The experimental and numerical studies on far-field pyroshock responses of composite panels are presented in this paper. The purpose of this study is to find out the region of composite panel where the pyroshock response is high and thereby the panel can be used as a testing bed to examine tiny elements such as electronic parts used in spacecraft. Experiments based on bi-plate technology are conducted on different combination of e-glass/epoxy composite panel parameters. The structural responses are analyzed using panel parameters as well as shock response spectrums (SRSs) computed from the acceleration-time histories. The experiments are carried out for a low range of chamber pressure with projectiles of varying length to get the far-field response of the test panel. The accelerations of the panel at selected locations are measured by the PCB Piezotronics (Depew, NY) accelerometers and National Instruments-Data Acquisition (NI-DAQ) system (National Instruments, Austin, TX) with labview software. Finite element analysis (FEA) for the pyroshock environment is done using abaqus/Explicit software. Due to the symmetry of the structure as well as the loading, only quarter portion of the panel is analyzed. From the results, it is found that acceleration increases as thickness of composite test panel increases (about 20–70%) for all the combinations of projectile length and chamber pressure at all the points considered on the laminate. Transfer of acceleration from steel plate onto composite panel through physical connections is predominant (about 90–95% of total transfer) than that through air media between the steel plate and the composite panel. Velocity with lower momentum induces lower frequency modes to be dominant whereas velocity with higher momentum induces higher frequency modes. Normally higher accelerations (about 40–90%) are experienced at the center location than any other locations under consideration. The SRSs are obtained both from FEA and experiments. The experimental study shows good agreement with the FEA results both in acceleration time history as well as in SRS.

The relaxation by creep recovery of plasticized poly lvinyl chloride) (PVC) was tested in relation t o applied stress

The effect of different fiber orientations of composite panels of E-Glass/Epoxy under far-field pyroshock is presented in this article. To get the far-field pyroshock response, the experiments are conducted using Biplate technology under low range of input chamber pressures to projectiles of three different lengths. PCB accelerometers and NI-DAQ system with LabView software are used to capture the structural responses in the form of acceleration-time histories and analyze them at selected locations. Abaqus/Explicit code is used in the Finite Element Analysis (FEA) for the pyroshock response of composite panels with different fiber orientations. From the results, it is found that the selected locations on the [0/90/645] s WRM (Woven Roving Mat) laminate experience higher accelerations, above 30% extra, than other fiber orientations. Since [0/90/645] s laminate has lengthier fiber rovings along the diagonal direction, higher Young's modulus along the fiber direction and the most vibration modes are diagonally biased, the response amplitude would be high enough to experience maximum acceleration. The acceleration responses are obtained both from FEA and experiments and show good agreement. POLYM.

The experimental study on far-field pyroshock responses of carbon/glass/ Kevlar-epoxy composite panels are presented in this article. Bi-Plate Technology is used to conduct all the experiments on different combination of carbon, E-glass, and Kevlar composite panel parameters, with epoxy resin as matrix. The structural responses computed from the acceleration-time histories are analyzed. Low range of chamber pressure and projectiles of three different lengths are used to carry out the experiments so that the farfield response of the test panel is ensured. PCB accelerometers and NI-DAQ system are used to capture the accelerations of panel at selected locations. Among all the composite panels, the one which is of Kevlar-epoxy laminate shows the least acceleration because the said material has high vibrational energy absorption rate. The glass-epoxy laminate being higher mass rate shows the intermediate category and the carbon-epoxy accelerates itself the most. Hence, these types of fibers may be utilized in appropriate areas according to their degree of acceleration to minimize the effect of the farfield pyroshock response.

SynopsisThe temperature dependence of tensile creep of plasticized poly(viny1 chloride) (PVC) was tested under differently applied stresses. The steady creep rate showed two distinct stages, depending on stress and temperature. At relatively low stresses the activation energy (0.2 eV) which characterized the steady creep mechanism of stage I, showed no stress sensitivity. Under high stresses (stage 11) the energy-activating steady creep was of the order of 1 eV and increased excessively with increasing stress. The model for plastic flow of PVC suggested here assigns the extension of the twisted zigzag molecular conformation to creep in stage I. In stage I1 creep is controlled by the reorientation of molecular segments by rotation from initially random orientations in a direction parallel to the principal tensile axis. y Irradiation of the samples before testing increased the steady creep rate and reduced the creep lifetime. This was attributed to chain scission and greater mobility of the molecular segments.