Investigations were conducted to obtain a valid measure of the compressive strength of filament-wound plastic composites. Working with flat, unidirectional specimens, and commencing with standard methods of evaluation, a series of tests was conducted with variations in procedure and specimen geometry. Resulting compressive strength values were relatively low and, on considering the mode of failure, it was concluded that this property could not be determined by a method in which load is applied directly to the specimen ends.

Consequently a new method was developed in which load is applied to the faces of a specimen through wedge grips. Using this technique and a specimen of a particular geometry, the compressive strength of a unidirectional material with a glass content of 85 weight per cent was determined to be 167,500 psi. Preliminary investigations with wound rings have provided some indication of the validity of this value.