Abstract:The comprehensive messages of six types of pattern signals such as broadband waveforms,AE parameters,analog parameters were collected with linear location simultaneously.Features of signals were analyzed for wave form,AE parameters,FFT spectrum and wavelet transform,in which 1300 samples were selected.The dimensional reduction of feature space was brought out by algorithm of multi-resolution wavelet transform,in which 5 features were extracted from each sample.An intelligent pattern classifier with B-P neural network was used in studying the learnt effect of network and the recognition ability for unknown flaw.Experiments showed that the results of recognition were satisfactory when the wavelet spectrum was taken as a sample feature vector.The average recognition accuracy of the six types of flaws was about 90.4%,and the best recognition accuracy amounted to 97.2%.The method has been applied to describing the entire three-point flexural failure process successfully for 90° and 0° specimens with no notch and 0° notched specimens.

Abstract:A method using Computer Tomography(CT) is introduced in the paper,to measure in three dimensions the physical density and porosity of composite materials.A software compatible with PC computer was developed to rebuild images in three dimensions for analyzing and measuring.It is indicated that CT method has a good resolution for composite inner defects inspect and can provide a clear density distribution by rebuilding of images.CT is considered one of the most accurate and effective NDT for composites.

Abstract:Tensile and compressive properties of F-12 aramid fiber and carbon fiber hybrid composites are presented in this paper.Results show that the tensile strength is lower than predicted by mixture rule and present negative hybrid effect,while compressive strength present positive hybrid effect which is lower than the negative hybrid effect of tensile strength.Failure modes of hybrid composite tension and compression differ with non-hybrid composite.

Abstract:Pyrolytic conversion of polycarbosilane(PCS) into ceramic materials can be significantly influenced by active filler(Ti) dispersoids.During pyrolytic decomposition of the PCS matrix,Ti can accelerate PCS pyrolysis and increase ceramic yields of PCS.The linear shrinkage of the preceramic polymers in pyrolyzing and porosity of ceramic products will decrease with the addition of Ti powders,and properties of the ceramic materials can be improved as a result.

Abstract:Development of researches on the deformation behavior and mechanism of discontinuous reinforced metal matrix composite was presented,including elastic deformation,micro-plastic deformation,macro-plastic deformation.In fluence factors on the deformation behaviors of the composites were also discussed,and further studies in the field is propected.

Abstract:Carbon fiber and silicon carbide fiber have been widely used in stealth technology,which are two main kinds of fibers to reinforce radar absorbing materials.Preparatibn methods and microwave permittivity and permeability of radar absorbing carbon fiber and silicon carbide fiber are discussed.Carbon fiber with good radar absorbing can be prepiared by decreasing its heat treatment temperature,changing its cross section shape and size,modifying outer surface and doping other elements into the carbon fiber.Silicon carbide fiber with radar absorbing can be prepared by increasing the heat treatment temperature,modifying fiber surface and doping other elements into fiber.

Abstract:Applications and its prospects of nanometer materials to solid rocket motors are introduced in this paper.Recent technology development and potential applications of nanometer materials on structural and outer protective materials for solid rocket motor cases,ablative materials for nozzles and solid propellant are discussed in detail.

Abstract:In this study,2618 aluminum alloy manufactured by spray process was heated in a heating furnace,and the microstructures were investigated.By the process of heating in a heating furnace and then squeeze-forming,one component of the motorcycle was produced successfully with the semi-solid aluminum alloy.

Abstract:On the basis of analysis and overview of the defects or damage types,repair methods,required equipment and materials as well as its processing for typical honeycomb sandwich structures,more emphases are given on the studies of filling repair process in this paper.It is shown that suitable repair material such as G7A-20 can be with a good operation and can be cured at RT,with a density of no more than 0.8 g/cm3 and tensile strength of more than 3.4 MPa,and as a result more than 80% of design allowable values of compress strength and modulus can be obtained.

Abstract:In this paper,the reason for interlaminar crack between carbon fiber reinforced phenolic resin and high silica reinforced phenolic resin materials is discussed.Results of experiments show that residual stress and influence of buffer layer are the main factors resulting in this problem.By taking measures such as decreasing curing temperature,slowing down heating rate and reducing thickness of the buffer layer etc.,the problem of interlaminar decementafion can be resolved successfully.

Abstract:SiO2 fibre reinforced SiO2 matrix composites were prepared by vacuum hot-pressing at different temperatures holding time,and their microstructure and mechanical properties were then investigated.It was concluded that flexural strength and fracture toughness of the composites were greatly improved compared with that fused SiO2 but tended to decrease with increasing holding time and sintering temperature.This could be principally attributed to the impairation of SiO2 fibres due to their crystallization.

Abstract:High mechanical properties and anti-oxidation stability of SiC matrix composites are dependent on high performance of CVI-SiC matrix materials.Microstructure and composition of the CVI-SiC matrix materials deposited under different CVI conditions are examined by SEM and XRD.Test results show that crystal orientation of the CVI SiC materials is much dependent on reaction temperature.When it is below 1100℃ the CVI SiC materials have single crystal orientation plane(111),and double crystal orientation planes (111,220) with a small amount of orientation plane(311) when the reaction temperature is above 1100°C.The different stacking modes of SiC crystal grain directly influence the properties of the CVI SiC materials and its composites.Moreover,the properties of the CVI-SiC matrix and composites are influenced by reagent flow.In this work,the effects of the depositing temperature and reagent flow on the properties of the SiC matrix are investigated,and the optimized process is introduced.