High strain rate response of nanofiber interlayered structural composites

Nanofibrous interlayer toughening strategy for laminated composite materials typically demonstrated at quasi-static loading is here evaluated under high strain rate deformation. Carbon fiber reinforced composite laminates of (0/90)25s stacking sequence are interlayered by polystyrene-co-glycidyl methacrylate (P(St-co-GMA)) nanofibers which are chemically tuned for interfacial compatibility when embedded in epoxy matrix. The cubical composite specimens are cut and subjected to high strain-rate deformation via Split Hopkinson pressure bar testing. Specimens are hit at their through-the-thickness (stacking) and side-to-side (in-plane) directions. The change in the dissipation of energy due to altered interlaminar microstructure is monitored and reported. Enhancement in the capacity of the energy dissipation due to the nanofibrous interlayers is as high as 80% in-plane and 40% through thickness directions, depending on the strain rate. The results overall suggest that interlayer toughening strategy used in this work prevents the formation of critical matrix cracks that can cause the formation of instantaneous mode II delamination. Incorporation of the nanofibers without causing notable weight penalty effectively toug

Loop security and tensile properties of polyblend and traditional suture materials

Tensile and knot properties of new generation (polyblend) and traditional suture materials in orthopedic surgery were investigated in standard laboratory conditions. Study focused on Fiberwire No. 5 and 2, Ethibond No. 5, 2 and 00, Orthocord No. 2, MaxBraid No. 2, Prolene No. 0 and 00, PDS No. 0 and 00, and Vicryl No. 2, 0 and 00. A 27-cm suture loop was fastened with 10 knots for ten samples for each type. Test parameters were tensile load to failure, elongation at failure point and knot slippage, and volume of 10-fold knots. Results were compared using ANOVA test. Failure load of No. 5 Fiberwire (625.0 +/- A 30.0 N) was significantly higher compared to all other suture types. Tensile strengths of MaxBraid No. 2 (287 +/- A 11 N) was significantly stronger compared to two other No. 2 polyblend sutures types and Ethibond No. 5. Knot slippage of Fiberwire No. 5 (14 +/- A 1.9 mm) was significantly higher compared to all other suture types. Ethibond No. 2 (0.1 +/- A 0.3 mm) had the lowest knot slippage. Elongation at the failure point of Fiberwire No. 2 (5%) was significantly lower than all other suture types. Mean calculated knot volume of #5 Fiberwire (73 +/- A 6.9 mm(3)) was significantly higher compared to #5 Ethibond (53 +/- A 4.8 mm(3)). Results of the study proved presence of significant differences between tensile and knot properties of various suture types and sizes. Loop security of larger diameter sutures is not always higher than thinner sutures. Suture elongation and knot slippage are important failure modes for high-diameter sutures and short-suture loops

Vibration characteristics of grafts for the tympanic membrane

Perforation of the tympanic membrane occurs frequently as a result of infection, external trauma, and high-level impulsive sound pressure, such as that associated with an explosion. Many different surgical techniques can be used to repair the tympanic membrane and ossicles. Clinical operations such as tympanoplasty are undertaken to repair the damaged tympanic membrane and ossicles, thus improving hearing and reducing the chance of infection. The membrane is repaired or replaced with the use of graft materials, either from the patient's body or from artificial sources. The selection of graft material is very important because, as much as possible, it must exhibit the same dynamic behavior as the natural membrane. To compare various allograft materials, investigators developed a model of the ear on which different graft materials can be replaced. Three different membrane materials-irradiated allograft dura (Tutoplast (R) Dura; IOP Inc., Costa Mesa, Calif), irradiated allograft fascia lata (Tutoplast Fascia Lata; IOP Inc.), and irradiated allograft fascia temporalis (Tutoplast Fascia Temporalis; IOP Inc.) - were used. Vibration responses of these membrane materials produced by defined sound signals with different frequencies were recorded by a small strain gauge; the spectra of sound for various corresponding input signals were recorded, and the results were compared with those of the sample graft material. Tutoplast Fascia Lata accomplished the best dynamic performance in vitro. Additional clinical and experimental data are needed, however, to determine which of these materials provides the best audiological and clinical performance

Biomechanical analysis of multilevel discectomy and excision of posterior longitudinal ligament: An in vitro study in sheep

Aim: This experimental biomechanical study was performed to determine the effects of multilevel anterior cervical discectomy and excision of posterior longitudinal ligament (PLL) to stabilize the cervical spine using an in vitro animal model. Materials and Methods: Fifty fresh cadaveric C3-C6 sheep spine specimens were divided into five experimental groups: Group A was the control group; Group B, one-level discectomy; Group C, two- level discectomy, Group D, three-level discectomy, and Group E, three-level discectomy and excision of PLL, respectively. The specimens were subjected to non-destructive loads cycled from zero to five Newton-meter for flexion, extension, right and left lateral bending, and axial rotation on an electrohydraulic test machine. Load displacement curves were obtained via collected data using strain gauges. The values were obtained for all five groups, statistical differences were determined respectively (P < 0.05, ANOVA). Results: One- level discectomy was less stable than the control group, two-level discectomy was less stable than one-level discectomy and three-level discectomy was less stable than two-level discectomy, respectively (P < 0.05). Excision of PLL did not seem to affect stability (P > 0.05). Conclusion: Our data suggested that cervical discectomy decreases stability of sheep spine pieces

Effect of antibiotic loading on the shear strength at the stem–cement interface (Shear strength of antibiotic loaded cement)

The purpose of this study was to investigate the effects of addition of antibiotics into cement powder on the shear properties of the cement–metal interface. The approach involved adding 800 mg of teicoplanin to 40 g bone cement powder in the t-800 group, 1,600 mg teicoplanin in the t-1,600 group, and no antibiotic in the control group. Industrially prepared bone cement containing 500 mg of gentamicin was used as group g-500. Each group consisted of ten samples. Cement–metal interfaces were produced using metal discs with porous surfaces (1 μm) and templates at the third minute. Shear stability of specimens was measured in a material testing machine. The ANOVA test was used for comparison between the mean shear results of each group. Results showed that mean shear stress to failure values were 12.28 ± 3.35 MPa for the control group, 11.72 ± 3.09 MPa for the t-800 group, 13.25 ± 2.36 MPa for the t-1,600 group and 13.09 ± 2.58 MPa for the g-500 group. No statistically significant differences were found between results of the groups. Results of the study have proven that addition of 1,600 mg of teicoplanin or 500 mg gentamycin in 40 g of bone cement does not decrease the shear strength at the cement–metal interface significantly on the day of application