Research On The Constitutive Relation And Wave Propagation Of Carbon-phenol With MOC

With the wide application of carbon/phenolic composite in spacecrafts and missile hulls, the prediction of dynamic response or internal damage of structures subject to explosion, impact or the shock wave induced from the sediment of high-energy particle beam and the evaluation of capability of composite in defending stress wave, aroused the study of the constitutive relation and the characteristic of stress wave propagating. The mechanical properties of carbon-phenolic depends on the properties of each phase in it, and is evidently influenced by the manufacturing progress, while micro-mechanics provides the way to calculate the macro-mechanical properties of composites according to the properties and geometries of each phase in it, this method was utilized to study the constitutive relation and the characteristic of stress wave propagating in carbon/phenolic composite in this paper, the main progress follows as:The solidification technique of phenol-formaldehyde resin (PF resin) had been studied, and then the specimens of solidified PF resin were prepared successfully for study on the constitutive relation of solidified PF resin.In the range of strain-rate from 10 to 103 1/s, a series of quasi-static compression experiments and SHPB experiments were performed on the solidified PF resin. In those experiments wave shapers have been utilized to modify the incident wave so that the condition of constant strain rate is satisfied more sufficiently. The effect of outer factors on the stress equilibrium of early stage in the specimen was analyzed, and the methods to improve the uniformity of stress in specimen at early stage were given. The elastic wave velocity of specimens can be determined by the wave shape fitting of the predicted transmitted wave with the measured transmitted wave at the early stage, furthermore, the shifting-time in SHPB data processing can be determined. The experiments show that the solidified phenolic resin is a kind of nonlinear rate-dependent material accompanied with internal damage evolution, and solidified phenolic resin shows character of brittleness at high strain rate and room temperature.A rate-dependent damage evolution modified ZWT nonlinear constitutive ralation is adopted, an object function of least square was established according to the experimental results. The searching space of each decision variable was foreordained with conventional optimizing method, and all parameters in ZWT model for solidified PF resin were determined with Generic Algorithms. The theoretical predictions are in good agreement with the experimental results.Based on the Method of Cell (MOC), the effective elastic properties of resined fiber bundle with parallel or arbitrary orientation was studied, and a micro-mechanical model of resined plain-woven carbon fabric was established with the classical laminate theory, then, the method of calculation of the elastic moduli of resined plain-weave carbon fabric was presented, and can be extended to the whole carbon/phenolic composite.Non-homogenized dynamic method of cell (NHDMOC) is a method of investigatingstress wave propagation in laminated materials, the formula and initial boundary conditions were derived for the numeric simulation of stress wave propagating with NHDMOC under the condition of one dimension strain, the corresponding program was designed and checked. Comparison was made between the results of wave propagating in the linear elastic laminated materials obtained from this program and those from propagation matrix theory, and good agreement is achieved. The calculation of dynamic response under the loading of incident pulses with different rising-time shows that the oscillation of stress wave reflects the macro-heterogeneity of laminated materials, and that the oscillation becomes more distinct as the rising-time becomes steeper. For the periodical laminate, the oscillation period of stress wave depends on the width of each cell and the width of the whole representative cell.At the end of the paper, the NHDMOC was combined wit...