1,721,038 research outputs found
Elastoplastic Behaviour of Composite Laminates
No full textDuctile matrix composites undergo plastic deformation even at low stress levels. In this paper the elastoplastic behaviour of APC2 (AS4/PEEK) laminas is studied by means of a one-parameter plastic potential. The extension to laminates of constitutive relations that are based on this yield function is examined; a comparison is made between experimental data and numerical results obtained by integrating the elastoplastic relations for various stacking sequences monotonically loaded. Results are also shown regarding notched strength prediction of angle-ply laminates with a circular hole, based on an elastoplastic behaviour assumption
Damage Assessment in Graphite-Peek Laminates with and without a Hole Subjected to Fatigue Loading
No full textCharacterization of fracture modes in stitched and unstitched cross-ply laminates subjected to low-velocity impact and compression after impact loading
No full textThe insertion of transverse reinforcing threads by stitching is a very promising technique to restrict impact damage growth and to improve post-impact residual strength of laminates. In order to develop general models capable of addressing the issues of impact resistance and damage tolerance of stitched laminates, detailed understanding of the nature and extent of damage, identification of the dominant fracture modes and assessment of the effect of stitches on the damage development are essential. In this study, both instrumented drop-weight tests and compression-after-impact tests were carried out to examine and compare the damage responses of stitched and unstitched graphite/epoxy laminates subjected to low-velocity impact. The progression of damage and its effect on post-impact performance was investigated in detail in two classes of cross ply laminates ([03/903]s and [0/90]3s) by means of an extensive series of damage observations, conducted with various complementary techniques (X-radiography, ultrasonics, optical microscopy, deply). The results of the analyses carried out during the study to characterize the key fracture modes and to clarify their relationship with the structural performance of both stitched and unstitched laminates are reported and discussed in the paper
Damage Evolution in Stitched and Unstitched Graphite/Epoxy Laminates Subject to Low-Velocity Impact
No full textThe response to low velocity impact loadings, which may occur during manufacturing, service and maintenance, is a key factor in the design of composite material structures. Many techniques, ranging from the adoption of tough matrices/high-strain fibers to the introduction of through-thickness reinforcement, have been proposed to improve the damage response of composite laminates subject to impact. The insertion of transverse reinforcing threads by stitching, in particular, appears very promising to restrict damage growth and to improve post-impact performance of laminates. In order to develop general models capable of addressing the issues of damage tolerance and resistance, detailed understanding of the nature and extent of damage, identification of the dominant fracture modes and assessment of the effect of stitches on the damage development are essential. In this study instrumented drop-weight tests were carried out to examine and compare the damage response of stitched and unstitched cross-ply graphite/epoxy laminates subject to low-velocity impact. The progression of damage and its relationship with impact and absorbed energy were investigated by means of an extensive series of damage observations, conducted with various techniques (X-radiography, ultrasonics, optical microscopy, deply)
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