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Abstract: Investigating the fatigue behaviour of a material often requires a lot of experiments in order to have statistically valid results. However, the number of successful fatigue experiments, where tab failure did not occur, can be significantly smaller than the total number of experiments. This manuscript studies the fatigue behaviour of a carbon fabric reinforced PPS using the specimen geometry proposed by ASTM D3479/D3479M. All specimens failed in the tabbed section, meaning that fatigue life may be significantly underestimated and the proposed geometry needs improvement. Therefore, the main emphasis of this manuscript is on stiffness reduction and permanent deformation of the material, rather than on the number of cycles to failure. It may be concluded that for the [(0°,90°)]4s stacking sequence the material does not show significant stiffness reduction and that only limited permanent deformation is present. Furthermore, the material shows very brittle failure behaviour and the stress-span between infinite fatigue life and failure in a few dozen cycles is very narrow. [Copyright &y& Elsevier]

Abstract: Observations are reported on isotactic polypropylene in tensile tests with various strain rates, relaxation tests at various strains, and creep tests with various stresses at room temperature. Constitutive equations are derived for the viscoelastic and viscoplastic responses of semicrystalline polymers at three-dimensional deformations with small strains. The stress–strain relations involve eight material constants that are found by fitting the experimental data. The model is applied to the numerical analysis of creep failure of polypropylene under various deformation modes (uniaxial tension, equi-biaxial tension, shear, multiple-step creep tests). [Copyright &y& Elsevier]

Abstract: Low-velocity impact tests on cast acrylic (PMMA) plates were conducted using an instrumented drop-weight impact machine under various temperatures. Radial cracks were induced and the impact force histories were recorded. Results indicated that there was a glass transition temperature of cast acrylic between 185 and 200°F. Ultrasonic assessments on the impacted acrylic plates were then performed using different transducers. Focused transducers provided more accurate results than flat ones. In addition, the higher the ultrasound frequency, the better the resolution. Finally, the drop-weight impact responses were simulated using LS-DYNA. Two node-splitting techniques, sudden releasing and stepwise releasing, based on maximum tensile stress failure criterion, were implemented for this study. The maximum tensile stress failure criterion was adopted to capture the onset of crack initiation and crack propagation. The node release methods enabled us to calculate the strain energy release rates of cast acrylic. Numerical simulations were compared with experimental results and good agreements were achieved. [Copyright &y& Elsevier]

Morphology and deformation mechanisms and tensile properties of tetrafunctional multigraft (MG) polystrene-g-polyisoprene (PS-g-PI) copolymers were investigated dependent on PS volume fraction and number of branch points. The combination of various methods such as TEM, real time synchrotron SAXS, rheo-optical FTIR, and tensile tests provides comprehensive information at different dimension levels. TEM and SAXS studies revealed that the number of branch points has no obvious influence on the microphase-separated morphology of tetrafunction MG copolymers with 16 wt % PS. But for tetrafunctional MG copolymers with 25 wt % PS, the size and integrity of PS microdomains decrease with increasing number of branch point. The deformation mechanisms of MG copolymers are highly related to the morphology. Dependent on the microphase-separated morphology and integrity of the PS phase, the strain-induced orientation of the PS phase is at different size scales. Polarized FT-IR spectra analysis reveals that, for all investigated MG copolymers, the PI phase shows strain-induced orientation along SD at molecular scale. The proportion of the PI block effectively bridging PS domains controls the tensile properties of the MG copolymers at high strain, while the stress−strain behavior in the low-mediate strain region is controlled by the continuity of PS microdomains. The special molecular architecture, which leads to the higher effective functionality of PS domains and the higher possibility for an individual PI backbone being tethered with a large number of PS domains, is proposed to be the origin of the superelasticity for MG copolymers. [ABSTRACT FROM AUTHOR]