Critical Failure Modes in Cracked Mechanically Fastened Stiffened Panels

2009 ◽  
pp. 310-310-18
Author(s):  
CK Gunther ◽  
JT Wozumi
Keyword(s):  
Failure Modes ◽  
Stiffened Panels ◽  
Mechanically Fastened

The Effects of Seawater Immersion on the Bearing Strength of Woven-Glass–Epoxy Prepreg Pin-Loaded Joints

2011 ◽  
Vol 21 (2) ◽  
pp. 153-170 ◽  
Author(s):  
AyŞe Öndürücü
Keyword(s):  
Failure Modes ◽  
Failure Load ◽  
Diameter Ratio ◽  
Hole Diameter ◽  
Natural Seawater ◽  
Bearing Strength ◽  
Specimen Width ◽  
Bearing Load ◽  
Mechanically Fastened ◽  
Ultimate Failure

This study considers the bearing strengths and failure modes of woven-glass–epoxy prepreg composite mechanically fastened joints. For the study, the specimens were immersed in natural seawater in the laboratory for over 1 year. The edge distance-to-hole diameter ( E/ D) ratio and the specimen width-to-hole-diameter ratio ( W/ D) were systematically altered during experiments. Failure modes were determined by observing the failure regions on the specimens. Damage progression in pin-loaded specimens prepared from woven-glass–epoxy prepreg was also examined using a scanning electron microscopy for three different percentages of ultimate failure load. According to the experimental investigation results, it was observed that the bearing load values obtained from the specimens immersed in seawater decreased considerably in comparison to unimmersed specimens.

A Review of Damage Tolerant Design, Certification and Repair in Metals Compared to Composite Materials

2014 ◽  
Vol 891-892 ◽  
pp. 1597-1602 ◽  
Author(s):  
Nabil Chowdhury ◽  
Wing Kong Chiu ◽  
John Wang
Keyword(s):  
Composite Materials ◽  
Composite Structures ◽  
Failure Modes ◽  
Structural Integrity ◽  
Fiber Reinforced Polymers ◽  
Carbon Fiber Reinforced Polymers ◽  
Reinforced Polymers ◽  
Repair Efficiency ◽  
Mechanically Fastened ◽  
Damage Tolerant

A review of some of the various fatigue models introduced over the years for both metallic materials, in particular aluminium alloys followed by fatigue and durability concerns associated with composite materials. The move towards light weight and high stiffness structures that have good fatigue durability and corrosion resistance has led to the rapid move from metal structures to composite structures. With this brings the added concern of certifying new components as the damage mechanisms and failure modes in metals differ significantly than composite materials such as carbon fiber reinforced polymers (CFRP). The certification philosophy for composites must meet the same structural integrity, safety and durability requirements as that of metals. Hence this is where the challenge now lies. Substantial work has been conducted in the reparability of composite structures through bonding using various adherend thicknesses and joint types and has been shown to have higher durability than mechanically fastened repairs for thin adherends however these are currently unacceptable repair methods as they cannot be certified. Repairs are designed on the basis that the repair efficiency can be predicted and should be designed conservatively with respect to the various failure modes and include the surrounding structure.

scholarly journals Study on Mechanical Bearing Strength and Failure Modes of Composite Materials for Marine Structures

2021 ◽  
Vol 9 (7) ◽  
pp. 726
Author(s):  
Dong-Uk Kim ◽  
Hyoung-Seock Seo ◽  
Ho-Yun Jang
Keyword(s):  
Composite Materials ◽  
Failure Mode ◽  
Composite Structures ◽  
Failure Modes ◽  
Offshore Structures ◽  
Fiber Reinforced ◽  
Bearing Strength ◽  
Fiber Reinforced Plastic ◽  
Reinforced Plastic ◽  
Mechanically Fastened

With the gradual application of composite materials to ships and offshore structures, the structural strength of composites that can replace steel should be explored. In this study, the mechanical bearing strength and failure modes of a composite-to-metal joining structure connected by mechanically fastened joints were experimentally analyzed. The effects of the fiber tensile strength and stress concentration on the static bearing strength and failure modes of the composite structures were investigated. For the experiment, quasi-isotropic [45°/0°/–45°/90°]2S carbon fiber-reinforced plastic (CFRP) and glass fiber-reinforced plastic (GFRP) specimens were prepared with hole diameters of 5, 6, 8, and 10 mm. The experimental results showed that the average static bearing strength of the CFRP specimen was 30% or higher than that of the GFRP specimen. In terms of the failure mode of the mechanically fastened joint, a cleavage failure mode was observed in the GFRP specimen for hole diameters of 5 mm and 6 mm, whereas a net-tension failure mode was observed for hole diameters of 8 mm and 10 mm. Bearing failure occurred in the CFRP specimens.

Experiments on Top-Hat–Stiffened Panels of Fiber-Reinforced–Plastic Boat Structures

2007 ◽  
Vol 44 (01) ◽  
pp. 1-15
Author(s):  
Ömer Eksik ◽  
R. Ajit Shenoi ◽  
Stuart S. J. Moy ◽  
Han Koo Jeong
Keyword(s):  
Failure Modes ◽  
Matrix Cracking ◽  
Uniform Pressure ◽  
Structural Stiffness ◽  
Fiber Reinforced ◽  
Experimental Procedure ◽  
Stiffened Panels ◽  
Fiber Reinforced Plastic ◽  
Pressure Load ◽  
Reinforced Plastic

The paper outlines an experimental procedure devised to assess the strength of top-hat-stiffened panels under uniform pressure load. Structural stiffness issues and their dependence on lay-up have been explored. The nature of the failure, from matrix cracking through the final collapse, is detailed. Included in the discussion is the nature of failure modes and their linkage to lay-up design. Numerous strain and digital dial gauges were used to collect important information.

Effect of Pressure on Collapse Behaviour of Stiffened Panel

2014 ◽  
Author(s):  
Lei Jiang ◽  
Shengming Zhang
Keyword(s):  
Finite Element ◽  
Failure Modes ◽  
Lateral Pressure ◽  
Initial Pressure ◽  
Offshore Structures ◽  
Numerical Results ◽  
Stiffened Panel ◽  
Longitudinal Stress ◽  
Stiffened Panels ◽  
Hull Girder

During normal operations, ship and offshore structures, are subjected to combined lateral pressure and in-plane stresses. The effect of the lateral pressure is often ignored in hull girder ultimate assessments. This paper investigates the influence of the lateral pressures on the nonlinear collapse behavior of stiffened panels subjected to in-plane longitudinal stress. In this study, nonlinear finite element analyses were first conducted for the desired pressure alone; the longitudinal stress was then applied up to and beyond the collapse of the structures. Four representative stiffened panels taken from the bottoms of different double hull oil tankers were considered. The nonlinear analyses were performed using LR’s in-house finite element program VAST and following the procedure for nonlinear collapse analysis developed by LR. The numerical results indicated that the application of the initial pressure loads not only reduced the ultimate load carrying capacity of the panels significantly, but also changed the failure modes of the structures. The sensitivity of the ultimate strength to lateral pressure was dependent upon the panel geometry and whether the pressure was applied on the plate or the stiffener side. The numerical results and findings from this study are presented in this paper.

Structural Life Expectancy of Marine Vessels: Ultimate Strength, Corrosion, Fatigue, Fracture, and Systems

2015 ◽  
Vol 1 (1) ◽  
Author(s):  
Bilal M. Ayyub ◽  
Karl A. Stambaugh ◽  
Timothy A. McAllister ◽  
Gilberto F. de Souza ◽  
David Webb
Keyword(s):  
Structural Reliability ◽  
Failure Modes ◽  
Structural Integrity ◽  
Structural Response ◽  
Probabilistic Methods ◽  
Life Assessment ◽  
Operational Environment ◽  
Stiffened Panels ◽  
Factors Affecting ◽  
Marine Vessels

This paper provides a methodology for the structural reliability analysis of marine vessels based on failure modes of their hull girders, stiffened panels including buckling, fatigue, and fracture and corresponding life predictions at the component and system levels. Factors affecting structural integrity such as operational environment and structural response entail uncertainties requiring the use of probabilistic methods to estimate reliabilities associated with various alternatives being considered for design, maintenance, and repair. Variability of corrosion experienced on marine vessels is a specific example of factors affecting structural integrity requiring probabilistic methods. The Structural Life Assessment of Ship Hulls (SLASH) methodology developed in this paper produces time-dependent reliability functions for hull girders, stiffened panels, fatigue details, and fracture at the component and system levels. The methodology was implemented as a web-enabled, cloud-computing-based tool with a database for managing vessels analyzed with associated stations, components, details, and results, and users. Innovative numerical and simulation methods were developed for reliability predictions with the use of conditional expectation. Examples are provided to illustrate the computations.

Scanning Electron Microscopy in Hybrid Microelectronics

1976 ◽  
Vol 34 ◽  
pp. 456-457
Author(s):  
S. Khadpe ◽  
R. Faryniak
Keyword(s):  
Integrated Circuits ◽  
Thick Film ◽  
Integrated Circuit ◽  
Failure Modes ◽  
Three Dimensional ◽  
Circuit Components ◽  
Hybrid Microcircuit ◽  
Electrical Connections ◽  
Scanning Electron

The Scanning Electron Microscope (SEM) is an important tool in Thick Film Hybrid Microcircuits Manufacturing because of its large depth of focus and three dimensional capability. This paper discusses some of the important areas in which the SEM is used to monitor process control and component failure modes during the various stages of manufacture of a typical hybrid microcircuit.Figure 1 shows a thick film hybrid microcircuit used in a Motorola Paging Receiver. The circuit consists of thick film resistors and conductors screened and fired on a ceramic (aluminum oxide) substrate. Two integrated circuit dice are bonded to the conductors by means of conductive epoxy and electrical connections from each integrated circuit to the substrate are made by ultrasonically bonding 1 mil aluminum wires from the die pads to appropriate conductor pads on the substrate. In addition to the integrated circuits and the resistors, the circuit includes seven chip capacitors soldered onto the substrate. Some of the important considerations involved in the selection and reliability aspects of the hybrid circuit components are: (a) the quality of the substrate; (b) the surface structure of the thick film conductors; (c) the metallization characteristics of the integrated circuit; and (d) the quality of the wire bond interconnections.

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