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in the 0o plies was observed at high load levels. No visible delamination was observed in the specimens of both laminates before the final catastrophic fracture.
Delamination was only observed in the fractured specimens after tests. These results imply the suppression effect of high fracture toughness of PA6 on the delamination initiation.
4) The configurations of fiber distribution and cracks on the different widthwise sections exhibit some changes of a certain degree because of the micro-scale waviness or misalignment of fiber bundles. Similar to the matrix cracks at the free edge, matrix cracks also occurred and progressed in the fiber dense regions along the widthwise direction.
5) The failure mechanism of the present Maruhachi and TenCate cross-ply laminates under tension was concluded to be a sequence of five damage stages: (1) matrix cracks initiated in the fiber dense regions in the 90° plies at the tensile strain around 0.3%; (2) Existing cracks extended and new cracks increased in the 90°
plies as the tensile strain increased from 0.3% to 0.8%, and larger transverse cracks were arrested in the vicinity of the interface between the 0° and 90° plies;
(3) Fiber breakage occurred in the 0° plies at the strain higher than 0.8% because of the stress concentration caused by the transverse cracks in the adjacent 90°
plies; (4) Fiber breaks accumulated in the 0° plies as the tensile strain further increased from 0.8% to 1.5%, resulting the reduction in the tensile strength of the 0° plies; and (5) one 0° ply or multiple 0° plies fractured at the tensile strain close to 1.5% and then the specimen catastrophically fractured at the same instant.
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Conclusions and future works
This chapter summarizes the main conclusions of this dissertation and discusses the main research topics concerning this study in future.
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