Journal of Aerospace Engineering

An analytical model for the thermomechanical response of metal matrix composites was developed based on the method of cells micromechanics model and classical lamination theory. The inelastic behavior of the matrix material is modeled using either the classical incremental plasticity theory or the Freed-Walker viscoplasticity theory, which is a more recent development designed for use with copper and copper alloys. The composite model was subsequently used to investigate the effect of the matrix constitutive model and the effect of nonuniform fiber distribution, on the thermal expansion of unidirectional graphite/copper (Gr/Cu) composites. Results illustrate that when the viscoplastic model is used, stress relaxation decreases the ability of the copper matrix to support load, and the predicted longitudinal thermal response of the composite resembles that of the graphite fiber. The effect of nonuniform fiber distribution on the longitudinal thermal expansion is more pronounced when the plastic constitutive model is used. In addition, the effect of the nonuniformity is more pronounced for the longitudinal thermal expansion of Gr/Cu than the transverse thermal expansion. The model predictions were compared with experimental thermal expansion data for Gr/Cu, and the use of the viscoplastic constitutive model was found to provide better correlation than the plastic constitutive model.

In this paper, modal analysis experiments on composite plates with and without delaminations are carried out. Specimens of the glass cloth and epoxy matrix composite plate, including plates without delamination and plates with through-width delaminations, are manufactured by the layup technique. A thin Teflon film is used to introduce the delamination during the manufacturing process. Delamination modes are found in delaminated plates by comparing the modal analysis results of the delaminated plates with the results of the nondelaminated plates. The sensitivity of the Teflon in the delamination area to the delamination modes is analyzed by the modal analysis experiments of the plates with Teflon in and out of the delamination area. Two delamination coefficients are defined to discern the delamination modes more quantitatively. According to the modal analysis results, the possibility of detecting the delamination size and location is discussed.

Offshore compliant structures such as guyed platforms, tension leg platforms and articulated towers are economically attractive for deep-water conditions because of their reduced structural weight compared to conventional platforms. The foundations of these kinds of structures do not resist lateral environmental loads forces; instead, restoring moments are provided by a large buoyancy force, a set of guylines or a combination of both. These structures have a fundamental frequency well below the ocean wave's lower frequency bound. As a result of the relatively large displacements, geometric nonlinearity is an important consideration in the analysis of such a structure. This paper presents a literature review on offshore compliant structures. Our purpose for this paper was to primarily explore the various modeling approaches used by workers worldwide to better understand the behavior of such structures. The review focuses on the static and dynamic response of the structure due to various environmental conditions, such as wind, waves, and current. Emphasis is placed on modeling techniques and methods of solution. Many modeling and analysis techniques are common to the aerospace and ocean engineering communities due to the similarities in structural and environmental complexities. For example, aerodynamic loads on offshore platforms are a significant part of any analysis. Also, fluid loading models bear great similarities to mechanistic wind loading models. It is in this vein that a review paper with the focus offshore structures is included in a journal of aerospace engineering.