The low-velocity impact and bending performance of adhesive joints are critically important for their reliable use in multiple industrial applications. Enhancements of adhesive joints’ mechanical properties are significantly valuable for the long-term safe use and overall life of structural components. This study investigated the low-velocity impact and bending properties of double strap joints (DSJs) reinforced with graphene nanoplatelets (GNPs). In this context, GNP-reinforced adhesives with 1%, 2%, and 3% reinforcement by weight were prepared, and the dispersion quality of graphene was examined using scanning electron microscopy. Subsequently, graphene-modified DSJs were manufactured and mechanical tests were carried out. Low-velocity impact tests were performed at 5 J and 10 J energies in a single impact configuration. Tests of the nonperforated specimens showed that the contact force increased with graphene reinforcement. The absorbed energy and the contact time of the specimens with the impactor tip decreased with nano reinforcement by 5% and 4%, respectively. Additionally, a significant decrease in the displacement was observed with 2% and 3% graphene reinforcements. Significant improvements of up to 58% were observed in the flexural strength of the joints with graphene reinforcement.

This study performed an experimental modal analysis and investigated the mechanical properties of graphene nanoparticle (GNP)-reinforced, adhesively bonded double strap joints (DSJs). The DP270 structural adhesive was reinforced with graphene nanoparticles by using five different manufacturing methods and bulk specimens were prepared with 1%, 2% and 3% reinforcement by weight. The dispersion of graphene was observed by using scanning electron microscopy (SEM) because its efficient distribution in the adhesive is directly affected by the mechanical and modal properties of the modified polymer. Furthermore, the damping ratios and natural frequencies of the bulk specimens were also determined. Based on the dynamic characteristics and SEM observations, the most appropriate method to manufacture the joints was selected, and DSJs were prepared by using AA 2024-T3 aluminum alloy as the adherend. After that, the modal and tensile properties of the graphene-reinforced DSJs were determined. Consequently, it was observed that a graphene reinforcement ratio of 2% by weight showed a 36% increase in the damping ratio of the adhesive and a 23% increase in the damping ratio of the joint. In addition, it was observed that graphene reinforcement resulted in up to an 81% increase in the failure strength of the modified DSJs.

Son yıllarda geliştirilen yeni üretim metotları ile tabakalı kompozit yapıların kullanım alanları dikkatedeğer bir şekilde artmıştır. Bu yapıların kullanım performanslarını arttırmak amacıyla farklı tekil kumaşlar,farklı diziliş sıraları ile aynı kompozit yapıda kullanılarak hibrit kompozit yapılar elde edilmiştir. Tabakalı hibritkompozit yapıların mekanik özellikleri ile ilgili birçok araştırma yapılmışken dinamik özellikleri ile ilgili yapılanaraştırmalar henüz yeterli değildir. Bu çalışma kapsamında; tekil cam (C) ve tekil karbon (K) elyaflar kullanılarakVARTM (Vakum Destekli Reçine Transfer Kalıplama) yöntemi ile 4 tabakalı, 4 farklı diziliş sırasına sahipnumunelerin üretimi gerçekleştirilmiştir. Bu numuneler; sade cam (C4), sade karbon (K4) olmak üzere iki tekilkompozit yapı ve bu iki elyaf türünün aynı yapı içerisinde simetrik olarak farklı diziliş sıralarıyla kullanılmasıylaelde edilen iki farklı hibrit kompozit yapıdan (KCCK ve CKKC) oluşmaktadır. Üretilen kompozit levhalardan,ilgili ASTM standartlarına göre üç nokta eğilme, çekme ve titreşim testleri için gerekli olan numuneler kesilerekelde edilmiştir. Üç nokta eğilme testleri yapılarak numunelerin maksimum eğilme dayanımları ve çekme testleriyapılarak numunelerin elastisite modülleri belirlenmiştir. Ayrıca ankastre-serbest sınır şartında serbest titreşimanalizleri yapılarak doğal frekans ve sönüm oranı değerleri tespit edilmiştir. Elde edilen sonuçlar ile interply hibritkompozit yapılarda diziliş sırasının maksimum eğilme dayanımı, elastisite modülü ve titreşim özelliklerine etkisiincelenmiştir.

Plate composite structures are used in many sectors today. Therefore, the demand for these structures is increasing. Especially in the field of aerospace, layered composite structures attract more attention. These wide range of applications affect composite materials in various aspects such as dynamic and mechanical in terms of working environments. Time-dependent variable stresses, vibrations and fatigue that occur in structures subjected to dynamic loads adversely affect both the internal and external structure of composite materials. This situation reduces the safe service life of composite materials. It is an important problem to eliminate or minimize the parameters that negatively affect the economic service life of fiber reinforced layered composite structures. In order to overcome these problems, it is aimed to create new composite structures by adding two different thermoplastic veil layers between fiber fabrics, which are widely used on an industrial basis. In this study, carbon fiber was used as the fiber fabric and Polyamide (PA) and Polyether ether ketone (PEEK) veils were used as the thermoplastic veil layers. The productions were made by Vacuum Assisted Resin Transfer Molding (VARTM) method and dynamic (natural frequency and damping ratio) tests were performed according to the relevant ASTM standards. With the experimental results obtained, the dynamic properties of thermoplastic veil-layered carbon fiber/epoxy composites were comparatively investigated to determine the effect of both veil layers and different fiber contents.

In this study, recycled Ti6Al4V alloy powder was utilized as a reinforcement to enhance the mechanical and modal properties of polyurethane foam (PUF) core-based sandwich composites. Sandwich composite having carbon fiber reinforced polymer (CFRP) composite face sheets and Ti6Al4V powder-reinforced PUF cores were manufactured. The PUF cores were reinforced with two different variants of Ti6Al4V powder based on particle sizes from 1 to 3 wt.%. The dispersion quality was investigated using scanning electron microscopy (SEM). A detailed experimental modal analysis was conducted to evaluate the modal properties in terms of the natural frequencies and damping ratios of the sandwich specimens. A comprehensive mechanical study was also conducted in terms of compression, buckling, flexural, and impact tests according to the relative ASTM standards. The experimental results demonstrated that the Ti6Al4V reinforced sandwich specimens exhibited superior mechanical and modal properties with enhanced PUF cores. Improvements in excess of 21%, 37%, and 24% were recorded in the compression, buckling, and flexural response of the reinforced specimens, respectively, compared to those of their neat counterparts. Similarly, remarkable improvements were also observed in the experimental modal and impact properties of the Ti6Al4V alloy powder-reinforced sandwich composites.