Are you interested in evaluating the mechanical damage of tissues or evaluating how collagen damage influences mechanical properties?? Well, then this paper is for you! A new article published in The Journal of the Mechanical Behavior of Biomedical Materials shows that CHPs can help give quantitative information regarding the damage to collagen fibers at a molecular level. The authors explain how this molecular-level damage influences the mechanical properties of the macro-scale cerebral arteries from sheep. In this study, they showed that the CHP staining intensity correlated strongly with the model prediction values. Moreover, CHPs allowed each damage variable to be independently verified.
Abstract: The present experimental-modelling study provides a quantitative interpretation of mechanical data and damage measurements obtained from collagen hybridizing peptide (CHP) techniques on overstretched sheep cerebral arterial tissues. To this aim, a structurally-motivated constitutive model is developed in the framework of continuum damage mechanics. The model includes two internal variables for describing the effects of collagen triple-helical unfolding via interstrand delamination: one governs plastic mechanisms in collagen fibers, leading to a stress softening response of the tissue at the macroscale; the other one describes the loss of fiber structural integrity, leading to tissue final failure. The proposed model is calibrated using the obtained mechanical experimental data, showing excellent fitting capabilities. The predicted evolution of internal variables agree well with independent measurements of molecular-level CHP-based damage data, obtaining an independent a posteriori validation of damage predictions. Moreover, available data on inelastic tissue elongation following supraphysiological loads are successfully reproduced. These outcomes further the hypothesis that the accumulation of interstrand delamination is a primary cause for the evolution of inelastic mechanisms in tissues, and in particular of stress softening up to failure.