Design optimization of a CFRP–aluminum joint for a bioengineering application

Lightweight design demands and complexity requirements of modern high-end structures in aerospace, automotive, sports and bioengineering can be successfully covered by a combination of fiber reinforced polymers (FRPs) with metallic components. Conventionally, mechanical locking is favored in integrating multi-material parts, avoiding bonded interfaces. The feasibility of a multi-material carbon FRP–aluminum structural component of a robotic exoskeleton, fabricated in a single step with the FRP directly cured on the aluminum domain, was investigated. To conduct the feasibility analysis, pertinent systematic FE modeling involving cohesive contact was employed to optimize the design, while strength and fracture testing were conducted to define the formed interfaces’ resistance. Sandblasting treatment was also investigated and compared with plain surfaces. The results show that the effect of residual stresses due to curing process governs the created joint’s durability. To reduce their effect, the local compliance of the multi-material components was altered by introducing a compliant layer along with modification of the aluminum domains’ local geometry in a manner that does not compromise the overall structural integrity. The interface stresses of the optimized geometry are a few times lower than the ones estimated for the initial design. The methodology adopted herein delivers some guidelines on treating such problems.

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

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.891-892.1597 ◽

2014 ◽

Vol 891-892 ◽

pp. 1597-1602 ◽

Cited By ~ 1

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.

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Enhancement of Mechanical Integrity of Advanced Composites using PMAA-Electropolymerised CF Fabrics

MATEC Web of Conferences ◽

10.1051/matecconf/201818801007 ◽

2018 ◽

Vol 188 ◽

pp. 01007

Author(s):

Dionysios A. Semitekolos ◽

Panagiotis Goulis ◽

Despoina I. Batsouli ◽

Elias P. Koumoulos ◽

Loukas Zoumpoulakis ◽

...

Keyword(s):

Carbon Fiber ◽

Carbon Fibers ◽

Structural Integrity ◽

Fiber Reinforced Polymers ◽

Nanoindentation Test ◽

Mechanical Interlocking ◽

Hot Press ◽

Carbon Fiber Reinforced Polymers ◽

Reinforced Polymers ◽

Advanced Composites

The aim of the present study is the development of new composite materials that show improved mechanical and structural integrity. In order to accomplish this goal, a novel functionalization method of the carbon fibers for the reinforcement of the composites surface was investigated. Through the electrografting of methacrylic acid onto the surface of the carbon fiber, this treatment aims to selectively modify the surface of the carbon fabrics, in order to create active groups that can chemically react with the epoxy resin, under heat and pressure. By this way, better adhesion as mechanical interlocking between the resin and the reinforcement can be achieved. The surface treatment was examined qualitatively by means of Infrared spectroscopy, Scanning Electron Microscopy and Raman spectroscopy. The carbon fiber reinforced polymers were manufactured via the hot-press technique and they were subsequently submitted to flexural, shear and nanoindentation test. Finally, the internal structural integrity was tested through micro-Computing Tomography.

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Lightweight Design with Long Fiber-Reinforced Polymers - Technological Challenges Due to the Effect of Fiber Matrix Separation

Plastics Engineering ◽

10.1002/j.1941-9635.2017.tb01642.x ◽

2017 ◽

Vol 73 (1) ◽

pp. 48-49

Author(s):

Christoph Kuhn ◽

William Kucinski ◽

Olaf Taeger ◽

Tim A. Osswald

Keyword(s):

Lightweight Design ◽

Fiber Reinforced Polymers ◽

Fiber Reinforced ◽

Reinforced Polymers ◽

Matrix Separation ◽

Fiber Matrix

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Experimental investigation on stiffness and strength of single-lap z-pinned joints in a laminated CFRP stress-ribbon strip

The Baltic Journal of Road and Bridge Engineering ◽

10.3846/bjrbe.2016.14 ◽

2016 ◽

Vol 11 (2) ◽

pp. 120-126 ◽

Cited By ~ 4

Author(s):

Aleksandr K. Arnautov ◽

Vladimir Kulakov ◽

Janis Andersons ◽

Viktor Gribniak ◽

Algirdas Juozapaitis

Keyword(s):

Structural Integrity ◽

Progressive Failure ◽

Failure Process ◽

High Strength ◽

Lap Joints ◽

Fiber Reinforced Polymers ◽

Fiber Reinforced ◽

Reinforced Polymers ◽

Load Bearing ◽

Hybrid Joints

Carbon fiber-reinforced polymer (carbon-polymer) is an advanced lightweight composite material with high strength and excellent resistance to corrosion and fatigue. Over the past decades, application of fiber-reinforced polymers has been spread from the aerospace to other branches of industry such as automobile and civil engineering. Unidirectional carbon-polymers have a high potential for replacing steel in tensile members. Recently, the first carbonpolymer stress-ribbon bridge has been constructed in Germany. The non-laminated strip-loop carbon-polymer thin strips were used as the load bearing components in this bridge. In comparison with the laminated components, the applied cables are characterized by a more uniform strain distribution though reduced structural integrity. Alternative jointing technologies of carbon-polymer laminates are considered in this paper with an intention to increase the structural integrity and reliability of the production. Tensile behavior of the single-lap joints was investigated experimentally. Three types of the joints were considered. Adhesive joint was set as the reference. The overlap region of the mechanically fastened joints was produced using 9, 25, or 36 steel needles (z-pins) of 1 mm diameter. The proposed hybrid joints were additionally connected with adhesive increasing the load-bearing capacity of the reference joint up to 230%. Concerning the brittle fracture of the adhesive counterparts, the extended progressive failure process within the hybrid joints is responsible for the improvement.

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Development of a Health Monitoring Capability for FRP Using Optical Fiber Sensors

10.1115/imece2001/nde-25811 ◽

2001 ◽

Author(s):

Christopher Cassino ◽

John Duke ◽

Jason Borinski

Keyword(s):

Optical Fiber ◽

Health Monitoring ◽

Life Cycle Cost ◽

Structural Integrity ◽

Optical Fiber Sensor ◽

Fiber Reinforced Polymers ◽

Reinforced Polymers ◽

Fiber Sensors ◽

Accumulated Strain ◽

Bridge Superstructure

Abstract Fiber reinforced polymers (FRP) are an efficient and relatively inexpensive method of repairing or replacing deteriorating and damaged infrastructure. FRP sheets can be applied to spalling bridge sections to prevent further deterioration and increase stiffness. Pre-fabricated FRP decks can also be used to replace weak portions of the bridge superstructure. However, the effect of the environment on long-term durability of FRP and how the various mechanisms of deterioration initiate and develop are not known. Systems for health monitoring are being sought as a means of managing transportation structures as assets in light of modern life cycle cost concepts. This paper will describe the efforts to develop a method to monitor the structural integrity of FRP materials utilizing an optical fiber sensor developed by Luna Innovations. This sensor is capable of detecting both transient, acoustic emission strain events as well as the accumulated strain in the components to which it is attached. The fact that this sensor is impervious to electromagnetic radiation makes it ideal for monitoring FRP in transportation applications.

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