title: Failure analysis of porcupine quills under axial compression reveals their mechanical response during buckling.
abstract: Porcupine quills are natural structures formed by a thin walled conical shell and an inner foam core. Axial compression tests, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR) were all used to compare the characteristics and mechanical properties of porcupine quills with and without core. The failure mechanisms that occur during buckling were analyzed by scanning electron microscopy (SEM), and it was found that delamination buckling is mostly responsible for the decrease in the measured buckling stress of the quills with regard to predicted theoretical values. Our analysis also confirmed that the foam core works as an energy dissipater improving the mechanical response of an empty cylindrical shell, retarding the onset of buckling as well as producing a step wise decrease in force after buckling, instead of an instantaneous decrease in force typical for specimens without core. Cell collapse and cell densification in the inner foam core were identified as the key mechanisms that allow for energy absorption during buckling.
authors.affiliation: Pontificia Universidad Catolica del Peru, Dept. of Mechanical Engineering, Av. Universitaria 1801, Lima 32, Peru. Electronic address: fgtorres@pucp.edu.pe.
authors.forename: Fernando G
authors.initials: FG
authors.lastname: Torres
authors.affiliation: Pontificia Universidad Catolica del Peru, Dept. of Mechanical Engineering, Av. Universitaria 1801, Lima 32, Peru.
authors.forename: Omar P
authors.initials: OP
authors.lastname: Troncoso
authors.affiliation: Pontificia Universidad Catolica del Peru, Dept. of Mechanical Engineering, Av. Universitaria 1801, Lima 32, Peru.
authors.forename: John
authors.initials: J
authors.lastname: Diaz
authors.affiliation: Pontificia Universidad Catolica del Peru, Dept. of Mechanical Engineering, Av. Universitaria 1801, Lima 32, Peru.
authors.forename: Diego
authors.initials: D
authors.lastname: Arce
mesh_terms: D000825:Animal Structures / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure; D000818:Animals; D001696:Biomechanical Phenomena; D002152:Calorimetry, Differential Scanning; D008422:Materials Testing; D055595:Mechanical Phenomena; D008855:Microscopy, Electron, Scanning; D046328:Porcupines; D011312:Pressure; D017550:Spectroscopy, Fourier Transform Infrared; D013314:Stress, Mechanical
keywords: Buckling; Delamination; Failure mechanism; Porcupine quills