A history of the losipescu shear test as applied to composite materials is presented along with a description of the test fixture and specimen design. Iosipescu's shear test is compared to similar test techniques, including the asymmetrical four-point bending (AFPB) test. Finally, in-plane and through-the-thickness shear properties measured using the losipescu shear tests are presented for a variety of materials, including a unidirectional graphite/epoxy, random and continuous-fiber sheet molding compounds, and two polymer materials.

The losipescu shear test as applied to composite materials

During the past several years, considerable study of the Iosipescu shear test method has been conducted by a number of investigators, including the present authors. Several different test fixture designs have been developed, and variations of the specimen size and notch configuration have been considered. Materials with properties ranging from isotropic to highly orthotropic have been tested. The response of such materials has also been predicted using finite element techniques, and attempts have been made to correlate these predictions with available experimental data. This recent work is summarized here, with particular emphasis being given to the correlations and contradictions resulting from the published works of these various investigators.

Current status of the Iosipescu shear test method

The stress state in the bonded joint region of a laminated composite tube subjected to torsional and hygrothermal loadings is analyzed. A finite ele ment solution technique is utilized. The composi...

Analysis of a Bonded Joint in a Composite Tube Subjected to Torsion

Multiscale modeling of mechanical behaviors of carbon fiber reinforced epoxy composites subjected to hygrothermal aging

High precision composite pipes for SOLAR-B optical structures

The influence of variations in fiber and matrix constituent material properties on the moisture and thermal expansion coefficients of a unidirectional composite is demonstrated, using a finite element, inelastic micromechanics analysis. Three of the commonly utilized graphite/epoxy material systems are selected for detailed analysis, using available experimental values of the constituent material properties wherever possible. The epoxy matrix is assumed to be Hercules 3501-6 in all cases, a polymer which is fully representative of the various structural epoxies in current use. The three graphite fibers are Celanese GY-70, Hercules HMS, and Hercules AS, representative of high, medium, and low modulus graphite fibers, respectively.

Moisture Expansion and Thermal Expansion Coefficients of a Polymer-Matrix Composite Material

: A three-dimensional elastoplastic analysis of generally orthotropic composite laminates is developed, together with a finite element computer code NCLAP (nonlinear Composite Laminate Analysis Program) for its implementation. The analysis is capable of handling any laminated composite subjected to triaxial mechanical and/or hygrothermal loading conditions. The laminates can consist of any number of orthotropic material piles, of any orientations. Elastoplastic material behavior is included by means of the tangent modulus method. The onset of plastic deformation is determined by a failure surface in three-dimensional space, and is likewise dependent on temperature and moisture. The three-dimensional finite element analysis is based on a displacement formulation employing linear isoparametric elements. Large aspect ratios, typical of laminae finite element representations, are handled by the use of reduced integration techniques. Material properties are input to NCLAP as coefficients of second order polynomials describing the elastoplastic response, and the dependence on temperature and moisture content. Incremental mechanical loadings can be applied as nodal forces and/or prescribed displacements. Hygrothermal loadings are applied as constant overall changes, or as spatial distributions, of temperature and moisture content. Computer Program NCLAP has been developed in modular form, which will permit it to be easily modified to accommodate future extensions of the analysis. (Author)

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Mohamed M. Monib

Papers

Moisture Expansion and Thermal Expansion Coefficients of a Polymer-Matrix Composite Material

Three-Dimensional Elastoplastic Finite Element Analysis of Laminated Composites.