A procedure was finally developed for solvent bonding model capsules 

 that produced high-strength bonds over 100% of the joint area (Figure 40): 



(1) assemble the model capsule with 0.005-inch spacers between pentagons, 



(2) place a clamping restraint on it in the form of rubber bands cut from auto 

 inner tubes, (3) introduce solvent into the joint by means of a syringe (results 

 in complete wetting of joint surfaces by capillary action), and (4) rapidly 

 remove the spacers before the joint surfaces are bonded, thus permitting the 

 clamping forces to bring the joint surfaces into intimate contact. This proce- 

 dure was used to assemble and bond model NEMO capsules 1 through 1 1 . 



The annealing of the solvent-bonded model capsules consisted of 

 placing them in an oven heated to 175°F and leaving them there for 24 hours 

 at that temperature. The annealing process, however, did not eliminate com- 

 pletely the residual stresses in the joints introduced into the capsule by the 

 bonding process (Figure 41). Since it was felt that the remaining residual 

 stresses in the model capsule (approximately 1,300-psi shear stress in the 

 joint area) would not significantly decrease the implosion pressure of the 

 capsule, no further effort was made to eliminate the residual stresses after 

 the single annealing operation described. 



Figure 39. Typical air bubbles in an improperly solvent-bonded joint on the 

 15-inch-diameter capsule model. 



66 



