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CONTENTS
Volume 2, Number 2, May 2020
 

Abstract
The offshore and marine industry has started to use lightweight composites since 1950s and this trend is rising as the exploration of oil and gas is towards deeper water. The fatigue performance has always been a critical issue to ensure the safety of the offshore and marine structures, since the harsh environment and working status make some of these structures subjected to long-term cyclic loading during the service life of 20 to 30 years. This paper performs a literature review on lightweight composites in the offshore and marine industry from the fatigue perspective. The paper first presents the previous investigations on the fatigue failure mechanism and fatigue life prediction models of FRP composites from the material level. Subsequently, the paper reviews the existing studies on the fatigue performance of lightweight composites applied in offshore and marine industry, such as composite risers, composite repair system and other related applications. Finally, the comprehensive review identifies the key challenges in investigating the fatigue performance of composite structures in offshore and marine industry.

Key Words
lightweight composites; FRP; fatigue; offshore and marine industry

Address
Zhenyu Huang:Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Shenzhen University, Shenzhen, 518060, China; Department of Civil and Environmental Engineering, National University of Singapore, 1 Engineering Drive 2, 1175762, Singapore
Wei Zhan: Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Shenzhen University, Shenzhen, 518060, China; Department of Civil and Environmental Engineering, National University of Singapore, 1 Engineering Drive 2, 1175762, Singapore
Xudong Qian: Department of Civil and Environmental Engineering, National University of Singapore, 1 Engineering Drive 2, 1175762, Singapore

Abstract
Nowadays, the use of carbon fiber reinforced plastics (CFRP) plates for strengthening and repairing of structures degraded by their environment have attracted growing interest and are considered to be the most promising materials for applications in structural engineering. One of the main features of the reinforced beam is the significant stress concentration in the adhesive at the ends of CFRP plate; consequently, debonding failure may occur at the plate ends due to a combination of high shear and normal interfacial stresses. These stresses between a beam and a soffit plate, within the linear elastic range, have been addressed by numerous analytical investigations. This paper provides an analytical model for prediction of interfacial stresses in a reinforced steel beam under mechanical as well as thermal loads. The combined effects of the interface slip and both adherend shear deformations on the structural behavior are also incorporated in the current investigation. The present new model needs only one differential equation to determine both shear and normal interfacial stress whereas the others solutions need two differential equations. To verify the validity of the present model, the results are compared with those available in the literature. The effects of the physical and geometric parameters of the CFRP plate and adhesive layer on the maximum values of the interfacial stresses distributions are investigated.

Key Words
bi-material interface; adhesive bonding; thermal effects; interface slip; externally bonded plates; interfacial stresses; adherend deformation; strengthening

Address
Ismail Bensaid: IS2M Laboratory, Faculty of Technology, Mechanical engineering Department, University of Abou Beckr Belkaid (UABT), Tlemcen, Algeria
Bachir Kerboua: Faculty of Technology, Mechanical engineering Department, University of Abou Beckr Belkaid (UABT), Tlemcen, Algeria
Mohamed Azzeddine Kadache: IS2M Laboratory, Faculty of Technology, Mechanical engineering Department, University of Abou Beckr Belkaid (UABT), Tlemcen, Algeria

Abstract
In this article, stress analysis of laminated composite and sandwich cylindrical shells is presented using equivalent single layer higher-order shell theories. A theoretical unification of the several shell theories is presented using a generalized shell theory. A theory is independent of the choice of shape function associated with the transverse shear stress. The present theory satisfies traction free conditions on the top and bottom surfaces of the shell. The principle of virtual work is employed to formulate governing equations and boundary conditions. Closed-formed analytical solutions are obtained using the Navier\'s solution technique. Numerical results are obtained for simply supported laminated composite and sandwich cylindrical shells.

Key Words
a generalized shell theory; laminated; sandwich; cylindrical shells; stress analysis

Address
Atteshamuddin S. Sayyad: Department of Civil Engineering, SRES\'s Sanjivani College of Engineering, Savitribai Phule Pune University, Kopargaon-423601, Maharashtra, India
Yuwaraj M. Ghugal: Department of Applied Mechanics, Government College of Engineering, Karad-415124, Maharashtra State, India

Abstract
This work presents a modified Fourier-Ritz approach for first time is used to study dynamic transverse response of laminated plates with different boundary conditions based on classical plate\'s theory. The transverse displacement component of the plate is represented by Fourier series which is modified by adding auxiliary functions to cosine series so as to accelerate the convergence of the series and the solution, proposed by (W.L. Li, Journal of Sound and Vibration, 273, 619–635, 2004) is corrected in present work. Different boundary conditions, types of lamination cross and angle ply, material types, range of force frequency and thickness schemes, are investigated flexibly and the results are in good agreement with those obtained by other solution techniques.

Key Words
forced vibration; Ritz method; laminated plates; general boundary conditions

Address
Zainab Abdul Kareem Abed and Widad Ibraheem Majeed: Mechanical Engineering Department, College of Engineering, University of Baghdad, Al-Jadrea Baghdad, Republic of Iraq

Abstract
This article investigates the properties of nanocomposites (NCs) and carbon fiber reinforced hybrid materials from experimental and numerical studies under different thermal conditions. The multi-walled carbon nanotubes (MWCNTs) are reinforced in the epoxy for the preparation of NCs with the help of ultrasonic probe sonicator. Hand layup technique is used for the preparation of NCs and NCs based carbon fiber reinforced polymer (CFRP) with pre-cured epoxy. To study the dispersion and agglomerations of the reinforcement in matrix phase, the images are captured at high magnification for the MWCNTs, NCs and NCs based CFRP based hybrid material system with the help of transmission electron microscopy (TEM) and environmental scanning electron microscopy (ESEM). At different temperatures, the short term creep and frequency scan tests are performed on the dynamic mechanical analyzer-8000 (DMA-8000) for MWCNTs based NCs, and NCs based CFRP material system respectively. The creep compliance is obtained from DMA-8000. The frequency and temperature dependent material properties of NCs based material system have obtained from the numerical analysis. The Saravanos-Chamis micromechanics (SCM) and strength of material (SOM) methods are implemented to determine the material properties of NCs based CFRP material system. Storage modulus and loss factor are determined in order to study the effect of different MWCNT percentage on the NCs based CFRP material systems. Experimental validation has been done for the suggested NCs based CFRP material system. Responses suggest the damping property is improved by the inclusion of MWCNTs in the matrix phase for CFRP material system. It is further observed that the higher MWCNTs percentage in the matrix phase leads to higher stiffness and damping.

Key Words
MWCNTs; nanocomposite; creep compliance; micromechanics; damping

Address
S. Srikant Patnaik, Ashirbad Swain and Tarapada Roy: Department of Mechanical Engineering, National Institute of Technology Rourkela, Rourkela-769008, India


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