Advanced Materials and Structures: Analysis Methods and Results

Advanced and innovative materials are used increasingly in civil and aerospace engineering. To meet the demands of advanced materials in structural applications, novel analytical and experimental techniques have been developed to simulate and characterize the material responses and structural behaviors. To this end, this special issue of the Journal of Aerospace Engineering aims to present a collection of invited papers concerning the analytical and experimental techniques for advanced and emerging materials and structures in civil and aerospace engineering.

The papers selected for this issue are primarily based on the presentations delivered in the three “Advanced Materials in Structures” sessions organized by the ASCE Aerospace Division’s Committee on Advanced Materials and Structures at the 44th AIAA/ASME/ASCE/AHS/ACS Structures, Structural Dynamics, and Materials (SDM) Conference, Norfolk, Va., April 7–10, 2003. Seven papers based on the presentations have been peer reviewed and are included in this special issue. Among them, a wide range of analytical and experimental techniques are covered, ranging from constitutive modeling, to advanced numerical simulation, and to novel experimental characterization of composite materials and novel structural systems. The papers address critical issues in the rapidly growing fields of civil/aerospace materials and structures, including application of advanced materials (e.g., braided composites and coating materials), novel structures (e.g., sinusoidal core configuration and z-pin reinforcement), advanced experimental methods (e.g., ballistic impact tests), as well as analytical/numerical techniques (e.g., the nonlinear, strain rate-dependent constitutive models and linear time-dependent acoustic wave propagation) in support of test methods and applications. In most papers, a balanced approach of analytical, numerical, and experimental correlations is adopted, and their advancement to the state of the art in advanced materials and structures is illustrated.

In “Ballistic Impact of Braided Composites with a Soft Projectile,” Roberts et al. experimentally investigate the impact behaviors of aluminum plates, braided composite plates, and braided composite half-rings subjected to a soft gelatin projectile. The failure modes are identified, and an estimate of the penetration threshold is provided, which is useful for damage-tolerance evaluation of aerospace components (i.e., fan cases in commercial jet engines) under impact of high-strain energy density.

Ivancic and Palazotto’s “Experimental Considerations for Determining the Damping Coefficients of Hard Coatings” characterizes the dynamic behavior of a titanium plate coated with magnesium aluminate spinel, representing a turbine compressor blade. Various experimental tests using dynamic ping and laser vibrometry were performed to ensure the accurate measurement of vibration characteristics, which is important to represent the basic damping properties of a coating.

In “Implementation of an Associative Flow Rule Including Hydrostatic Stress Effects into High Strain Rate Deformation Analysis of Polymer-Matrix Composites,” Goldberg et al. present a constitutive law of nonlinear, strain rate dependent polymeric materials, which is primarily modified from the state variable constitutive equations originally developed for metals. They then implement the polymer constitutive equations to predict the nonlinear, strain rate dependent deformation of polymer matrix composites and compare the computed values with experimental data. The experimentally validated analytical constitutive laws are useful in explicit finite element analyses, and they provide a more realistic analysis of deformation during impact events for composite materials.

Butler et al. model the deformation fields of the reusable launch vehicle (RLV) thrust cell liner using the cylindrical version of the higher-order theory for functionally graded materials in conjunction with two inelastic constitutive models (i.e., Robinson’s unified viscoplasticity theory and the power-law creep model) in the paper “Role of the Material Constitutive Model in Simulating the RLV Thrust Cell Liner Response.” The creep/relaxation/temperature-driven “dog-house” failure mode is identified using the power-law model, and their study provides an insight to failure mechanism of RLV thrust cell liner.

Qiao and Wang’s “Mechanics of Composite Sinusoidal Honeycomb Cores” details a mechanics of material approach to evaluate the effective stiffness properties of a unique sinusoidal composite core currently being used in FRP sandwich bridge deck panels. Both the finite element unit cell modeling and experimental testing are carried out to validate the accuracy of the analytical formulation, and the analytical approach as an efficient tool in optimal design and sizing of sinusoidal cores are demonstrated.

Birman and Byrd’s paper is entitled “Effect of Z-Pins on Fracture in Composite Cocured Double Cantilever Beams.” The writers present a new analytical approach to evaluate the effect of z-pins on the strain energy release rate of composite double cantilever beams. A separate analysis of the intact and delaminated parts of DCB is proposed, and both the effect of z-pins using an elastic foundation and the rotational stiffness of the intact part by the Rayleight-Ritz solution are considered in the analysis of the compliance, compliance rate change, and strain energy release rate of the DCB specimen. The beneficial effect of z-pins on the delamination resistance of DCB is illustrated.

Finally, Hariharan and Sawyer’s paper “Transform Potential—Theoretic Method for Acoustic Radiation” furthers the development of a computationally efficient and accurate time domain computational model to determine the far field acoustic radiation. The transform potential theoretic (TPT) method is used to solve the linear time-dependent wave propagation problems in an unbounded medium. Case studies of acoustic wave propagation from a 2D bounded surface embedded in a uniform flow demonstrate the validity of the proposed robust procedure.

Many thanks to the writers who presented and shared their research findings in this special issue. We also appreciate the reviewers whose time and effort contributed to the high quality of the presented papers.