Showing papers on "Composite laminates published in 1973"
TL;DR: In this article, a sufficiently accurate analysis for statics and dynamics of composite laminates is presented, where the displacements are assumed piecewise linear across the thickness and the effects of transverse shear deformations and rotary inertia are included.
343 citations
TL;DR: In this article, a detailed design of a laminate specimen which can exhibit catastrophic delamination induced by interlaminar tension is presented, along with a preliminary failure hypothesis to characterize this mode of rupture and the associated experimental demonstration of the phenomena.
290 citations
TL;DR: In this paper, the results of an investigation which analytically relates the fiber/matrix nonlinearities to the post yielding behavior of symmetric laminates made from unidirectional plies are presented.
Abstract: This paper and a subsequent one will present the results of an investiga tion which analytically relates the fiber/matrix nonlinearities to the post- yielding behavior of symmetric laminates made from unidirectional plies. This first paper is primarily concerned with the behavior of the single ply and the means for anticipating its response within a laminate. Boron and carbon/epoxies are considered along with a metal matrix composite. The qualitative features of the response of these unidirectional materials to normal, shear, and combined loads are discussed. The analysis (based on triangular finite element idealizations of regularly-spaced inclusion arrays) anticipates the level of nonlinearity that has been observed in composite shear and transverse tensile tests. Also, it reveals a nonlinear coupling that may exist between the combined shear and normal stress response.
75 citations
48 citations
TL;DR: The use of these properties in the analysis of structural composites is outlined in this article, where typical results are presented for composite material properties, for laminate properties and for plate problems in which material stiffness is a significant design criterion.
20 citations
01 Jun 1973
TL;DR: In this paper, a finite element analysis program is used to examine elastic and plastic interlaminar shear at free edges in composite laminates, including graphite-epoxy and boron- epoxy with holes.
Abstract: : The results of an analytical and experimental program to investigate the behavior of advanced composite plates with cutouts are presented. Classi-cal and numerical analyses of anisotropic plates are compared with data from composite panels instrumented with strain gages, photoelastic coatings, and moire fringe multiplication techniques. A finite element analysis program is used to examine elastic and plastic interlaminar shear at free edges in composite laminates. The behavior of fiberglass-epoxy, graphite-epoxy, and boron- epoxy laminates with holes is examined for uniaxial and biaxial tension. The compressive behavior of graphite-epoxy and boron-epoxy laminates with holes is discussed. Test and analysis results for boron-epoxy laminates demonstrate the influence of such variables as fiber orientation, stacking sequence, load history, hole roughness, hole shape, diameter/width ratio, diameter/thickness ratio, loading rate, and hole reinforcement. Data and recommendations for design are discussed. (Author-PL)
13 citations
9 citations
9 citations
TL;DR: In this paper, the elastic response of a helical wound composite tube under pure bending was determined using an existing general solution for a wide class of boundary value problems, and theoretical results for several composite materials of engineering interest were presented which illustrate the influence of material properties on the stress field.
Abstract: In order to simulate the influence of specimen misalignment, we determine the elastic response of a helical wound composite tube under pure bending using an existing general solution for a wide class of boundary value problems. Theoretical results for several composite materials of engineering interest are presented which illustrate the influence of material properties on the stress field.
9 citations
TL;DR: In this article, a method is presented for estimating the stress intensity factor characteristic of crack extension in a specially orthotropic advanced fiber composite laminate, based on the elastic properties and ultimate principal strengths of a lamina, the laminate construction, and the experimentally determined value of the characteristic stress intensity factors of an arbitrary angle-plied, midplane symmetric laminate.
Abstract: A method is presented for estimating the stress intensity factor characteristic of crack extension in a specially orthotropic advanced fiber composite laminate, based on the elastic properties and ultimate principal strengths of a lamina, the laminate construction, and the experimentally determined value of the characteristic stress intensity factor of an arbitrary angle-plied, midplane symmetric laminate. A comparison of the results obtained from this method with limited experimental data for graphite/epoxy laminates indicates that the method is quite accurate for this particular material system. The predictive method is also used, in conjunction with experimental data, to estimate the size of a damage zone surrounding the crack tip.
8 citations
TL;DR: The applicability of linear elastic fracture mechanics (LEFM) to advanced fiber composite laminates is considered in this article, where a homogeneous material model is used to determine fracture toughness of graphite/epoxy Laminates.
Abstract: The extension of linear elastic fracture mechanics (LEFM) from metallic alloys to advanced fiber composite laminates is considered. LEFM is shown to be applicable to both isotropic and anisotropic homogeneous continua; the applicability of LEFM to advanced fiber composites is thus dependent on the validity of a homogeneous continuum model for such materials. An experimental program to determine the validity of such a model for graphite/epoxy laminates is reviewed. Such laminates are found to have an apparent fracture toughness, from which it is inferred that a homogeneous material model is appropriate for the particular specimen geometry and composite laminates considered. Strain energy release rates are calculated from the experimentally determined fracture toughnesses of the test laminates. These strain energy release rates fall into two distinct groups, corresponding to fracture across fibers and fracture between fibers. The latter case is further investigated. It is concluded that matrix fracture is governed by the tensile stress normal to the crack path.
Patent•
29 May 1973
TL;DR: In this article, pressure sensitive electrostatic imaging labels and label stock consisting of a laminate of an electrostatic face material, an adhesive layer and a release coated liner containing an electroconductive agent are provided.
Abstract: There is provided pressure-sensitive electrostatic imaging labels and label stock consisting of a laminate of an electrostatic imaging face material, an adhesive layer and a release coated liner containing an electroconductive agent. The composite laminates have electrical characteristics which permit excellent reproduction of images using photocopying systems conventional to the electrostatic imaging face material used.
TL;DR: In this paper, a fast accurate method for making crack measurements using moire fringes is proposed, which can be applied to stationary as well as running crack length measurement and to measurement of crack opening displacement.
Abstract: Where crack propagation governs failure of composite materials, understanding of fracture phenomena requires precise determination of running crack behavior. A fast accurate method is proposed for making crack measurements using moire fringes. The method can be applied to stationary as well as running crack length measurement and to measurement of crack opening displacement. Moire fnnges are the interference pattern resulting from the superposition of two gratings. They can be interpreted as contours of constant displacement components [ 1, 2]. If one grating is fixed to a specimen and a second used as a
01 Apr 1973
TL;DR: In this paper, an extension of linear elastic fracture mechanics from ostensibly homogeneous isotropic metallic alloys to heterogeneous anisotropic advanced fiber composites is considered, and it is analytically demonstrated that the effects of material anisotropy do not alter the principal characteristics exhibited by a crack in a material.
Abstract: The extension of linear elastic fracture mechanics from ostensibly homogeneous isotropic metallic alloys to heterogeneous anisotropic advanced fiber composites is considered. It is analytically demonstrated that the effects of material anisotropy do not alter the principal characteristics exhibited by a crack in an isotropic material. The heterogeneity of fiber composites is experimentally shown to have a negligible effect on the behavior of a sufficiently long crack. A method is proposed for predicting the fracture strengths of a large class of composite laminates; the values predicted by this method show good agreement with limited experimental data. The limits imposed by material heterogeneity are briefly discussed, and areas for further study are recommended.
01 Apr 1973
TL;DR: In this paper, an extension of linear elastic fracture mechanics from ostensibly homogeneous isotropic metallic alloys to heterogeneous anisotropic advanced fiber composites is considered, and it is analytically demonstrated that the effects of material anisotropy do not alter the principal characteristics exhibited by a crack in a material.
Abstract: The extension of linear elastic fracture mechanics from ostensibly homogeneous isotropic metallic alloys to heterogeneous anisotropic advanced fiber composites is considered. It is analytically demonstrated that the effects of material anisotropy do not alter the principal characteristics exhibited by a crack in an isotropic material. The heterogeneity of fiber composites is experimentally shown to have a negligible effect on the behavior of a sufficiently long crack. A method is proposed for predicting the fracture strengths of a large class of composite laminates; the values predicted by this method show good agreement with limited experimental data. The limits imposed by material heterogeneity are briefly discussed, and areas for further study are recommended.