MIL-P-25690B

Abstract

This specification covers the requirements for two classes of transparent monolithic, modified, methyl methacrylate flat stretched sheets that may be formed into parts having superior crack propagation and craze resistance as a result of proper hot stretching (see <a>6.4.2</a>). <b><u>Intended Use:</u></b> The material covered by this specification is intended for use primarily in aircraft glazing applications where superior crack propagation resistance (shatter resistance, craze resistance, fatigue resistance) is required in addition to normal optical, mechanical strength, and heat resistance properties. It is the intent of this specification to ensure, by flat stretching the material, that adequate crack propagation resistance has been introduced into the material and that it has been retained to a satisfactory degree throughout the process. Agencies purchasing sheets or panels of the material for specific purposes may specify additional requirements or provide for those contained herein to be more rigid, or both, as required. If material conforming to this specification is used in applications requiring specialized optical properties, more rigid optical requirements may be specified in the detailed product specification/drawing. In that event, the more rigid requirements of the detailed specification must take precedence. Reference to this specification may be made on drawings or in product specifications in order to indicate that the part in question should be prepared in such manner and from such "as-cast" materials as to possess in its final form the properties required by this specification. Many physical properties of this material vary with temperature/humidity. This fact should be considered by designers, engineers, draftsmen, and prospective users of the material. <br>