4. Shear strength 



5. Compressive deformation under load 



If the average value of two test specimens for any of the above-mentioned 

 tests was less than specified in Table 1 , the acrylic sheet from which the 

 specimens were cut was rejected. Upon examination of the test data, only 

 one sheet out of 38 had to be rejected. The mechanical properties deter- 

 mined for all the 38 sheets of 2.5-inch-thick acrylic plastic are shown in 

 Table F-1. 



After the tests the accepted acrylic plastic sheets were officially 

 released for band-sawing into 46-inch-diameter discs. 



Dimensional Tolerance Measurement 



After all the discs had been cut from the accepted sheets, the thickness 

 of each disc at seven different points was measured (Figure F-1). If the thick- 

 ness of the disc was within 2.375<t< 2.625 inches, it was considered to be 

 acceptable, and the given disc was released for thermoforming into sectors. 

 None of the discs were rejected, as all discs met the specified tolerances on 

 thickness (Table F-2). 



After forming the disc into spherical sector by means of heat and 

 application of vacuum in a female mold, the thickness was checked again at 

 six locations (Figure F-1 ). If the thickness was found to be within 

 2.31 5< t< 2.685 inches, the formed sector was considered to be acceptable, 

 and it was released for machining into a pentagon (Table F-2). 



After the pentagons were machined and annealed, they were checked 

 for sphericity and adherence to tolerances specified for the size of the penta- 

 gon. None of the finished pentagons were found to exceed the 32.875< R 

 < 33. 1 25-inch tolerance on sphericity measured at six places (Figure F-1 ) 

 across the outside surface of the pentagon (Table F-2). All but five pentagons 

 met the dimensional tolerance of 37.380< K < 38.020 inches on size measured 

 between nonadjacent tips of the pentagon. The five pentagons, whose K 

 dimension was, in some cases, 0.100-inch less than specified, were also accepted 

 but on the condition that commensurately thicker spacers would be 

 utilized by the contractor in the assembly of the capsule to compensate tor 

 some of the undersize pentagons. The capsule in which the undersized 

 pentagons were used was capsule 3 not slated for manned service but 

 structural testing. The diameter of the penetrations in the polar pentagons 

 was checked at this time also. All of the penetrations were found to conform 

 to the 22.568<d< 22.578-inch dimensional tolerance. 



204 



