Estimate of compressive strength of an unidirectional composite lamina using cross-ply and angle-ply laminates

In this work has been estimated the compressive strength of a unidirectional lamina of a carbon/epoxy composite material, using the cross-ply and angle-ply laminates. Over the years various methods have been developed to deduce compressive properties of composite materials reinforced with long fibres. Each of these methods is characterized by a specific way of applying load to the specimen. The method chosen to perform the compression tests is the Wyoming Combined Loading Compression (CLC) Test Method, described in ASTM D 6641 / D 6641M-09. This method presents many advantages, especially: the load application on the specimen (end load combined with shear load), the reproducibility of measurements and the experimental equipment quite simplified. Six different laminates were tested in compressive tests. They were realized by the same unidirectional prepreg, but with different stacking sequences: two cross-ply [0/90]ns, two angle-ply [0/90/±45]ns and two unidirectional laminates [0]ns and [90]ns. The estimate of the compressive strength of the unidirectional laminates at 0°, was done by an indirect analytical method, developed from the classical lamination theory, and which uses a multiplicative parameter known as Back-out Factor (BF). The BF is determined by using the experimental values obtained from compression tests. Finally, extrapolated data were compared with prepreg manufacturer datashee

Estimate of compressive strength of an unidirectional composite lamina using cross-ply and angle-ply laminates

In this work has been estimated the compressive strength of a unidirectional lamina of a carbon/epoxy composite material, using the cross-ply and angle-ply laminates. Over the years various methods have been developed to deduce compressive properties of composite materials reinforced with long fibres. Each of these methods is characterized by a specific way of applying load to the specimen.The method chosen to perform the compression tests is the Wyoming Combined Loading Compression (CLC) Test Method, described in ASTM D 6641 / D 6641M-09. This method presents many advantages, especially: the load application on the specimen (end load combined with shear load), the reproducibility of measurementsand the experimental equipment quite simplified. Six different laminates were tested in compressive tests. They were realized by the same unidirectional prepreg, but with different stacking sequences: two cross-ply [0/90]ns, two angle-ply [0/90/±45]ns and two unidirectional laminates [0]ns and [90]ns.The estimate of the compressive strength of the unidirectional laminates at 0°, was done by an indirect analytical method, developed from the classical lamination theory, and which uses a multiplicative parameterknown as Back-out Factor (BF). The BF is determined by using the experimental values obtained from compression tests

Giant two-way shape memory effect in high-temperature Ni–Mn–Ga single crystal

AbstractA perfect two-way shape memory effect (TWSME) with reversible strain of about 9% has been found in the high-temperature Ni57.5Mn22.5Ga20.0 single crystal transforming into 2M non-modulated martensitic phase. Two thermal/mechanical treatment routes were utilized in the experimental procedures. The outstanding high-temperature TWSME is observed as a result of tensile stress-strain cycling along 〈100〉 axis involving huge superelastic strains due to stress-induced martensitic transformation. It is argued that the TWSME is related to the anisotropic internal stresses produced by a network of lattice defects. The defects are generated in the course of oriented growth/shrinkage of the dominating martensitic variant in the tensile sample

Temperature dependence of magnetically induced strain in single crystal samples of Ni–Mn–Ga

We investigate the effect of temperature and applied magnetic field on the strain behavior of oriented single crystal samples of Ni2MnGa. It is shown that the martensite twins can be partially oriented by the application of a magnetic field during cooling from the austenite state, observing a strain of the order of 1%. Depending on the final cooling temperature, a different value of magnetically induced strain is observed in the martensite phase, an effect due to the irreversible alignment of a fraction of the martensite twins to the magnetic field direction. The results are discussed with reference to different experimental procedures and the shape memory characteristics of the allo

EFFECT OF TEXTURING ON THE MAGNETICALLY ACTIVATED PROPERTIES OF POLYCRYSTALLINE NIMNGA ALLOYS

We present structural and magnetostrain data obtained on as cast and annealed bulk polycrystalline Ni2MnGa samples with a defined grain orientation. A peak cyclic strain of the order of 10-4 is found, due to the readjustment of martensite structures under applied field. Annealing may produce positive effects on the austenite to martensite transition and on strain. These experimental results are discussed with reference to previously published data on single crystals and randomly oriented polycrystalline samples