PHYSICAL PROPERTIES OF EGGSHELLS: A COMPARISON OF THE PUNCTURE AND COMPRESSION TESTS FOR ESTIMATING SHELL STRENGTH

Abstract

Quasi-static compression and puncture methods of measuring eggshell strength were compared by testing consecutive eggs from each of 89 birds alternately until eight eggs per bird were tested by each method. Results indicated that the tensile and shear fracture properties of the shell material were linearly related to each other, and to shell thickness and specific gravity. Both puncture force and compression fracture force were significantly different on a between-hen basis even when adjusted for shell thickness. Puncture force was more closely related to shell thickness on a between-egg basis than was compression fracture force. Puncture force was not related to shell thickness on a within-egg basis. The increase in accuracy gained from repeated puncture measurements on a within-egg basis was discussed.