A developed process model including the effects of chemical and thermal strains and the cure related elastic material
behavior is established in order to simulate the cure process before cooling stage more realistically. A three-dimensional
finite element method is used to analyze the effect of the curing related parameters on residual stresses in the cure
progress of polymer composites. The obtained results show that the density, the specific heat, the thermal conductivity
and the anisotropic chemical shrinkage have different influences on the final residual stresses before cooling stage.
The effect of elevated temperature on the modulus of glass/epoxy composites was studied. Dynamic mechanic analysis
(DMA) was carried out to investigate the storage modulus, loss modulus, loss factor and glass transition temperature.
Static flexural modulus was also tested by control force mode in DMA. The effect of elevated temperature on the
modulus of the composites was evaluated between 30°C and 120°C. A new temperature-dependent model both for the
dynamic storage modulus and static flexural modulus was proposed. The model only needed one parameter to fit the
experiment data and showed good accordance with experimental results. The physical meaning for the parameter of the
model was given.
Microstructures and mechanical properties of zinc oxide (ZnO) thin films deposited onto glass substrates by rf
magnetron sputtering were studied. Surface morphologies and crystalline structural characteristics were examined using
atomic force microscopy (AFM) and X-ray diffraction (XRD), respectively. Mechanical properties were measured by
nanoindentation. The crystalline structures of ZnO thin films were well ordered with high c-axis (002) orientations. The
surface morphologies of ZnO thin films were smooth and grains grew and distributed uniformly. A single pop-in in the
load-displacement curve was clearly observed at a specific depth (7-10nm) of the thin film. The hardness and Young's
modulus of ZnO thin films were ranged from 8.2 to 10.4GPa and 105 to 120GPa, respectively.
The structural, morphological and optical properties of zinc oxide (ZnO) thin films were investigated. The ZnO thin
films were deposited on glass substrate at room temperature (RT) through radio frequency magnetron sputtering in
different O<sub>2</sub> flux (fixed Ar flux). The structural properties and morphology were studied by X-ray diffraction and atomic
force microscopy, respectively. The highly crystallized ZnO thin films were obtained. It is found that all the films have
preferential orientation in c-axis direction and the crystallinity of the films is strongly affected by O<sub>2</sub> flux. The
crystallinity is improved greatly when the film is annealed in O<sub>2</sub> ambient. Atomic force microscopy results show that the
films are compact and smooth. Near band edge emission peak in photoluminescence spectrum for the typical sample
appears red-shift phenomena. All the films present a high transmittance of above 90% in the visible region.
The residual stresses and mechanisms causing residual stresses in thermoset polymer composites were considered. The
relative importance of the different mechanisms was analyzed. The residual stresses were determined analytically by
viscoelastic model in addition to an experiment. The linear viscoelastic model was used to calculate of residual stresses
in each layer of laminated composites. The fiber Bragg grating (FBG) strain sensor was used to measure the residual
stresses throughout cure. The results are agreed well. The viscoelasticity of composites should be considered during
calculating the residual stresses, and FBG strain sensor is shown to be a reliable for an accurate measurement of the
The strain and temperature sensing performance of FBG are studied in the temperature range of 123K to 273K by the
experiment. The temperature sensitive, strain coefficient and cross-sensitivity coefficient of the sensors are derived
analytically and verified by experiments. It is found that they are nonlinear. Cross sensitivity increase with lower
temperature. At a constant temperature, the Bragg wavelength shift is linear with the longitudinal strain within the range
of 5000 micro strains.
The wind turbine industry is the fastest growing market area for the use of composite materials. Fiber Bragg grating sensor can be used to monitor the mechanical behavior of composite wind blade. The internal strain of composite wind blade during a constant stress amplitude fatigue testing process was monitored with fiber Bragg gratings sensors. FBG sensors can not only be embedded in composite structures to detect fatigue damage, but also have excellent durability compared with other sensors such as electric strain gauges. After 1 million cycles, the FBG sensors can still keep good sensibility. FBGs as a fatigue indicator are a novel sensor to monitor, evaluate and give crash alert for the health state of composite wind blades during their whole service life.