Showing papers in "Journal of Reinforced Plastics and Composites in 1983"
TL;DR: In this paper, a double cantilever beam test is used to measure GIC values in angle ply composites and it is demonstrated that the GIC value determined with this method are independent of the compliance of the spec.
Abstract: A double cantilever beam test is used to measure GIC values in angle ply composites. It is demonstrated that the GIC values determined with this method are independent of the compliance of the spec...
101 citations
TL;DR: In this article, experimental techniques were presented for determining the moisture and thermal expansion coefficients of polymers and polymer-matrix composite materials, including Hercules 3501-6 and polypropylene polysilicon composite materials.
Abstract: Experimental techniques are presented for determining the moisture- and thermal- expansion coefficients of polymers and polymer-matrix composite materials. Materials tested included Hercules 3501-6...
45 citations
TL;DR: In this paper, a brief description of the Fickian diffusion behavior in polymer composites, containing impermeable fibres (glass and graphite) is presented, and the applicability of such a model to composites based on a permeable fibre phase (jute) is verified, both under the influence of varied internal (fibre volume fraction) and external (ambient temperature) factors.
Abstract: A brief description of the Fickian diffusion behavior in polymer composites, containing impermeable fibres (glass and graphite) is presented. The applicability of such a model to composites based on a permeable fibre phase (jute) is verified, both under the influence of varied internal (fibre volume fraction) and external (ambient temperature) factors. Very good correlations are found between the experimental data and a modified Fickian diffusion plot. The significance of a resin impregnated fibre volume fraction in such a composite is highlighted.
36 citations
TL;DR: In this paper, failure envelopes for all these failure criteria are drawn for (0/90/±45)s laminate made of T300/5208 graphite epoxy material in stress space.
Abstract: On the basis of a recent survey conducted by AIAA composite structures subcom mittee, the failure criteria used by more than ninety percent design engineers have been considered in this study. These failure criteria are maximum stress, maximum strain and quadratic polynomial (Tsai Wu, Chamis, Hoffman and Hill) failure criteria. Failure envelopes for all these failure criteria are drawn for (0/90/±45)s laminate made of T300/5208 graphite epoxy material in stress space. For the first ply failure strength, we observe a great deal of difference in the predictions made by these failure criteria. Depending upon the failure criteria being compared, the maximum percentage dif ference ranges to 75%. Because of the criticality of failure criteria in structural design, for a better confidence in the predicted strength, it is necessary to undertake further theoretical and experimental studies in failure criteria. Computer aided optimum designs may not be optimum if the correct failure criteria is not considered.
34 citations
TL;DR: In this paper, the behavior of eight-ply, quasi-isotropic, graphite epoxy laminates subjected to low velocity transverse impact loading was discussed and large deflection theory of plates was used to predict the load-deflection characteristics during the impact event.
Abstract: This work discusses the behavior of eight-ply, quasi-isotropic, graphite epoxy laminates subjected to low velocity transverse impact loading Large deflection theory of plates was used to predict the load-deflection characteristics during the impact event The impact model considered that the indentation, flexural and shear stiffnesses could be represented by three-equivalent springs in series The analysis of static and dynamic impact loading test-data concluded that the membrane parameter, beta, used in flexural stiffness relation was proportional to the square of the coefficient of restitution, e, of the impactor Use of beta=0443 e-squared was made in load-deflection relations to consider the drop in plate stiffness due to delamination The results of impact tests up to impact velocity 53 m/sec were found in close agreement with the predictions
33 citations
TL;DR: In this paper, an energy dissipation model was developed to predict the residual strength of graphite-epoxy T300/5208 composite laminates from impact damage by a cantilever-type instrumented 1-inch diameter steel ball.
Abstract: This report contains the study of Low Velocity Transverse Impact Damage of graphite-epoxy T300/5208 composite laminates. The specimen, 100 mm diameter clamped plates, were impact damaged by a cantilever-type instrumented 1-inch diameter steel ball. Study was limited to impact velocity 6 m/sec. Rectangular strips, 50 mm x 125 mm, were cut from the impact-damage specimens so that the impact damage zone was in the center of the strips. These strips were tested in tension to obtain their residual strength. An energy dissipation model was developed to predict the residual strength from fracture mechanics concepts. Net energy absorbed I(a) was evaluated from coefficient of restitution concepts based on shear dominated theory of fiber-reinforced materials, with the modification that during loading and unloading the shear deformation are respectively elastic-plastic and elastic. Delamination energy I(d) was predicted by assuming that the stiffness of the laminate dropped due to debonding. Fiber-breakage energy, assumed to be equal to the difference of I(a) and I(d), was used to determine the residual strength. Predictions were compared with test results.
33 citations
TL;DR: In this paper, the strength and variability of carbon and glass fibers have been estimated in several ways from tests on single fibers and loose bundles of fibers, which involved analyzing the variation of strength with the length of the fibers, the distribution of strengths, multiple fractures of a single fiber, and shape of the stress/strain curve for a loose bundle.
Abstract: The strength and variability of carbon and glass fibers have been estimated in several ways from tests on single fibers and loose bundles of fibers. These tests involved analyzing the variation of strength with the length of the fibers, the distribution of strengths, multiple fractures of a single fiber, and the shape of the stress/strain curve for a loose bundle. The procedures based on loose bundle tests are considerably easier to perform and provide very similar results. Tows of the same batches of fibers were impregnated with epoxy resin and the tensile strengths of the resulting composites were found to be approximately 2.5 times higher than those of the equivalent loose bundles. A rule-of-mixtures approach is unable to account for this ratio, but two- and three- dimensional probabilistic models provide good predictions of the relative strengths.
31 citations
TL;DR: In this paper, the optical method of caustics and the T-criterion of fracture were applied to in vestigate and explain the process of interface disruption, which takes place when a moving transverse crack reaches and coalesces with a weak longitudinal interface of a bi-phase plane specimen.
Abstract: The optical method of caustics and the T-criterion of fracture were applied to in vestigate and explain the process of interface disruption, which takes place when a moving transverse crack reaches and coalesces with a weak longitudinal interface of a bi-phase plane specimen. A quantitative criterion was then established, based on the T-criterion, which relates the mechanical properties of the interface with the mechanical properties of subsequent phase of penetration of the crack for the critical condition of crack propagation either along the interface, or along the second phase.
17 citations
TL;DR: In this article, the authors proposed a new D criterion theory which includes a new physical quantity, the damage parameter, D, a new material property, the ultimate damage, Dc, and a new criterion, D ≤ Dc.
Abstract: This paper proposes a new D criterion theory which includes a new physical quantity —the damage parameter, D, a new material property—the ultimate damage, Dc and a new criterion—D ≤ Dc A number of experimental data are used to verify that the damage parameter, D, describes the degree of the damage near the notch after a certain applied load and that the ultimate damage, Dc, is a material constant independent of configuration of the specimen and the applied load
16 citations
TL;DR: In this article, the effects of moisture and temperature on the properties of chopped fiber reinforced sheet molding compounds were surveyed, including tensile strength and modulus, compression strength, shear strength, flexural strength, fatigue, creep and vibration damping.
Abstract: A summary is given on the effects of moisture and temperature on the properties of chopped fiber reinforced sheet molding compounds. The properties surveyed include tensile strength and modulus, compression strength and modulus, shear strength and modulus, flexural strength and modulus, fatigue, creep, vibration damping, moisture absorption characteristics, and thermal expansion.
14 citations
TL;DR: In this paper, the authors present simple techniques to design unstiffened, strength-controlled composite panels while exploiting the high unidirectional strength composites offer, including provisions for the design of panels where the loads are not constant across the length and width of the panel.
Abstract: This paper presents simple techniques to design unstiffened, strength-controlled composite panels while exploiting the high unidirectional strength composites offer. Ply orientations are rotated until the best orientations are found to produce the lightest weight structure. Strength is then aligned to where, and only where, it is necessary. The techniques presented include provisions for the design of panels where the loads are not constant across the length and width of the panel. An important additional con sideration is the selection of ply stacking under multiple loading conditions. In an ex ample panel design, the techniques result in a 13% weight reduction over conventional [0i/90 j/±45k]s laminates.
TL;DR: In this article, simple rules for the versatile application of anisotropic, though orthotropic bidirectional laminates are presented, and simple examples and charts demonstrate the possible weight advantages over quasi-isotropic configurations.
Abstract: The intention of this report is to help develop a feeling for the directional properties of laminated composites. Simple rules for the versatile application of anisotropic, though orthotropic bidirectional laminates are presented. Simple examples and charts demonstrate the possible weight advantages over quasi-isotropic configurations. Ex plicit use is made of the Mohr's circle representation. Multiple loading is considered and a graphic solution is indicated.
TL;DR: In this article, the authors dealt with stresses around quasi-rectangular holes with minimum stress concentration in large orthotropic plates and presented numerical results in terms of quasirectangular hole shapes with minimal stress concentration and stress distribution around these holes.
Abstract: This paper deals with stresses around quasi-rectangular holes with minimum stress concentration in large orthotropic plates. The method given by Lekhnitskii is used. Numerical results are presented in terms of quasi-rectangular hole shapes with minimum stress concentration and stress distribution around these holes. Unidirec tional carbon/epoxy orthotropic composite materials are considered for a range of hole shapes under uniaxial and biaxial loading conditions.
TL;DR: In this article, a simplified model and method for finding the deflection char acteristics of stacked cardboard boxes, provided the load-deflection characteristic of the box is known, is presented.
Abstract: This paper presents a simplified model and method for finding the deflection char acteristics of stacked cardboard boxes, provided the load-deflection characteristic of the box is known. A computer program, based on this model, allows the stability of stacked boxes to be investigated and to indicate the limits to the height of the stack and box parameters required to prevent stack toppling.
TL;DR: In this article, Park et al. considered a similar problem extending the failure criterion to the Von Mises failure criterion, in which an optimal ply orientation angle was computed for various multiple loadings (N, N2, N6) under the first ply failure criterion.
Abstract: N THE PROBLEMS OF OPTIMAL LAMINATE DESIGN, IT IS WELL UNDERSTOOD th4t the most important design variables are ply orientation angles, ply thicknesses and volume fractions of fibers. Park [1] has considered an optimal laminate design problem, in which an optimal ply orientation angle was computed for various multiple loadings (N,, N2, N6) under the first ply failure criterion. This paper considers a similar problem extending the failure criterion to the Von Mises failure criterion. Various simple symmetric laminates of the composite material T300/5208, such as
TL;DR: In this article, the structural use of aramid composites is examined by an experimental analysis of mechanical joints in various types of laminates and the relationship between bearing strength and laminate type and thickness is investigated and the influence of the pitch/ diameter ratio is studied.
Abstract: Mechanical joints of carbon fibre composite materials has been the subject of exten sive research in the past decade. Theoretical as well as experimental studies are avail able. In this article the structural use of aramid is examined by an experimental analysis of mechanical joints in various types of laminates. The relationship between bearing strength and laminate type and thickness is investigated and the influence of the pitch/ diameter ratio is studied. The safe failure behaviour typical of aramid composites is demonstrated by testing riveted joints.
TL;DR: In this paper, the tensile behavior of laminates consisting of layers of veil, mat and woven roving is investigated and it is shown that the fracture strain of the laminate is always smaller than the fracture force of the more brittle constituent layer.
Abstract: The tensile behavior of laminates consisting of layers of veil, mat and woven roving is investigated. The results show that the fracture strain of the laminate is always smaller than the fracture strain of the more brittle constituent layer. It is shown that the rule of mixture can be used to calculate the modulus of the laminate knowing the moduli of the individual layers. The rule of mixture can also be used to calculate the tensile strength provided that the stress in the more ductile layer corresponding to the fracture strain of the more brittle layer is used.
TL;DR: In this paper, the authors describe the use of Radio Shack TRS-80 Pocket Computer for the key calculations of stiffness and strength of metric composite laminates, using the same formulas and equation numbers used in Tsai and Hahn's "Introduction to Composite Materials" (Technomic, 1980).
Abstract: This paper contains the descriptions and instructions of the use of Radio Shack TRS-80 Pocket Computer for the key calculations of stiffness and strength of sym metric composite laminates.Specific programs are constructed, using BASIC language, to give instant computa tions on:(1) In-Plane Stiffness of Symmetric Laminates(2) Flexural Rigidity of Symmetric Sandwich Plates(3) In-Plane Strength of Symmetric Laminates(4) Flexural Strength of Symmetric Sandwich PlatesThe formulas and equation numbers used in the programming are the same as that found in Tsai and Hahn's "Introduction to Composite Materials" (Technomic, 1980). Listings of the programs are included along with flow diagrams, operation charts and memory contents.It would be a simple matter to run the program on a variety of minicomputer systems by altering the syntax as appropriate.
TL;DR: The paper of Lindeman, Witemberg-Perzyk and Perzyk claiming that Goodier's solution for the stress concentration around a spherical inclusion under tension is in correct is criticized as mentioned in this paper.
Abstract: The paper of Lindeman, Witemberg-Perzyk and Perzyk claiming that Goodier's solution for the stress concentration around a spherical inclusion under tension is in correct is criticized. It is concluded that Goodier's solution is still correct.
TL;DR: In this article, a study was made of the theoretical analysis, strength and fracture of the ferritic phase in dual phase steels, in which the martensitic phase has encapsulted islands.
Abstract: A study was made of the theoretical analysis, strength and fracture of the ferritic phase in dual phase steels, in which the martensitic phase has encapsulted islands. The importance of a knowledge of micro-cleavages of ferrite grains under a monotonic loading test has been assessed, not only in the study of the influence of plastic con straint but also in the theoretical analysis of the occurence of cleavage cracking on fer rite grains by plastic constraint.
TL;DR: In this paper, the authors demonstrate the possible effect of couple stresses on the transverse elastic moduli of anisotropic composite material systems and derive a numerical solution for the transversal elastic stiffness of the composite material as a function of the elastic constants, including the modulus of curvature, of the fiber and the matr...
Abstract: The purpose of this paper is to demonstrate the possible effect of couple stresses on the transverse elastic moduli of anisotropic composite material systems. Couple stress theory considers that within an elastic body, the surface of each element of material is subjected not only to normal and tangential stress components but also to a moment component designated as a couple stress, thus introducing another elastic constant of the material.The necessary theory of elasticity needed for this purpose is developed and extended from the available classical theory found in the literature. The model considered is a uniaxially loaded infinitely long rectangular cell of composite material with a circular fiber located at the center. The stress and displacement fields thus developed in the composite cell are for the plane strain case.A numerical solution for the transverse elastic stiffness of the composite material as a function of the elastic constants, including the moduli of curvature, of the fiber and the matr...
TL;DR: In this paper, the nonlinear energy method for mixed mode fracture has been applied to analyze the off-axis cracked lamina of composite material subjected to biaxial loading, and several examples have been given to explain the influence of fiber-orientation, bao-ial loading factor and how the non-linear correction factors vary with changes of the applied load.
Abstract: The general G-K relation has been obtained and the nonlinear energy method generalized to analyzing the mixed mode fracture problem by W. Shen and James D. Lee. For the special case in which the line crack is perpendicular to one of the major loading axes, it has been found that the linear energy release rate is independent of the biaxial load factor while the nonlinear energy rate depends on it. In this paper, based on the nonlinear energy method for mixed mode fracture, the calculations for the pro cess of the nonlinear rate of off-axis cracked lamina of composite material subjected to biaxial loading have been performed. In addition, several examples have been given to explain the influence of fiber-orientation, biaxial loading factor and how the nonlinear correction factors vary with changes of the applied load.
TL;DR: In this paper, it is shown that the Zhurkov method for testing the strength of solids can be applied to dynamic tension and to cyclic loading and provides a viable approach to accelerated testing of composites.
Abstract: It is shown that the Zhurkov method for testing the strength of solids can be applied to dynamic tension and to cyclic loading and provides a viable approach to accelerated testing of composites. Data from the literature are used to demonstrate a straightforward application of the method to dynamic tension of glass fiber and cyclic loading for glass/polymer, metal matrix, and graphite/epoxy composites. Zhurkov's equation can be used at relatively high loads to obtain failure times at any temperature of interest. By taking a few data points at one or two other temperatures the spectrum of failure times can be expanded to temperatures not easily accessible.
TL;DR: In this article, a theoretical model is formulated to describe solid state eutectoid transformation, and solutions incorporating appropriate boundary conditions are derived for transient and steady states for both the transient and the steady states.
Abstract: A theoretical model is formulated to describe solid state eutectoid transformation. Solutions incorporating appropriate boundary conditions are derived for transient and steady states. It is shown that the transient solution describes build up of the interfacial boundary layer, whereas the steady state solution extends into the phase. The presence of this boundary layer with considerable concentration and temperature gradients sug gests a solid state analogue to constitutional super cooling, as in the liquid to solid transformation.