Browsing by Author "Ali, Hafiz Qasim"

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APPLICATION OF HOOKE’S LAW TO ANGLE PLY LAMINA
(ESKİŞEHİR TEKNİK ÜNİVERSİTESİ, 2022) Yılmaz, Çağatay; Ali, Hafiz Qasim; Yıldız, Mehmet; 0000-0002-8063-151X; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Yılmaz, Çağatay
Aerospace-grade carbon fiber reinforced polymer composite plates with four different fiber orientations 0º, 30º, 45ºand 60º is produced with the autoclave curing method and subjected to tensile testing. The stress-strain curves of the composite specimens are compared with Hooke’s law. It is observed that Hooke’s law coincides precisely with the experimental results for samples containing fibers parallel to the loading direction. However, it does not coincide with samples where the fibers make a certain angle with the applied load direction. Moreover, it is reported that Hooke’s law converges the experimental results for small strain values but diverges significantly from the experimental results at higher strain values.
The effect of different tabbing methods on the damage progression and failure of carbon fiber reinforced composite material under tensile loading
(ELSEVIER SCI LTD, 2022) Yılmaz, Çağatay; Ali, Hafiz Qasim; Yıldız, Mehmet; 0000-0003-1626-5858; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Yılmaz, Çağatay
Composites are well-known and widely used materials due to their anisotropic nature and high strength-to-weight ratio; therefore, the mechanical performance of these materials is crucial. Precise tensile testing is essential to obtain material properties that are crucial for the design stage of composite structures. This study is an effort to investigate the effect of adhesive materials used for tabbing process, which is necessary for the tensile testing procedure. Araldite and AF 163-2k film are used as the adhesive film, whereas in the case of AF 163-2k, tabbing is done through two different procedures (Jig and corner holes method). Apart from the tensile performance, strain distribution and damage progression are monitored simultaneously using digital image correlation (DIC) and acoustic emission (AE) analysis. It is observed that there is no significant difference in the ultimate tensile strength of these composites tabbed with different adhesives and procedures. Nevertheless, the first major failure strength is much higher in Araldite tabbed specimens compared to AF 163-2k film (the first major failure activity is defined as a point at which material loses its integrity, especially when considering structural or aerospace applications). Also, strain distribution throughout the gauge length recorded via DIC is appreciably different, which is attributed to damage accumulation and progression monitored by AE analysis. The frequency-based analysis of AE data is performed to classify the damage, and cumulative energy is correlated with the DIC to navigate the failure activity at different times and stress levels.
Monitoring and verification of micro-strain generated inside the laminate subjected to thermal loading through fiber bragg grating sensors and classical laminate theory
(WILEY, 2023) Yilmaz, Cagatay; Ali, Hafiz Qasim; Yildiz, Mehmet; 0000-0002-8063-151X; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Yilmaz, Cagatay
Fiber Bragg Grating (FBG) sensors possess enormous potential for the cure monitoring and integrity assessment of Carbon Fiber Reinforced Polymer (CFRP) composites. These sensors can be embedded inside the structure to monitor the strain in the desired region of interest. The strain on an FBG sensor can be calculated by measuring the change in the center wavelength of the sensor. This change in center wavelength is a function of temperature and mechanical strain. Therefore, temperature compensation is necessary for a precise mechanical strain measurement with an FBG sensor. In this study, FBG sensors are embedded in different layers of the CFRP laminate to record the mechanical strain caused by the thermal expansion, which happens under the influence of temperature. Classical laminate theory (CLT) is implemented to assess the accuracy of FBG sensor measurements and the strain data acquired from both FBG sensor and CLT correlates. Furthermore, a resistive strain gauge is deployed to measure the strain under the influence of temperature. It is depicted that strain values recorded by the strain gauge under the influence of the temperature do not agree with the strain measured by CLT, and an error of 150% occurs among their values.