Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA 92093, USA.
Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA 92093, USA.
Mater Sci Eng C Mater Biol Appl. 2014 Feb 1;35:441-8. doi: 10.1016/j.msec.2013.11.024. Epub 2013 Dec 1.
Osteoderms are bony scutes embedded underneath the dermal layers of the skin acting as a protection of the alligator (Archosauria: Crocodylia) internal organs and tissues. Additionally, these scutes function as an aid in temperature regulation. The scutes are inter-linked by fibrous connective tissue. They have properties similar to bone and thus have the necessary toughness to provide protection against predators. The scutes consist of hydroxyapatite and have a porosity of approximately 12%. They have a disc-like morphology with a ridge along the middle of the plate, called the keel; the outer perimeter of the disc has depressions, grooves, and jagged edges which anchor the collagen and act as sutures. Computerized tomography reveals the pattern of elongated pores, which emanate from the keel in a radial pattern. Micro-indentation measurements along the cross-section show a zigzag behavior due to the porosity. Compression results indicate that the axial direction is the strongest (UTS ~67 MPa) and toughest (11 MJ/m(3)); this is the orientation in which they undergo the largest external compression forces from predator teeth. Toughening mechanisms are identified through observation of the damage progression and interpreted in mechanistic terms. They are: flattening of pores, microcrack opening, and microcrack growth and coalescence. Collagen plays an essential role in toughening and plasticity by providing bridges that impede the opening of the cracks and prevent their growth.
骨板是嵌入在鳄鱼（主龙形类：鳄目）皮肤真皮层下的骨质鳞片，起到保护内部器官和组织的作用。此外，这些鳞片还有助于调节体温。鳞片通过纤维结缔组织相互连接。它们具有类似于骨骼的特性，因此具有足够的韧性，可以提供对捕食者的保护。这些鳞片由羟磷灰石组成，具有约 12%的孔隙率。它们具有盘状形态，板的中间有一条脊，称为龙骨；盘的外周边缘有凹陷、凹槽和锯齿状边缘，这些边缘固定胶原蛋白并起到缝合线的作用。计算机断层扫描揭示了长形孔的模式，这些孔从龙骨呈放射状发出。沿着横截面的微压痕测量显示出由于孔隙率而呈之字形的行为。压缩结果表明，轴向方向是最强的（UTS~67MPa）和最坚韧的（11MJ/m3）；这是它们从捕食者的牙齿承受最大外部压缩力的方向。通过观察损伤的进展，确定了增韧机制，并从力学角度进行了解释。它们是：孔隙的扁平化、微裂纹的张开、微裂纹的生长和合并。胶原蛋白通过提供阻碍裂纹张开和防止其生长的桥梁，在增韧和塑性方面发挥着重要作用。
