Effect of Barium Titanate Reinforcement on Tensile Strength and Dielectric Response of Electrospun Polyvinylidene Fluoride Fibers

In this study, we used electrospinning to obtain polyvinylidene fluoride (PVDF) fibers reinforced with barium titanate (BaTiO3) and investigated the influence of BaTiO3 concentration on the tensile strength and dielectric behavior of PVDF fibers. X-ray diffraction (XRD) study and infrared spectroscopy revealed that PVDF fibers filled with BaTiO3 possessed higher fraction of ferroelectric β-crystals compared to neat PVDF fibers. Further, incorporation of 40 wt% BaTiO3 within the fibers increased their stiffness and strength by 95 and 38%, respectively. These improvements in tensile properties of BaTiO3 filled PVDF fibers arose from the reinforcement effect of BaTiO3. Also, the dielectric response of the BaTiO3/PVDF fibers was characterized. The effective dielectric constants of PVDF fibers reinforced with BaTiO3 were found to increase consistently with BaTiO3 content at all frequencies. The dielectric loss of the fibers did not show any significant change for all concentrations of BaTiO3 within the fibers

Temperature and rate dependent fracture in glass-filled polystyrene

The rate and temperature dependent fracture behavior of glass-filled polystyrene has been investigated over the crack speed range of 10 13 to 1 mm/sec and in the temperature range 283 to 396°K for three environmental conditions: (i) air; (ii) water; and (iii) hot water exposure at 363°K and subsequent drying. Relationships between fracture toughness ( K c ), crack speed and temperature have been obtained experimentally and analysed according to the concepts of fracture mechanics and reaction rate theories. Crack propagation in air is shown to be controlled by a Β-relaxation process associated with crazing. Activation energies of 200 ∼ 210 kj/mole in air and 80 ∼ 120 kj/mole in water are reported. At a given temperature and crack speed, the glass-filled polystyrene is shown to display smaller crack propagation resistances in a water environment when compared with the air results. Specimens subjected to hot water exposure and then tested after drying also possess less cracking resistance. This toughness degradation phenomenon is a result of the damaging effects of the water which penetrates into the glass-filled composite.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38103/1/760160604_ftp.pd

Fatigue crack propagation of PMMA in organic solvents

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44786/1/10853_2004_Article_BF00541761.pd

Contoured double cantilever beam specimens for fracture toughness measurement of adhesive joints

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44671/1/10853_2004_Article_BF00540939.pd

Singularities of an interface crack in electrostrictive materials

AbstractIn the present work, the singularities of an interface crack between two dissimilar electrostrictive materials under electric loads are investigated. Within the framework of two-dimensional deformation, the problem is solved using the complex variable method. Three crack models, that is, permeable, impermeable and conducting crack models are considered individually. Complex potentials and intensity factors of total stresses are derived by considering both the Maxwell stresses in the surrounding space at infinity and inside the crack. It is found that, for the above three crack models, the singularities of total stress are the same as those in traditional bi-materials with an interface crack; however, the intensities of the total stress depend on the actual crack model used

Phase behavior and nanomechanical mapping of block ionomer complexes

Block ionomer complexes SSEBS-c-PCL were prepared, as a consequence of proton transfer from the sulfonic acid of sulfonated polystyrene-block- poly(ethylene-ran-butylene)-block-polystyrene (SSEBS) to the tertiary amine of a tertiary amine terminated poly(?-caprolactone) (APCL). The phase behavior of SSEBS-c-PCL was thoroughly investigated and the results showed that APCL in SSEBS-c-PCL displays unique crystallization behavior owing to the influence of interactions between the amine and sulfonic acid groups as well as the effects of confinement. Further, small-angle X-ray scattering study revealed that SSEBS-c-PCL displays a less ordered micro-phase structure compared to SSEBS. A quantitative mapping of mechanical properties at the nanoscale was achieved using peak force mode atomic force microscopy. It is found that the block ionomer complex possesses a higher average elastic modulus after complexation with crystallizable APCL. Additionally, the moduli for both hard and soft phases increase and the phase with higher modulus assignable to the hard SPS component shows much more pronounced changes after complexation, confirming that APCL interacts mainly with the SPS blocks. This provides an understanding of the composition and nanomechanical properties of these new block ionomer complexes and an alternative insight into the micro-phase structures of multi-phase materials