Luffa cylindrica of Turkey's Aegean Region was evaluated in terms of fiber characterization and the mechanical properties of its composite with polyester. Characterization of Luffa cylindrica was carried out by Fourier transform infrared spectrophotometer, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, and thermogravimetric analysis. Cellulose, hemicellulose, and lignin contents of Luffa cylindirica were also determined. Deconvolutions of XPS data enable determining the distributions of functional groups on the surface of Luffa cylindrica. Luffa cylindrica-reinforced polyester composite was subjected to water aging under a steam of seawater containing 5% sodium chloride for 170 h at 50 C. After water aging, tensile strength, flexural strength, interlaminar shear strength, and tensile elongation at break values of the composite decreased $ 28%, 24%, 45%, and 31%, respectively. However, tensile modulus and flexural modulus did not change significantly.

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This study analyzes the influence of different talc ratios on weld strength of polypropylene joined with hot plate welding process. It further determines the optimum welding parameter settings to achieve the optimum weld strength and observes the effect of process parameters, namely plate temperature and heating time on the joint quality. Process parameters were considered as variables and their effect, interactions and relative significance were investigated by utilizing design of experiment. Simultaneously, a mathematical predictive model of the weld strength was developed in terms of welding parameters. The model can predict effectively weld strength with a 95% confidence level.

Mechanical performances of six sandwich type T-joints, used in marine applications subjected to tensile load, have been investigated both numerically and experimentally in this study T-joints, each with different geometries, have been manufactured, Type A: continuous core in join with right angle; Type B: core removed at joint; Type C: core with wedge fillet; Type D: core with 25 mm radius fillet; Type E: core with 70 mm radius fillet and Type F: DK-CND1 of Toftegaard and Lystrup with overlaminate. The skin was a 5mm thick orthophitalic polyester/glass laminated composite and the core was PVC (Divinycell H80). Due to absolute values of the maximum strain values of the T-joints, Type E shows promising performance under tension while Type B is the weakest. It is not recommended to use Type B in the structures subjected to tension. Grading from the strongest to the weakest of T-joints is Type C, D, A and F. Results of the numerical modelling and tests also affirm the utility of the 2D FE models for further studies of the strain distribution in such sandwich T-joints.

Steel structures coated with fiber-reinforced polymer (FRP) composites have gained wide acceptance in marine industry due to their high strength-to-weight ratio, good protection from environmental degradation, and impact loads. In this study, adhesive bonding performance of single-lap bonded joints composed of steel coated with FRP has been investigated experimentally for three different surface roughness and two epoxy types. Single-lap bonded joints have been tested under tensile loading. The adhesive bonding performance has been evaluated by calculating the strain energy values. The results reveal that the surface roughness of steel has a significant effect on the bonding performance of steel to FRP combinations and the performance of the resin can be improved by using the primer in an economical way.