Systematic head injury research in the laboratory requires a reproducible head form, made from engineering materials, that can be instrumented and tested. The mechanical properties of cranial bone are essential to such an effort so that equivalent engineering materials can be selected for the head form. This paper is concerned with the determination of these properties. Conventional materials testing machines were used to obtain the stress-strain relation for the compact layers of human cranial bone in tension. Strain gages applied to each specimen were used to measure strain. One hundred and thirty-nine specimens from thirty subjects were tested in this study, which included parietal, temporal and frontal bone. Data were collected at strain rates ranging from 0.0003 to 150 sec^-1.

The results are presented in the form of stress-strain diagrams to compare the response of several specimens from one subject. These results show that there is no detectable variation in the properties for the regions of bone considered. They also revealed that the modulus of elasticity is rate sensitive. Data from all subjects are used to show that the breaking stress and breaking strain are also rate sensitive. The energy absorbed to failure differed from these properties in that it was not rate sensitive. Statistical analysis of the data revealed no significant differences in the modulus of elasticity, the breaking stress, the breaking strain or the energy absorbed to failure when compared according to type of bone, side of body or age of individual. Several other properties of cranial bone are discussed.

Methods for selecting an appropriate material for a frangible head form are presented. Based on the above results several engineering materials currently available are outstanding candidate materials.