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Philip H. Francis

Bio: Philip H. Francis is an academic researcher from Southwest Research Institute. The author has contributed to research in topics: Micromechanics & Crack growth resistance curve. The author has an hindex of 5, co-authored 16 publications receiving 235 citations.

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TL;DR: In this paper, the authors present a survey of the structural mechanics of composite materials, focusing on the macromechanical structural analysis of various structural elements, including response under conditions of stable static loading, buckling, and dynamics.
Abstract: Introduction T purpose of this Survey is to review and bring together in an orderly fashion some of the principal contributions to the field of structural mechanics of structures containing composite materials. The topics of micromechanics and fracture, while quite important, are not considered in this Survey. Emphasis is given to the macromechanical structural analysis of various structural elements, including response under conditions of stable static loading, buckling, and dynamics. The Survey unfolds in the following sequence: Straight and Curved Laminated Bars, Laminated Plates, Laminated Shells, Sandwich Structures, Applications to Practical Structural Systems, and Future Trends. The authors hope that this contribution will be a useful reference tool for researchers and engineers already involved in structural aspects of advanced composites, as well as for those who are just entering the field. No Survey can do full justice to such a wide field as compositematerial structural mechanics. The references cited give only a glimpse of the extensive literature in this field. The authors apologize for not citing a number of important contributions in the field.

115 citations

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TL;DR: In this paper, a theory was developed based on the Hill plane stress model which enabled the S-N curve for combined stress states to be predicted from the S N data for the uniaxial loading modes.
Abstract: Thin walled, 2.54-cm (1-in.) diameter tubular specimens of T300/934 graphite/epoxy were fabricated and fatigue cycled in combinations of axial, torsional, and internal pressure loading. Two different four-ply layup configurations were tested: (0/90)S and (+ or - 45)S; all tubes contained a 0.48-cm (3/16-in.) diameter circular hole penetrating one wall midway along the tube length. S-N curves were developed to characterize fatigue behavior under pure axial, torsional, or internal pressure loading, as well as combined loading fatigue. A theory was developed based on the Hill plane stress model which enabled the S-N curve for combined stress states to be predicted from the S-N data for the uniaxial loading modes. Correlation of the theory with the experimental data proved to be remarkably good.

56 citations

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TL;DR: In this article, the first-ply failure (FPF) envelopes were determined using a replication technique and compared with ultimate strength envelopes and lamination theory predictions of FPF using a maximum strain criterion and accounting for initial strains due to curing.

22 citations

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TL;DR: In this article, an experimental investigation was made of the surface deformation and extent of plastic yielding associated with relatively deep semielliptical surface cracks in plates subjected to tensile loading.

8 citations

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TL;DR: In this article, a simplified discrete theory developed by Hedgepeth is used to generate elastic solutions for stress concentration problems in filamentary materials containing flaws of arbitrary geometry, subjected to remote uniaxial tension.

8 citations


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Journal ArticleDOI
TL;DR: An extension of the Sanders shell theory for doubly curved shells to a shear deformation theory of laminated shells is presented in this paper, which accounts for transverse shear strains and rotation about the normal to the shell midsurface.
Abstract: An extension of the Sanders shell theory for doubly curved shells to a shear deformation theory of laminated shells is presented. The theory accounts for transverse shear strains and rotation about the normal to the shell midsurface. Exact solutions of the equations are presented for simply supported, doubly curved, cross‐ply laminated shells under sinusoidal, uniformly distributed, and concentrated point load at the center. Fundamental frequencies of cross‐ply laminated shells are also presented. The exact solutions presented herein for laminated composite shells should serve as bench mark solutions for future comparisons.

495 citations

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TL;DR: In this paper, a modeling technique for simulating the fatigue behavior of laminated composite materials, with or without stress concentrations, called progressive fatigue damage modeling, is presented. But this technique is not suitable for the case of composite materials.
Abstract: In this research a modeling technique for simulating the fatigue behaviour of laminated composite materials, with or without stress concentrations, called progressive fatigue damage modeling, is es...

353 citations

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TL;DR: A review of displacement and stress based refined theories for isotropic and anisotropic laminated plates is presented in this paper, together with their merits and demerits, where exact elasticity solutions for the plate problems are cited.
Abstract: A review of displacement and stress based refined theories for isotropic and anisotropic laminated plates is presented. Various equivalent single layer and layerwise theories for laminated plates are discussed together with their merits and demerits. Exact elasticity solutions for the plate problems are cited, wherever available. Various critical issues related to plate theories are presented, based on the literature reviewed.

342 citations

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TL;DR: In this paper, a new concept called fatigue modulus, defined as a slope of applied stress and resultant strain at a specific cycle is introduced, which is used to predict the fatigue life of glass fiber reinforced epoxy composite materials better than S-N curve or Basquin's relation.
Abstract: Fatigue behavior of glass fiber reinforced epoxy composite materials has been studied analytically. A new concept called "fatigue modulus," which is defined as a slope of applied stress and resultant strain at a specific cycle is introduced. Fatigue modulus degradation is studied using an assumption that the fatigue modulus degrada tion rate follows a power function of fatigue cycle. Theoretical equation for predicting fatigue life is formulated using the fatigue modulus and its degradation rate. This rela tion is simplified by strain failure criterion for the practical application. It is proved that the final formula predicts the fatigue life of a glass fiber epoxy composite material better than S-N curve or Basquin's relation. An attempt is made to find the relation ship between fatigue modulus and elastic modulus by the geometric relation from stress-strain curve under the cyclic loading.

319 citations

Journal ArticleDOI
TL;DR: In this article, the uniaxial tensile load at which transverse cracking initiated in the 90 deg. laminates was determined experimentally using DIB enhanced x-radiography.
Abstract: The uniaxial tensile load at which transverse cracking initiated in the 90 deg. laminae of (0 2/90n)s, (±30/90n) s and (±60/90n)s, n =1,2,4,8, T300/934 composite laminates was determined experimentally using DIB enhanced x-radiography. "In situ" transverse strengths of the 90 deg. laminae corresponding to these loads were then calculated based upon lamination theory predictions including the effects of residual thermal stresses. These in situ strengths, which were as high as 2.5 times the unidirec tional transverse strength, were found to depend strongly on both the 90 deg. laminae thickness and orientation of adjacent laminae suggesting that transverse strength should not be considered as an intrinsic lamina property.

317 citations