Composite Material Damage Processes

Abstract

Composite materials are in use in the shipbuilding industry for a long period of time. Composites appear in vast number of fibre – matrix combinations and can be produced with several different production processes. Due to the specific nature of the composite material structure, the selection of the production process and the limitations in the quality control procedures, composite materials will always be subject to defects and imperfections which may, under certain circumstances, lead to the appearance and propagation of cracks. The size and the shape of the crack, the load type and the stress field in the material surrounding the crack will be crucial for crack growth and crack propagation. This paper reviews the composite material damage processes especially relevant for shipbuilding. The basic principles of composite material fracture mechanics are briefly explained, and finally, mechanisms responsible for the development of damage and fracture of composite materials are presented. This paper has emerged from the need to summarize information about composite material fracture and failure mechanisms and modes relevant for the shipbuilding industry.

A Review on Mechanical Performance of Hybrid Natural Fiber Polymer Composites for Structural Applications

“…There are three different modes of fracture failures (1) Mode I crack—opening mode where a tensile stress is normal to the plane of the crack, (2) Mode II crack—sliding mode where shear stress acts parallel to the plane of the crack and perpendicular to the crack front, and (3) Mode III—tearing mode where a shear stress acts parallel to the plane to the plane of the crack and parallel to the plane of the crack and parallel to the crack front [ 106 ]. Bolf et al [ 107 ] elaborate on the crack in the composites based on the opening mode where the crack will usually propagate in the direction of the fiber. However, after the test, the crack will propagate through the matrix regardless of the direction of loading or the angle of the fiber.…”

“…Delamination is also noticeable as crack propagation that happens between layers of composite materials. According to studies, delamination frequently starts at free edges and/or at discontinuities arising from matrix cracking; in addition, bridging and dynamic effects such as strong interaction between different mechanisms may rise at multiple length scales [ 107 , 108 ].…”

“…Delamination in sandwich laminate occurs when the sandwich plates separate from the core with the laminate skins. This occurrence may occur due to one of these factors, including the insufficient core preparation, surface impurities, or premature application of the next layer of laminate as the laminate was subjected to a certain load: for instance, compression or flexion [ 107 , 109 ]. The failure can be caused by stress concentration, low velocity, manufacturing defects, etc.…”

“…Through this process, materials will experience their initial cracks or imperfection especially after a number of cycles and continue to expand and propagate [ 113 ]. According to Bolf et al [ 107 ], a composite material subjected to fatigue loads will go through these five features: (1) breakage of the matrix and/or fibers, (2) crevice cracking, matrix fiber peeling, and/or breakage of fiber, (3) delamination, (4) crack growth through delamination and fiber breakage, and (5) breakage of the materials.…”

Application of Apriori Algorithm in the Lamination Process in Yacht Production

“…Such defects may occur in both the gelcoat and the structural laminate. A small amount of small air bubbles in the structural laminate is natural and does not significantly reduce the strength properties of the laminate, but large bubbles act as dry reinforcement and weaken the strength of the element [4]. Air bubbles (A) in the gelcoat layer can cause faster degradation of the protective layer, which is the gelcoat, and allow water to penetrate the structural laminate [23].…”