Techno Press
Tp_Editing System.E (TES.E)
Login Search


scs
 
CONTENTS
Volume 17, Number 2, August 2014
 

Abstract
The demand on using more and more advanced composite materials in engineering applications, especially in aerospace applications, have increased substantially in the past decade in Eastern Asia. There is no doubt that this trend will continue and intensify for the coming decade. This special issue covers contributions from scientists and researchers with their latest work in the fields of modeling, verification and validation of advanced composite structures. The Paper 1 introduces the damage of scarf-repaired composite laminates subject to low-velocity impact. Paper 2 is on the experimental study on fatigue crack propagation of fiber metal laminates. Paper 3 is on the constitutive model coupled with damage for carbon manganese steel in low cycle fatigue. Paper 4 is on the test and modeling of low velocity impact on a foam core composite sandwich panel. Paper 5 is on the shape memory properties of thermally activated SMPs-based composites. Paper 6 is on residual stress in SiC fiber reinforced titanium matrix composites. As the guest editor, I would like to thank the Editorial Board of Journal of Steel and Composite Structures for providing the great opportunity to publish these contributions in this special issue. I also would like to thank in particular the technical editor, Ms. S.M. Kim, and reviewers who have been involved in the peer review process of these papers. Without their efforts and helps, the publication of this issue is surely not possible.

Key Words
-

Address
School of Astronautics, Northwestern Polytechnical University, Xi'an, China.

Abstract
This study aimed to investigate the fatigue crack growth behavior of a kind of fiber metal laminates (FML) under four different stress levels. The FML specimen consists of three 2024-T3 aluminum alloy sheets and two layers of glass/epoxy composite lamina. Tensile-tensile cyclic fatigue tests were conducted on centrally notched specimen at four stress levels with various maximum values. A digital camera system was used to take photos of the propagating cracks on both sides of the specimens. Image processing software was adopted to accurately measure the length of the cracks on each photo. The test results show that: (1) a-N and da/dN-a curves of FML specimens can be divided into transient crack growth segment, steady state crack growth segment and accelerated crack growth segment; (2) compared to 2024-T3 aluminum alloy, the fatigue properties of FML are much better; (3) da/dN-ΔK curves of FML specimens can be divided into fatigue crack growth rate decrease segment and fatigue crack growth rate increase segment; (3) the maximum stress level has a large influence on a-N, da/dN-a and da/dN-ΔK curves of FML specimens; (4) the fatigue crack growth rate da/dN presents a nonlinear accelerated increasing trend to the maximum stress level; (5) the maximum stress level has an almost linear relationship with the stress intensity factor ΔK.

Key Words
fatigue; experimental study; fiber metal laminates; crack growth rate; stress intensity factor

Address
(1) Zonghong Xie, Fei Peng:
School of Astronautics, Northwestern Polytechnical University, Xi'an, China;
(2) Tianjiao Zhao:
AVIC the First Aircraft Institute, Xi'an, China.

Abstract
A finite element model with the consideration of damage initiation and evolution has been developed for the analysis of the dynamic response of a composite sandwich panel subject to low velocity impact. Typical damage modes including fiber breakage, matrix crushing and cracking, delamination and core crushing are considered in this model. Strain-based Hashin failure criteria with stiffness degradation mechanism are used in predicting the initiation and evolution of intra-laminar damage modes by self-developed VUMAT subroutine. Zero-thickness cohesive elements are adopted along the interface regions between the facesheets and the foam core to simulate the initiation and propagation of delamination. A crushable foam core model with volumetric hardening rule is used to simulate the mechanical behavior of foam core material at the plastic state. The time history curves of contact force and the core collapse area are obtained. They all show a good correlation with the experimental data.

Key Words
composite sandwich panel; crushable foam core model; low-velocity impact; delamination

Address
School of Astronautics, Northwestern Polytechnical University, Xi'an, China.

Abstract
This study aimed to theoretical calculate the thermal residual stress in continuous SiC fiber reinforced titanium matrix composites. The analytical solution of residual stress field distribution was obtained by using coaxial cylinder model, and the numerical solution was obtained by using finite element model (FEM). Both of the above models were compared and the thermal residual stress was analyzed in the axial, hoop, radial direction. The results indicated that both the two models were feasible to theoretical calculate the thermal residual stress in continuous SiC fiber reinforced titanium matrix composites, because the deviations between the theoretical calculation results and the test results were less than 8%. In the titanium matrix composites, along with the increment of the SiC fiber volume fraction, the longitudinal property was improved, while the equivalent residual stress was not significantly changed, keeping the intensity around 600 MPa. There was a pronounced reduction of the radial residual stress in the titanium matrix composites when there was carbon coating on the surface of the SiC fiber, because carbon coating could effectively reduce the coefficient of thermal expansion mismatch between the fiber and the titanium matrix, meanwhile, the consumption of carbon coating could protect SiC fibers effectively, so as to ensure the high-performance of the composites. The support of design and optimization of composites was provided though theoretical calculation and analysis of residual stress.

Key Words
titanium matrix composites; thermal residual stress; coaxial cylinder model; finite element model; theoretical calculation

Address
(1) Haitao Qu, Hongliang Hou, Bing Zhao:
Beijing Aeronautical Manufacturing Technology Research Institute, Beijing 100024, China;
(2) Song Lin:
Shijiazhuang Tiedao University, Shijiazhuang 050043, China.

Abstract
Carbon-manganese steel A42 (French standards) is used in steam generator pipes of nuclear center and subject to low cycle fatigue (LCF) loads. In order to obtain the material LCF behavior, the tests are implemented in a hydraulic fatigue machine. The LCF plastic deformation and cyclic stress in macroscope have been influenced by the accumulated low cycle fatigue damage. The constitutive kinematic and isotropic hardening modeling is modified with coupling fatigue damage to describe the fatigue behavior. The improved model seems to be good agreement with the test results.

Key Words
low cycle fatigue; fatigue damage; carbon manganese steel; plastic deformation

Address
(1) Zhiyong Huang, Qingyuan Wang:
School of Aeronautics and Astronautics, Sichuan University, No. 29 Jiuyanqiao Wangjiang Road, Chengdu, 610064, China;
(2) Daniele Wagner, Claude Bathias:
Université ParisOuest Nanterre La Défense, 50 rue de Sèvres, Ville d'avray, 92410, France.

Abstract
The damage characters of scarf repaired composite laminates subjected to low-velocity impact with various energy levels at different locations are studied experimentally. The results are compared with those of the original laminates which have no initial damage and don

Key Words
composite laminates; scarf-repair; low-velocity impact; damage; compressive strength

Address
(1) Xiaoquan Cheng, Wenyi Zhao, Shufeng Liu, Yunyan Xu:
School of Aeronautical Science and Engineering, Beihang University, Beijing 100191, China;
(2) Jianwen Bao:
Beijing Institute of Aeronautical Materials, Beijing 100095, China.


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com