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In order to prepare a collagen/PVA composite fiber with collagen hydrolysate, the influence of the molecular weight and ash content of the collagen hydrolysate on the spinning properties and fabrication of the composite fiber should be studied. In this work, collagen with various molecular weights and different ash contents was first blended with PVA for fabrication of different collagen/PVA composite fibers. Next, protein retention rates, titer, tensile strength, elongation at break, and initial modulus of the composite fibers were characterized. Meanwhile, the degree of crystallinity of the composite fiber was measured by X-ray diffraction and the cross-section morphology was observed by a scanning electron microscope. The results show that the cross section of the collagen/PVA composite fiber has a skin-core structure and the collagen hydrolysate mainly distributes on the surface of the composite fiber. A molecular weight of collagen hydrolysate range from 10,000 Da to 100,000 Da is suitable for fabrication; however, if the collagen hydrolysate molecular weight is lower than 10,000 Da, there is obvious protein loss during spinning. In addition, the inorganic salt and ash content in the spinning collagen hydrolysate should be controlled below 1.5%, otherwise there are some holes on the cross section of the collagen/PVA composite fiber and the mechanical properties and crystallinity of the composite fiber are poor. The results of this research would provide a potential choice for applying collagen hydrolysate in textiles and could be a reference for selecting the proper collagen hydrolysate to obtain collagen/PVA composite fiber materials with better performances.

Heat treatment of rigid polyurethane foam (RPUF) was performed at different temperature. The failure degrees of treated RPUF were evaluated by the characterization of tensile properties. The failure process and mechanism of RPUF were further analyzed by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). Experimental results showed that the untreated RPUF maintained the optimal tensile strength and modulus. After the heat treatment at high temperature, the tensile properties of RPUF decreased with the increase of heat-treated temperature due to the gradual degradation of polyurethane matrix. Numerical simulation indicated that the stress concentration in cellular structure model (CSM) constructed according to the Kerner-Rusch relation gradually intensified with the increase of treatment temperature. In addition, the tensile strength and modulus obtained from CSM were agreement with the experimental results. The computation error of CSM was less than 5% in average compared with the experimental data.

The reaction of gelatin with tannic acid using microwave heating with simultaneous cooling (MHSC) in comparison with water bath heating was investigated to get some hints on the non-thermal effect ...

Computational modeling of cardiovascular biomechanics should generally start from a homeostatic state. This is particularly relevant for image-based modeling, where the reference configuration is the loaded in vivo state obtained from imaging. This state includes residual stress of the vascular constituents, as well as anisotropy from the spatially varying orientation of collagen and smooth muscle fibers. Estimation of the residual stress and fiber orientation fields is a formidable challenge in realistic applications. To help address this challenge, we herein develop a growth based Algorithm to recover a residual stress distribution in vascular domains such that the stress state in the loaded configuration is equal to a prescribed homeostatic stress distribution at physiologic pressure. A stress-driven fiber deposition process is included in the framework, which defines the distribution of the fiber alignments in the vascular homeostatic state based on a minimization procedure. Numerical simulations are conducted to test this two-stage homeostasis generation algorithm in both idealized and non-idealized geometries, yielding results that agree favorably with prior numerical and experimental data.

Polyimide (PI) irradiated by pulsed CO2 laser was simulated by finite element method. The finite element model of PI damaged by pulsed CO2 laser was established. We analyzed the temperature and stress characteristics of PI sample under laser irradiation. The effects of laser pulse width and laser spot radius on the damage effect were discussed. The simulation results show that when the stress does not reach the tensile limit,PI will have melt damage,and the body damage is prior to the surface damage. Under the same laser energy irradiation,the thermal stress produced by short pulsed laser is larger than that produced by long pulsed laser,and the effect of thermal stress damage is better. The peak value of stress decreases with the increase of laser spot radius. The larger spot radius is,the worse damage effect is. The occurrence time of peak stress is independent of spot radius.

With the aim at assessment of thermal stabilities of collagen crosslinked with tannic acid under microwave, some thermo-analysis methods have been employed to analyze the properties of the crosslinked product. Meanwhile, for getting some information about the non-thermal effect of microwave on the process, microwave heating with simultaneous cooling (MHSC) method was adopted and compared with water bath heating. The thermal decomposition of the collagen material was characterized by the mass-loss ratio with thermo-gravimetry/derivative thermo-gravimetry curves recorded in nitrogen flow. The crosslinked collagen under MHSC exhibited a higher peak temperature and a lower degree of thermo-oxidative decomposition. The thermal denaturation of the material was determined by the differential scanning calorimetry (DSC) analysis in nitrogen flow. DSC curves showed that microwave gave a higher denaturation temperature and enthalpy, which increased about 3.9 °C and 73.0 J g−1, respectively. The hydrothermal stability of the product was evaluated using the method of micro hot table in glycerol–water condition. The results showed that the shrinkage temperature increased about 3.5 °C under MHSC. In result, microwave gave a higher thermal and hydrothermal stability of the crosslinked collagen, which could be attributed to a stronger bonding of the collagen with tannic acid as a result of microwave non-thermal effect. The results presented here may lay a foundation for the application of microwave in vegetable tanning.

An effective two-step synthesis of high-triplet-energy (ET) bipolar hosts that is simple and broadly applicable is introduced. Electron-donating (D = (9-phenyl-9H-carbazol-3-yl/4-(9H-carbazol-9-yl)phenyl)) and -accepting (A = (tetrafluoropyridin-4-yl/4,6-diphenyl-1,3,5-triazin-2-yl)) units have been coupled to the C9 atom of fluorene to afford the four hosts 3CzFTFP, 9PhFTFP, 3CzFDPhTz, and 9PhFDPhTz with sp3 C9-centered bulky ternary structures, excellent thermal/morphological stabilities, tunable abilities for bipolar charge carrier injection/transport, and identical high ET (2.87 eV). Blue thermally-activated delayed fluorescence (TADF) devices using these new hosts and 2CzPN as the host–guest system exhibited efficient electroluminescence efficiencies of 38 cd A−1/30 lm W−1/17%, which are among the best for 2CzPN-based TADF devices. The generality of this synthetic strategy to high-ET fluorene-coupled D–σ–A type hosts was confirmed by successfully appending other D/A groups ((diphenylamino)phenyl/phenylsulfonyl) to fluorene, affording TPAFBSO.

It has very important application value to investigate the damage mechanism of CaF2 windows irradiated by ultraviolet excimer laser. As significant optical materials, CaF2 windows have been widely used in the ultraviolet photoelectrical field. Because the ultraviolet excimer laser presents favorable characteristics such as short wavelength and high photon energy, the high power excimer lasers are expected to be widely applied in precision laser machining and military field. In this paper, the experiment on damage in CaF2 windows irradiated by 248nm ultraviolet excimer laser was carried out. The damage characteristics of irradiated spots under different experiment conditions were detected by optical microscope. The laser induced damage thresholds of CaF2 windows were calculated by the zero damage probability through linear fitting. The damage mechanism of CaF2 windows were discussed based on the surface characteristics of damage spots. The experimental results indicated that the damage thresholds of zero probability for the 248nm excimer laser to CaF2 windows were 5.6J/cm2 of the incident surface, and 1.1J/cm2 of the exit surface respectively. When CaF2 windows was irradiated by 248nm excimer laser, its damage first occurred to its exit surface, the damage threshold of exit surface was smaller than that of incident surface. As the laser fluence increased gradually, the damage of exit surface was shown to grow exponential and its degree was significantly higher than that of incident surface. This work is helpful to further improve damage resistance of CaF2 windows in high power laser facility. It can provide the necessary references for selection of ultraviolet optical materials and optimization of application.

The mechanical failure behaviors prediction model of rigid polyurethane foam (RPUF) treated under complex thermal-vibration conditions was constructed by experiment of tensile properties and numerical simulation for the further analysis of the failure progress and mechanism of RPUF. On the basis of scanning electron microscope (SEM) observation, a realistic representative volume element (RVE) of RPUF was firstly established by means of Voronoi-spherical tessellations. Tensile properties of RPUF treated under different thermal-vibration conditions were measured subsequently. Results of the tensile properties characterization of RPUF suggested that the thermal and vibration treatment on RPUF reduced its tensile strength and fracture elongation decrease due to the chemical degradation of polyurethane (PU) matrix and physical breaking of the foam structure. The tensile constitutive relationship derived from the tensile experiments was assigned to the realistic RVE, and the thermal-vibration failure prediction model of RPUF was further constructed in the ABAQUS software. The numerical simulation results revealed that the stress concentrations appeared and extended along with the weakness regions of RPUF structure under the external load. The stress-strain curves of thermal-vibration treated RPUF obtained from the prediction model were in well agreement with the experimental results, and the average computation error was less than 3%. It indicated that the prediction model can accurately describe the failure progress of thermal-vibration treated RPUF. This work provides ideas for the design of the foam materials with high thermal-vibration aging resistance by numerical simulation in the future.

In this paper, the PI damage caused by pulsed CO2 laser was simulated. The theoretical model of PI damaged by pulsed CO2 laser was established. The temperature and stress distribution in PI samples were numerically analyzed by finite element method. The simulation results show that under the condition of low incident laser energy, serious melting damage has occurred on the PI surface, and there exists thermal stress damage. The damage of PI by pulsed CO2 laser is mainly thermal damage, and the melting phenomenon will be obvious.

We reported on laser performance of a kW-level 20/400 Yb-doped aluminosilicate fiber. Laser running of ~120 minutes at 1.2kW showed power degradation of ~10.6% and slope efficiency degradation of ~116%, directly justifying serious photodarkening effect.

Fiber-reinforced epoxy sandwich composites, which were designed as the bonded repair patches to better recover the mechanical performance of a central cracked aluminum alloy plate, were layered by carbon and aramid fiber layers jointly and cured by microwave method in this study. The static tensile and bending properties of both carbon-aramid fiber/epoxy sandwich composite patches and the cracked aluminum alloy plates after bonded repair were systematically investigated. By comparing the mechanical performance with traditional single carbon-fiber-reinforced composite patches, it can be found that the bending performance of carbon-aramid fiber sandwich composite patches was effectively improved after incorporation of flexible aramid fiber layers into the carbon fiber layers, but the tensile strength of sandwich composite patches was weakened to some extent. Especially, the sandwich patches with 3 fiber layers exhibited better tensile and bending performance in comparison to patches of 5 and 7 fiber layers. The optimized 3-layer carbon-aramid fiber sandwich patch repaired plate recovered 86% and 190% of the tensile and bending performance in comparison to the uncracked ones, respectively, showing a considerable repair majorization effect for the cracked aluminum alloy plate.