BS in Materials Engineering
Materials Engineering Department
Twelve different species of cactus spines from 6 different genera were collected from living specimens and maintained in a dry storage environment. Spines from each species underwent 3-point bend testing, XRD testing, and SEM imaging. XRD analysis was used to verify the presence of cellulose whisker like nanocrystals and to calculate the percent crystallinity of each spine. SEM images were captured of fracture surfaces at viewing angles of 90° and 45° relative to the fracture surface, with magnifications ranging between 150x and 4,000x. A total of six spines from each species were tested in three point bending using a high-resolution load cell. The elastic modulus and fracture strength varies between species and between individual spines within a species. The 12 species can be separated into 3 different flexural strength categories. The high, medium, and low strength spine categories demonstrate differences in percent crystallinity and fiber size. The percent crystallinity ranged from 48.0% to 76.3%, with higher crystallinities exhibited in the stronger spines. Every XRD scan exhibited a crystalline peak at 22.7°, confirming the expected presence of cellulose I within the spines. Fiber size within the spines ranged from 2.9 to 10.0 microns, with little in surface texture and spine structure.