In the present paper, changes in the residual stress of carbon/epoxy laminated composites as a result of
adding graphene nanoparticles (GNPs) content were studied theoretically and experimentally. Three dissimilar weight
fractions of GNPs, i.e., 0.1%, 0.25% and 0.5%, were added into an epoxy matrix. Unidirectional carbon fibers (CFs)
were used as reinforcement to fabricate cross-ply laminated composites. Mechanical and thermal properties of the
GNP/epoxy nanocomposites were then characterized via tensile tests as well as thermomechanical analysis (TMA).
Based on experimental observations, adding even small fractions of GNP to epoxy matrix caused to decrease in the
coefficient of thermal expansion (CTE) significantly while the epoxy resin Young

https://www.techno-press.org/download.php?journal=cme&volume=2&num=1&ordernum=5

Effects of adding graphene nanoparticles in decreasing ofresidual stresses of carbon/epoxy laminated composites

Residual stress measurement is of utmost importance for the safety and reliability of engineering components and has been an active area of scientific research. Relaxation techniques such as hole drilling, slitting and ring core method are widely applied semi destructive techniques for residual stress measurements in polymer composites. This article reviews the recent literature on the measurement of residual stress in polymer composite by employing the above-mentioned relaxation techniques. This article summarizes the categories of residual stresses, causes of formation, techniques of measurements and also briefly outlines the chronological developments of the Hole drilling and slitting method. The article also provides a comparative summary of these relaxation methods.

An Assessment on Residual Stress Measurement in FRP Composites Using Relaxation Techniques

The energy release rate for delamination in a laminated composite is supposed to be the material property being considered as independent of non-material property variables. However, Mode I fracture toughness (GI) is found to vary with lamina arrangement, geometrical dimensions, and process-induced stresses. In this investigation, the influence of lamina stacking arrangement on process-induced stresses and their effects on GI of laminated composites are studied. Unidirectional (UD) ([0]16) and cross-ply ([902/06]s, [904/04]s, and [906/02]s) glass/ epoxy (GE) composites with the delamination plane at 0◦//0◦ were prepared by manual layup method and post-cured at 120°C for 4 hours. GI of composite laminates were experimentally determined using a double cantilever beam (DCB) specimen as per ASTM D 5528. The slitting method was applied to determine the process-induced stresses in GE laminates. The stacking sequence of laminas was found to have a noticeable effect on the state of residual stresses and GI of GE laminates. Residual stresses do not have much influence on the GI for delamination initiation, whereas GI for the crack propagation was found to increase with a gradual increase in compressive residual stresses

Effect of Ply Orientation on Residual Stresses and Their Influence on Mode I Fracture Toughness of Glass-Epoxy Composites with 0°//0° Crack Interface

C T Predictive maintenance techniques are developed to help determine the condition of in-service equipment in order to predict when maintenance should be performed. There is a need for cost-performance effective approaches and methods for predictive maintenance that can make non-destructive on-site measurements to predict residual stress-induced critical faults in large metal structures, such as ships. In this study, an optical method based on the calculation of the non-destructive surface magnetic permeability coefficient is proposed for monitoring the residual stress distribution in AISI4040 and DUPLEX materials. In our proposed new method for determining theoretically the residual stress at the joint site of large plates in ships, the Lorentz-Drude model and the Fresnel approximation were used. Our results show that the new optical technique proposed in this study is sufficient and thriving for the determination of residual stresses in large

Umarfarooq Maktedar Abdulkhadar

Papers

An Assessment on Residual Stress Measurement in FRP Composites Using Relaxation Techniques

Effect of Ply Orientation on Residual Stresses and Their Influence on Mode I Fracture Toughness of Glass-Epoxy Composites with 0°//0° Crack Interface