FABRICATION 



The procedures for fabrication of capsules 1 , 2, and 3 were the same 

 as for the prototype capsule described in the main body of the report except 

 that a different adhesive and acrylic plastic joint spacers were used in capsules 

 2 and 3. These acrylic joint spacers were not removed prior to setting of 

 adhesive, resulting in considerable labor saving. No changes in tooling were 

 made prior to fabricating capsules 1 , 2, and 3 except for changing the curva- 

 ture of the mold from nominal 33.1 87 to actual 33.000 inches and giving the 

 newly machined surface a 16-rms finish. 



The adhesive selected for capsules 2 and 3 was Swedlow's SS-621 7, 

 which has a polymerization rate that can be controlled more accurately 

 during bonding of the joints. Prior to substituting SS-621 7 adhesive for 

 PS-18 adhesive, it was evaluated for strength and immunity to seawater. 

 Both its strength and resistance to seawater (6,360-psi average tensile 

 strength prior to immersion and 5,990 psi after 42 days' immersion) were 

 found to be equivalent to that of PS-18. In addition, the cured adhesive 

 was not only transparent but colorless, rather than yellow as PS-18 generally 

 is. 



QUALITY CONTROL 



Very stringent quality controls were maintained during every step 

 of the fabrication to insure that the completed capsules would perform 

 structurally as well, or better than, the prototype capsule described in the 

 main body of the report. Five different quality controls were applied, and 

 the results were recorded by inspectors. 



Material Properties 



Each sheet of 48 x 60 x 2.5-inch acrylic plastic was accompanied by 

 an invoice from the manufacturer stating the type of material, date cast, 

 and batch number. Upon receipt of the material, a 1 2 x 48 x 2.5-inch strip 

 was cut from each sheet. From this strip a total of 10 (two for each test) 

 specimens were machined and subsequently tested to determine the following 

 material properties: 



1 . Compressive strength and compressive modulus of elasticity 



2. Tensile strength and tensile modulus of elasticity 



3. Flexural strength and f lexural modulus of elasticity 



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