Fiber Reinforced Polymer Composite Shell Research Articles

Wave dispersion characteristics of laminated carbon fiber reinforced polymer composite shells resting on viscoelastic foundations under thermal field

Wave dispersion characteristics of laminated composite shells resting on viscoelastic foundations in thermal environments are examined. Three types of temperature distributions (i.e., uniform, linear, and sinusoidal) along the thickness of the laminates are considered. Effective material properties of the carbon fiber reinforced polymer (CFRP) composite are calculated by the Mori-Tanaka homogenization method. The four-variable higher-order shear deformation theory (HSDT) and Hamilton principle are utilized to derive the equations of motion. The Navier approach in conjunction with wave solution is exploited to obtain the dispersion relations of the simply supported laminated shells with cross-ply and antisymmetric angle-ply arrangements. A comparative study is performed to demonstrate the validity of the present model. A parametric study is conducted with focus on the effects of curvature ratio, viscoelastic foundation parameters, carbon fiber volume fraction, number of layers, lamination scheme, temperature distribution, temperature difference, and fiber orientation on the wave dispersion behavior. Numerical results manifest that uniform temperature distribution reduces the phase velocity furthest. At low wave number, the extrema of phase velocity are determined by the curvature ratio and fiber orientation. The results can be used for the ultrasound detection techniques and structural health monitoring.

Instability-driven shape forming of fiber reinforced polymer frames

Thin fiber reinforced polymer (FRP) composites are widely implemented in adaptive and morphing structures. However, realization of the necessary complex 3-dimensional FRP structures requires the use of expensive molds thereby limiting the design space and flexibility. Using the elastic strain energy of pre-stretched membranes holds potential for addressing this challenge. In this work, a novel manufacturing technique for fabricating 3-dimensional FRP structures moldlessly is presented where pre-stretched membranes are used to drive out-of-plane buckling instabilities of FRP composite shells. To explore the potential of this approach, a simple square frame design is investigated. An analytical model based on high deformation beam buckling theory is developed for understanding the parameters driving the out-of-plane behavior of these structures. Experimental and finite element results are used for model validation and reveal excellent agreement, with errors less than 10% over a large portion of the design space. Analytical and finite element models demonstrate that the out-of-plane deformation can be tailored by varying the structure’s geometric and material parameters. A new design space for FRP composite laminates is characterized, enabling highly flexible design. The manufacturing and modeling techniques can be extended to other geometries for the realization and analysis of arbitrarily complex surfaces.

Durability assessment of hybrid FRP composite shell and its application to prestressed concrete girders

This paper presents the results of an experimental-analytical research program aimed at assessing the durability of a hybrid fiber-reinforced polymer (FRP) composite shell, incorporated as a protective barrier during construction to impede the ingress of deleterious elements into the lower flange of a prestressed concrete girder. A series of tests were performed on the FRP composite shell and FRP-concrete specimens to examine the effectiveness of the FRP shell as a barrier against ingress of aggressive elements, such as moisture and chlorides in controlled environments. In addition, scanning electron microscopy (SEM) was used to determine the effects of aging, temperature variation and chloride diffusion in the FRP-concrete specimens. These experimental results were used to model the ingress of chlorides and moisture into the FRP-concrete system to predict the service life of prestressed concrete bridge girders reinforced with FRP composite shells. The results showed that the FRP composite shell can provide significant resistance against chloride ingress by impeding the rate of its ingress and the total amount of chloride ions, thus considerably help in retarding the resulting deterioration reactions and significantly enhancing their service life.

Optimal Actuators Locations in Smart Fibre Reinforced Polymer Structures Using Genetic Algorithm

The present paper describes the development of a genetic algorithm (GA) based methodology for determination of optimal number of actuators and their locations in smart fiber reinforced polymer composite shell structures. Finite element (FE) based state space representation of the system has been used to determine the optimal placement of actuators in order to maximize the controllability. Spillover from residual modes has also been considered while maximizing controllability. Even though the developed methodology needs a large computational time, it will be useful in off-line determination of optimal actuators locations in large structures.

Repair of Wood Piles Using Prefabricated Fiber-Reinforced Polymer Composite Shells

An effective method for combined environmental protection and structural restoration of wood piles in waterfront facilities is not available. The objective of the study presented in this paper is to survey the available methods for wood pile protection and structural restoration with the intent of developing an effective method. In addition to reviewing the available repair methods, a field inspection of a harbor in Maine was conducted to assess existing technologies. A wood pile repair method that utilizes bonded fiber-reinforced polymer (FRP) composite shells and a grouting material is proposed. Fiber, resin, adhesive, coating, and grouting materials are systematically analyzed to deliver the required system performance. Two fabrication methods for the FRP composite shells are discussed based on the experience gained in the fabrication of laboratory prototypes. Then a step-by-step procedure amenable for field installation is proposed, and a preliminary cost analysis is conducted to assess the feasibility of the proposed system.

Fiber Reinforced Polymer Composite–Wood Pile Interface Characterization by Push-Out Tests

Structural restoration of spliced or damaged wood piles with fiber reinforced polymer (FRP) composite shells requires that shear forces be transferred between the wood core and the encasing composite shells. When a repaired wood pile is loaded, shear stresses develop between the wood pile and the FRP composite shell through the grouting material. Alternatively, shear force transfer can be developed through mechanical connectors. The objective of this study was to characterize the interfaces in wood piles repaired with FRP composite shells and grout materials. Two interfaces were studied: wood pile/grout material and a grout material/innermost FRP composite shell. A set of design parameters that control the response of both interfaces was identified: (1) extent of reduction of cross section of wood pile due to deterioration (necking); (2) type of grout material (cement-based or polyurethane); (3) use of mechanical connectors; and (4) addition of frictional coating on the innermost shell. Push-out tests by compression loading were performed to characterize the interfaces and discriminate the effect of the design parameters. The outcome of the push-out tests was evaluation of the shear stress and force versus slip response and characterization of the failure mechanism. A set of repair systems that represent different combinations of the design parameters was fabricated and the interfaces evaluated. It was found that the combination of cement-based grout and polymer concrete overlay on the innermost shell provided the most efficient shear force-slip response. A simplified piecewise linear model of shear stress versus slip at the wood/grout and grout/FRP composite interfaces with and without mechanical connectors is proposed to synthesize the experimental response.