks, but optical clarity will usually be lost. It can also be difficult to assure complete penetration of the adhesive solvent, which makes it hard to assure that full strength has been restored, on installed windows. Here is the text of FAA AC43 that addresses acrylic window repair, in unpressurized aircraft. In the absence of more specific data from the airframe or window manufacturer, AC43 contains "approved data" to document a repair.
These repairs are applicable to plastic windshields, enclosures, and windows in nonpressurized airplanes. For pressurized airplanes, replace or repair plastic elements in accordance with the manufacturer's recommendation. When windshields and side windows made of acrylic plastics are damaged, they are usually replaced unless the damage is minor and a repair would not be in the line of vision. Repairs usually require a great deal of labor. Replacement parts are readily available, so replacement is normally more economical than repair.
a. Minor Repairs.
There are times, however, when a windshield may be cracked and safety is not impaired. In that case, repairs can be made by stop-drilling the ends of the crack with a # 30 drill (1/8 inch) to prevent the concentration of stresses causing the crack to continue. Drill a series of number 40 holes a half-inch from the edge of the crack about a half-inch apart, and lace through these holes with brass safety wire (see figure 3-24) and seal with clear silicone to waterproof.
b. Temporary Repairs.
One way to make a temporary repair is to stop-drill the ends of the crack, and then drill number 27 holes every inch or so in the crack. Use AN515-6 screws and AN365-632 nuts with AN960-6 washers on both sides of the plastic. This will hold the crack together and prevent further breakage until the windshield can be properly repaired or replaced. (See figure 3-24.)
c. Permanent Repairs.
Windshields or side windows with small cracks that affect only the appearance rather than the airworthiness of a sheet, may be repaired by first stop-drilling the ends of the crack with a # 30 or a 1/8-inch drill. Then use a hypodermic syringe and needle to fill the crack with polymerizable cement such as PS-30 or Weld-On 40, and allow capillary action to fill the crack completely. Soak the end of a 1/8-inch acrylic rod in cement to form a cushion and insert it in the stop-drilled hole. Allow the repair to dry for about 30 minutes, and then trim the rod off flush with the sheet.
d. Polishing and Finishing.
Scratches and repair marks, within certain limitations, can be removed from acrylic plastic. No sanding that could adversely affect the plastic's optical properties and distort the pilot's vision should be done on any portion of a
(1) If there are scratches or repair marks in an area that can be sanded, they may be removed by first sanding the area. Use 320- or 400-grit abrasive paper that is wrapped around a felt or rubber pad.
(2) Use circular rubbing motions, light pressure, and a mild liquid soap solution as a lubricant. After the sanding is complete, rinse the surface thoroughly with running water. Then, using a 500-grit paper, continue to sand lightly. Keep moving to higher grit paper and sand and rinse until all of the sanding or repair marks have been removed.
(3) After using the finest abrasive paper, use rubbing compound and buff in a circular motion to remove all traces of the sanding.
----- Original Message -----
From: Jim Campbell
Sent: Monday, May 09, 2005 2:52 AM
Subject: [musketeermail] windshields
In Australia, you can get your laminated windshield repaired with an
acrylic process. You probably can in the US of A too! What I want to
know is - is this a useful process for Aircraft windshields. Or will
it result in weakness?
Anyone tried it?
[Non-text portions of this message have been removed]
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