In this study, the mechanical properties of plain woven jute-epoxy composite materials were investigated after filling graphene nanoplatelets (GNPs) in different proportions. The time dependent changes in the viscosity and temperature of unfilled epoxy resin, with 0.5, 1 and 2 wt.-% graphene nanoplatelets filled epoxy resins were observed. Woven jute reinforced unfilled, 0.5 wt.-% GNPs filled and 1 wt.-% GNPs filled epoxy composite plates were produced by using vacuum assisted resin transfer molding (VARTM) at the same waiting and processing times. Specimens were prepared and subjected to tensile and flexural tests according to ASTM D 3039 and ASTM D 790 standards, respectively. Images were taken and evaluated with a scanning electron microscope (SEM) in areas where tensile damage occurred. It was observed that the gap amount between the fiber and the matrix increased and the interface adhesion decreased as the fill amount increased in the composites produced. The testing results indicated that the tensile and flexural properties of composites decreased at 0.5 wt.-% and 1 wt.-% during the GNPs loading as compared to unfilled composites.

Today, 3D manufacturing technologies are shown as candidates to replace traditional manufacturing technologies. In this direction, many studies are carried out to reduce the disadvantages of 3D manufacturing technologies. The first few of these disadvantages are; high production cost, slow production speed, and lower strength values of the produced product compared to traditional methods. Increasing or decreasing the printing speed, which is one of the 3d production parameters, appears as a parameter that will directly affect the strength and production costs of the produced product. For this reason, it is important to determine the effects that may occur on the mechanical properties of the product produced by changing the printing speed in terms of choosing the printing speed according to the intended use of the product. In this study, the effect of desktop Fused Deposition Modelling (FDM) 3D printing speed on mechanical properties was investigated. Tensile test samples were produced using Polylactic Acid (PLA) material at seven different printing speeds using two different 3D printers operated without bed heating. The mass, hardness, surface roughness, and porosity values of the produced samples were determined. Fractured surfaces of the samples were analyzed using Scanning electron microscopy (SEM) images. The results show that an increase in the printing speed decreases the mass, the top surface hardness, and the tensile strength and increases the porosity, the arithmetic average roughness of the products produced with both 3D printers.

Impact is defined as an instantaneous external force applied to a material or structure at low, medium, and high speeds over a very short period of time. In this study, we investigate the impact behavior of glass-epoxy composite (GFRP), carbon-epoxy composite (CFRP), and glass/carbon-epoxy hybrid composite (GCFRP) samples subjected to low-velocity impact testing with varying impact energy levels. Composite plates of 330 × 330 mm² consisting of eight layers were prepared using the VARTM method for impact experiments. Each composite type was tested with impact energy values of 10, 20, 30, and 40 J and their impact behaviors were examined. It was observed that as impact energy increased, the maximum force and the collapse values increased as well. The GFRP composite samples had the highest impact strength, while the GCFRP hybrid composite samples had poorer impact resistance compared to the GFRP composites and better impact resistance compared to the CFRP composites.

Bu çalışmada, Ultimaker 2 Extended 3 boyutu yazıcı ile farklı yazdırma hızlarında (20-40-60-80-100-120-140mm/s), ABS (acrylonitrile butadiene styrene) ve PLA (poly-lactic acid) malzeme kullanılarak çekme test numuneleri üretilmiştir. Yazdırma hızının, mekanik özellikler üzerindeki etkisi araştırılmıştır. Üretilen numunelerin kütleleri, sertlikleri ve yüzey pürüzlülükleri ölçülmüş, porozite değerleri hesaplanmış ve üretilen numunelere çekme testi yapılmıştır. Çekme testi sonrasında kopmuş numunelerin kopma bölgelerinden taramalı elektron mikroskobu (TEM) ile görüntüler alınmıştır. Her iki malzeme ile aynı parametrelerde üretilen numunelerin mekanik özellikleri kıyaslanmıştır. Sonuç olarak; PLA malzeme ile üretilen numunelerin çekme mukavemetlerinin ABS malzeme ile üretilen numunelerden daha yüksek olduğu, ABS malzeme ile üretilen numunelerin kopma uzaması değerlerinin de PLA malzeme ile üretilen numunelerden daha yüksek olduğu tespit edilmiştir.

Single-lap joint (SLJ) geometry is the most widely used type of adhesive joint geometry. In this joint, peel stresses occur at the overlap ends due to load eccentricity and the presence of shear-free adhesive termination surfaces. These peel stresses, along with the transverse tensile stresses which occur along the overlap longitudinal axes, and adhesive shear stresses, ultimately cause joint failure. Obviously, reductions in these stresses should result in higher joint strength and increased load capacity. To this end, we exploited elastic spring-back capability of (steel) metal adherends by initially forming curved segments of varying arc lengths and radii at overlap ends. These adherends with curved-end sections were then bonded in single-lap configuration, simply by applying sufficient bonding pressure to elastically flatten the curved segments to result in typically flat overlap sections subsequent to adhesive cure and the removal of bonding pressure. Since the elastic adherend overlap ends tend to revert back to their initial curved form, they exert compressive residual stresses on the adhesive layer in the overlap end regions. We determined that the compressive residual stresses induced in this fashion considerably increased the load capacity of SLJs subjected to tension.

In this work, elasto-plastic stress analysis of single lap joints with and without protrusion in adhesive bondline subjected to tension and bending was carried out using 2D non-linear finite element analysis and confirmed experimentally. AA 2024-T3 aluminum adherends were bonded with SBT 9244 film adhesive. The protrusion was obtained by extending the adhesive film by 2 mm from the overlap length at both overlap ends. Three different adherend thicknesses and overlap lengths for each loading and bondline type were used. The joints with and without protrusion, for comparison, were loaded with the same load for each adherend thickness and overlap length. Finally, it was observed that the protrusion reduces the strength in the joint under tension, while the protrusion increases the strength in the joint under bending.