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Macromechanical Behavior of a Laminate
Published in Robert M. Jones, Mechanics of Composite Materials, 2018
All strength criteria for composite laminates depend on the strengths in the laminae principal material directions, which likely do not coincide with laminae principal stress directions. Therefore, the strength of each lamina in a laminate must be assessed in a coordinate system that is likely different from those of its neighboring laminae. This coordinate mismatch is but one of the complications that characterizes even a macroscopic strength criterion for laminates. The main factors or elements that are peculiar to laminate strength analysis are shown in several categories in Figure 4-35. There, the cure and use conditions affect the state of the material that is used in the laminate. For example, the difference between the stress-free, elevated-temperature, curing temperature and the service temperature causes thermal or residual stresses. Similarly, the difference between curing moisture content and service moisture content causes moisture stresses as does the difference between moisture contents at any two different times. Moisture diffuses throughout epoxy matrix materials at a far slower rate (months) than temperature (minutes). In some cases, the history of environmental effects such as temperature and moisture must be considered.
Strength criteria for composite material structures
Published in Michael S. Found, Experimental Techniques and Design in Composite Materials 4, 2017
A. De Iorio, D. Ianniello, R. Iannuzzi, F. Penta, A. Apicella, L. Di Palma
The method usually employed to verify the strength of composite laminates is the “ply-to-ply” analysis. If the characteristics of internal reactions Nij, Tij and Mij or the generalized strains εij(0) and kij are known the stress component σij(k) acting on the lamina k of the plate element can be evaluated by means of the lamination theory. Thus it is simple to check the strength of lamina k if its failure envelope is known.
Development of Embedded FBG Sensor Networks for SHM Systems
Published in Jayantha Ananda Epaarachchi, Gayan Chanaka Kahandawa, Structural Health Monitoring Technologies and Next-Generation Smart Composite Structures, 2016
Gayan Chanaka Kahandawa, Jayantha Ananda Epaarachchi, John Canning, Gang-Ding Peng, Alan Lau
The SHM systems used in damage detection in FRP composites must be capable of identifying the complex failure modes of composite materials. The damage accumulation in each layer of a composite laminate is primarily dependent on the properties of the particular layer (McCartney, 1998; McCartney, 2002) and the loads which are imposed onto the layer. As such, the layered structure of the composite laminates makes it difficult to predict the structural behavior using only surface attached sensors. Over the past few years, this issue has been critically investigated by many researchers using embedded FBG sensors (Eric, 1995; Lee et al., 1999; Takeda et al., 2002, 2003, 2008).
Effect of reinforcement phases and post-cure temperature on adhesively bonded hybrid patch repair in indented glass/epoxy composite laminates
Published in The Journal of Adhesion, 2023
Shravan Kumar Chinta, Dilip Sankar S, Bhaskar Nagesh G, Himakarthik R, Naga Rajagopal B, Suresh Kumar C, Sundararaj M
In order to improve the delamination resistance, techniques including Z-pinning [17–19], needling [20,21], and 3D weaving[22] were employed. Tan et al. [23] developed delamination reduction trend (DRT) model to predict stitching efficiency and reduction of delamination area of stitched composites. The similar improvement of interlaminar resistance was obtained between 3D reinforced stitched and weaved composites [22,24]. Velmurugan et al. [25] suggested that the plain stitching can be performed to improve the mechanical properties of composites. Mouritz [26] introduced through thickness stitching to improve the delamination resistance in laminated composites. A resurgence of interest in the use of stitching to improve the damage resistance in composites has been reported in the recent literatures [27–29]. Therefore, stitching can be adopted to improve the interlaminar strength of patch repair in polymer composite laminates.
Vibration energy transfer in variable stiffness laminated composite panel with a cutout
Published in Mechanics of Advanced Materials and Structures, 2023
Chen Zhou, Jian Yang, Yingdan Zhu, Chendi Zhu
Composite laminates are frequently used in civil and mechanical engineering as crucial components of several constructed products used in the automotive, marine, and aerospace industries [1]. Composite materials have superior specific strength, specific stiffness, fatigue resistance, and corrosion resistance when compared to their conventional metal material counterparts. Besides, the composite structure provides a wide range of design options arising from the possibility to alter the fiber orientation and select the fiber and matrix materials [2]. The manufacturing of variable angle tow (VAT) composite materials with continuous curved fibers has been made possible owing to the development of an innovative technique [3]. This implies that the designability of such VAT composite structure has been further enhanced. For example, when fibers are built along the load path of the structure, its carrying capacity might be significantly increased without additional weight.
An overview of fatigue models for composite laminate materials
Published in Mechanics of Advanced Materials and Structures, 2022
Nabilah Azinan, A. Halim Kadarman, Junior Sarjit Singh Sidhu
Composite laminate materials consist of a multi-phase layer of matrix and fiber that are bonded together layer by layer where each layer may have similar or dissimilar material properties with different fiber direction under various stacking sequences [5, 6]. Figure 2 shows the stacking of unidirectional plies to make up a laminate [7]. A common stacking sequence of fiber direction in composite lay-up for aircraft component manufacturing application is [0/+45/-45/90] and [0/90] which are also often called cross-ply composite laminates [4]. Composites with these directions are called quasi-isotropic due to the two-dimensional (2 D) isotropy in the plane in which the mechanical properties which include stiffness and strength are roughly equal when loaded along in any in-plane direction [8]. The stacking sequence in each composite laminate material carry different characteristics of loading, namely, 0° and 90° directions carry tension loading, compression loading, and bending loading, whereas the 45° stacking sequence carry shear loading characteristics [4]. Therefore, the stacking sequence of fibers in composite laminate materials is very influential in the mechanical properties including stiffness and failure properties.