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Mechanically robust and biomimicking scaffolds are needed for structural engineering of tissues such as the intervertebral disc, which are prone to failure and incapable of natural healing. Here, the formation of thick, randomly aligned polycaprolactone electrospun fibre structures infiltrated with alginate is reported. The composites are characterised using both indentation and tensile testing and demonstrate substantially different tensile and compressive moduli. The composites are mechanically robust and exhibit large strains-to-failure, exhibiting toughening mechanisms observed in other composite material systems. The method presented here provides a way to create large-scale biomimetic scaffolds that more closely mimic the composite structure of natural tissue, with tuneable tensile and compressive properties via the fibre and matrix phases, respectively.

A viscous-elastic-plastic indentation model was used to assess the local variability of properties in healing porcine bone. Constant loading- and unloading-rate depth-sensing indentation tests were performed and properties were computed from nonlinear curve-fits of the unloading displacement-time data. Three properties were obtained from the fit: modulus (the coefficient of an elastic reversible process), hardness (the coefficient of a nonreversible, time-independent process) and viscosity (the coefficient of a nonreversible, time-dependent process). The region adjacent to the dental implant interface demonstrated a slightly depressed elastic modulus along with an increase in local time-dependence (smaller viscosity); there was no clear trend in bone hardness with respect to the implant interface. Values of the elastic modulus and calculated contact hardness were comparable to those obtained in studies utilizing traditional elastic-plastic analysis techniques. The current approach to indentation data analysis shows promise for materials with time-dependent indentation responses.

Mechanical integrity of the chorioamnion membrane, and the component chorion and amnion layers, was assessed with biaxial puncture testing. Fetal membranes were obtained from term placentas following labored natural delivery or scheduled cesarean section. Preterm specimens were obtained from deliveries prior to 37 weeks gestation. Dividing and peripheral membranes were obtained from multiple gestation pregnancies. Specimens were gripped between parallel plates with circular openings and loaded with an instrumented, hand-held blunt probe until rupture occurred. Peak force was recorded and rupture sites were examined. Defects in multi-layered membranes differed in both size and shape in the individual layers. Compared with chorion and whole chorioamnion, amnion was more mechanically sensitive to different obstetrical conditions. Amnion varied in response at different physical locations within the same patient. Membrane and component puncture force data were used to calculate biaxial failure strength. Membrane stresses arising from amniotic fluid pressure were computed as a function of gestational age, and compared to membrane strength to examine the criterion for membrane failure in vivo. Possible mechanical conditions for preterm membrane rupture were examined.

The mechanical behavior of human amnion is examined under uniaxial tensile loading conditions. Monotonic strain-to-failure and stress-relaxation tests are described for membrane strip samples of amnion obtained by removing the chorion cell layer from specimens of whole chorioamnion. The monotonic behavior of the amnion is characterized by a large stress-free strain (approximately 10%) prior to a quadratic load-displacement response. Substantial stress relaxation behavior (ranging from 20-80%) is observed, described by a two time-constant exponential decay. The effects of the application of a topical antiseptic and of prior straining and relaxation on subsequent monotonic failure properties are examined. The results suggest that while amnion is a remarkably resilient tissue material, its mechanical behavior is typical of nonlinear viscoelastic materials, and depends strongly on its history.