Wave slamming was simulated by repeatedly slamming rectangular sandwich composite specimens mounted on a rigid wedge with constant deadrise angle onto the body of calm water at various energy levels. Under single slamming, peak pressures and strains on the specimens were consistently found near the keel, whereas the maximum damage was localized near the chine. Significant reduction in strength was observed resulting from a single slam even at a moderate slamming energy level that left no apparent/visible damage to the test panel. Similarly, a substantial reduction in strength was observed under repeated slamming at various energy levels. The results were corroborated with acoustic emission observations that indicated a substantial reduction in AE activity in slammed specimens. A methodology was developed for the quantitative assessment of remaining strength and damage accumulation in slammed specimens using AE technique. Face yielding and core crushing were found to be the dominant modes of failure.

The mechanical properties of the glass fiber reinforced Polyamide (PA6) composites made by prepreg tapes and commingled yarns were studied by in-plane compression, short-beam shear, and flexural tests. The composites were fabricated with different fiber volume contents (prepregs-47%, 55%, 60%, and commingled-48%, 48%, 49%, respectively) by using vacuum consolidation technique. To evaluate laminate quality in terms of fiber wet-out at filament level, homogeneity of fiber/matrix distribution, and matrix/ fiber bonding standard microscopic methods like optical microscopy and scanning electron microscopy (SEM) were used. Both commingled and prepreg glass fiber/PA6 composites (with V f 48%) give mechanical properties such as compression strength (530-570 MPa), inter-laminar shear strength (70-80 MPa), and transverse strength (80-90 MPa). By increasing small percentage in the fiber content show significant rise in compression strength, slight decrease in the ILSS and transverse strengths, whereas semipreg give very poor properties with the slight increase in fiber content. Overall comparison of mechanical properties indicates commingled glass fiber/PA6 composite shows much better performance compared with prepregs due to uniform distribution of fiber and matrix, better meltimpregnation while processing, perfect alignment of glass fibers in the composite. This study proves again that the presence of voids and poor interface bonding between matrix/fiber leads to decrease in the mechanical properties. Fractographic characterization of postfailure surfaces reveals information about the cause and sequence of failure. POLYM. COMPOS., 00:000-000,

Foam core sandwich composite panels were slammed onto the body of calm water as a function of slamming energy (161-779 J) and deadrise angle (0 -45 ). Higher slamming energy and lower deadrise angle resulted in greater damage to the material. Discrete pressure data though critical in ship design, failed to yield any relevant damage information. Catastrophic failure was observed to occur beyond a threshold strain of 0.0035 mm/mm. With the introduction of a hydroelasticity function, quasi-static analysis accurately predicted strain behavior under slamming. Post-failure analysis of noncatastrophically damaged specimens indicated very little reduction in flexural capacity in spite of a measurable change in the acoustic emission activity. Core shear along the interface with the facesheets and local buckling of the facesheet and resin fragmentation were observed to be the dominant modes of failure under slamming.

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The study of hydrogen permeation behavior in Armco-Fe showed that 0.1 M H 2 SO 4 was a more effective medium for cathodic polarization compared to 0.1 M NaOH. When both electrolytes were ''poisoned'' with 1.00 g/L Na 2 HAsO 4 AE 7H 2 O, as hydrogen recombination inhibitor, the corresponding hydrogen permeation levels were 3.5 · 10 -5 A/cm 2 in 0.1 M H 2 SO 4 while 0.75 · 10 -5 A/cm 2 in 0.1 M NaOH. The breakthrough times were less than 30 s in 0.1 M H 2 SO 4 , while about 100 s in the NaOH. With varying amounts of ''poisons'', peak permeation of hydrogen (1.75 · 10 -5 A/cm 2 ) was achieved with 10 g/L Na 2 HAsO 4 AE 7H 2 O in 0.1 M H 2 SO 4 , while the least permeation resulted with 10 g/L (NH 2 CSH 2 ) Thiourea addition for same level of 1.00 mA/cm 2 cathodic polarization.