included six specimens of nominal 88.9 88.9-

presence of such cavities was considered unde-

mm- (3.5 3.5-in.-) square cross section and 152.4-

sirable for a systematic study, because it was sus-

pected that their presence would result in extreme

mm- (6-in.-) length. These specimens were desig-

variation in mechanical properties across the

nated PW1 through PW6. The second group

specimen and between samples, and any water

consisted of only three cylindrical specimens of

penetrating into those cavities could degrade the

nominal 91.44-mm (3.6-in.) diam. and 152.4-mm

material subsequent to freezing at subzero tem-

(6-in.) length. These were designated as PWR1

peratures. Subsequently, an RPC material that

through PWR3. The specimens were tested at

resembled wood in texture and was void-free in

room temperature by applying compression load

appearance was selected for the detailed study.

in a screw driven machine at approximately 2.54

The material was supplied by a manufacturer that

mm (0.1 in.) per minute cross-head displacement

was also working with the U.S. Navy on a pilot

rate. Because of the expected large deformation,

program for converting shipboard plastics into

no attempt was made to strain gauge the speci-

RPC (Middleton et al. 1991). Middleton et al.

mens. Instead, displacements corresponding to

described that the manufacturer's innovative pro-

the applied load were recorded manually by dial