This paper addresses the effects of different stacking sequences and seawater on the buckling behavior of hybrid composite plates. For the buckling tests, 12-layered hybrid composite plates were produced using different combinations of carbon, E-glass and aramid fibers, with an epoxy resin system as the matrix (Araldite LY1564/Aradur 3486). The hybrid composite plates were designed at the symmetric orientation angles of [(0/90)3]s, [(30/−60)3]s, [(45/−45)3]s and an anti-symmetric orientation angle of [(0/90)3]2. The hybrid composite samples were divided into groups and were subjected to buckling tests after being kept in different settings for varying periods of time (room temperature for 90 days, Black Sea water for 90 days, Mediterranean Sea water for 90 days, Mediterranean Sea water for 150 days). In light of the data obtained from the tests, the buckling behaviors of the layered hybrid composite plates were examined. The highest critical buckling load occurred in the carbon/aramid/glass (CAG) hybrid samples with the stacking sequence of [(0/90)3]s, whereas the lowest critical buckling load occurred in the carbon/aramid/glass (CAG45) hybrid samples with the stacking sequence of [(45/−45)3]s. It was observed that the critical buckling loads of the samples immersed in seawater decreased when compared to the critical buckling loads of the samples kept at room temperature. It was also found that the critical buckling loads of the hybrid samples immersed in the Mediterranean Sea water, which has high salinity, were lower than the critical buckling loads of the hybrid samples immersed in the Black Sea water, which has lower salinity.

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This study considers the bearing strengths and failure modes of woven-glassepoxy prepreg composite mechanically fastened joints. For the study, the specimens were immersed in natural seawater in the laboratory for over 1 year. The edge distance-to-hole diameter (E/D) ratio and the specimen width-to-hole-diameter ratio (W/D) were systematically altered during experiments. Failure modes were determined by observing the failure regions on the specimens. Damage progression in pin-loaded specimens prepared from woven-glassepoxy prepreg was also examined using a scanning electron microscopy for three different percentages of ultimate failure load. According to the experimental investigation results, it was observed that the bearing load values obtained from the specimens immersed in seawater decreased considerably in comparison to unimmersed specimens.

In the present study, an elastic-plastic stress analysis is carried out on a high-density thermoplastic-based composite cantilever beam loaded by a single force at its free end. An analytical solution is performed for satisfying both the governing differential equation in the plane stress case and boundary conditions for small plastic deformations. The solution is carried out under the assumption of the Bernoulli-Navier hypotheses. The composite material is assumed to be strainhardening. The Tsai-Hill theory is used as a yield criterion. The residual stress component of x are determined for 0, 30, 45, 60 and 90 orientation angles. It is found that the intensity of the residual stress is maximum at the upper and lower surfaces of the beam. The horizontal displacement component of u is greater than the vertical displacement component of v.

In the present study, a thermal elastic-plastic stress analysis is carried out on simply supported symmetric cross-ply [0/90]2 and angle-ply [30/30]2, [45/45]2, and [60/60]2 thermoplastic laminated plates. The temperature changes parabolically along the thickness of the plates. It is T0 and T0 at the upper and lower surfaces, respectively. The composite material is assumed to be linear strain hardening. An analytical solution is performed for satisfying the thermal elastic-plastic stress-strain relationship and boundary conditions for small plastic deformations. The Tsai-Hill theory is used as a yield criterion. The elastic-plastic solution is carried out for small plastic deformations. The residual stress distributions along the thickness of the plates are obtained.