Failure modes of unidirectional carbon/epoxy composite compression specimens

Odom, Edwin; Adams, Donald F.

doi:10.1016/0010-4361(90)90343-u

Cited by 63 publications

(22 citation statements)

References 3 publications

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“…There is a good classification of failure modes in compression described by Odom and Adams [9]. The typical failure modes described there were found.…”

Section: Evaluation Of Failure Mechanismsmentioning

confidence: 92%

“…They may consist of already existing debondings (microcracks), defects in the laminate structure (resin pockets or terminated plies), fractured fibres at the surface in consequence of specimen preparation, etc. As pointed out by Odom and Adams [9], the occurrence of a certain kind of failure strongly depends on the type of tabbing material, the tab geometry and how effectively the specimen is gripped. Both first items were not changed during round robin testing herein.…”

Section: Evaluation Of Failure Mechanismsmentioning

confidence: 98%

“…A comprehensive study of failure modes was done by Odom and Adams [9]. They found five main failure modes in carbon/epoxy composites: transverse, branched transverse and split transverse failure, which are very similar; and two more: brooming and shear failure.…”

mentioning

confidence: 99%

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Determination of Compressive Properties of Fibre-Reinforced Polymers in the In-Plane Direction According to ISO 14126. Part 2: A Critical Investigation of Failure Behaviour

Schneider

Lauke

2007

Appl Compos Mater

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In Part 1 of this paper, we have compared the compression modulus and compressive strength obtained during a round robin test with the so-called Celanese-type equipment in four laboratories. The scatter of the measured values was considerable, with a variation coefficient of about 10% for the modulus and about 15% for the compressive strength. The main source responsible for this disappointing result is supposed to lie in the stress/strain concentrations induced by the tabs that support the specimen and transfer the load from the machine to the specimen. Detailed optical examinations have shown that cracks are initiated in this region or at least run into it after being initiated away from the tabs. Additionally, the local deformations were determined during testing with a grating technique. The local strains in different directions agree qualitatively with the results of finite-element modelling of the Celanese-type testing. The strain concentrations near the free surface of the tabs, which are responsible for the crack initiation, can be reduced if the tabs do not have a sharp 45°edge but a certain curvature.

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“…There is a good classification of failure modes in compression described by Odom and Adams [9]. The typical failure modes described there were found.…”

Section: Evaluation Of Failure Mechanismsmentioning

confidence: 92%

Section: Evaluation Of Failure Mechanismsmentioning

confidence: 98%

See 1 more Smart Citation

Determination of Compressive Properties of Fibre-Reinforced Polymers in the In-Plane Direction According to ISO 14126. Part 2: A Critical Investigation of Failure Behaviour

Schneider

Lauke

2007

Appl Compos Mater

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“…The resin was cured, and the tubing removed, leaving behind the cylindrical braided composite sample with a fiber volume fraction of 52%. These samples were cut into 12.5 mm long pieces, and their ends coated with SCI epoxy to prevent brooming failure 58 and glued to a pair of platens. They were then tested in compression as shown in …”

Section: Compressionmentioning

confidence: 99%

“…The cylindrical samples were then cut into 20 mm long pieces, which were sufficiently stocky to ensure avoidance of Euler buckling, their ends coated with SCI epoxy to prevent brooming failure 62 , attached to slotted tabs and tested in compression at ambient temperature (23º C) at a strain rate of 2x10 -4 s -1 . The elastic modulus for each sample was measured by unloading within the nominally elastic region of the stress-strain curve.…”

Section: Axial Compressionmentioning

confidence: 99%

Carbon Fiber Composite Cellular Structures

George

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Ultralight sandwich panel structures which utilize light, stiff, and strong face sheets, and stiff, strong, compressible cellular cores have attracted significant research interest for use in aerospace and energy absorption applications. The cores of these sandwich structures are typically fabricated using high strength cellular materials, such as aluminum and titanium alloys, or polymer foams and honeycombs. However, for weight sensitive, ambient temperature applications, carbon fiber composites have emerged as a promising material due to its high specific strength and low density. Carbon fiber reinforced polymer (CFRP) composite cellular materials, when combined with structurally efficient sandwich panel designs, offer new opportunities for fabricating ultralight structures. This dissertation explores carbon fiber and carbon fiber hybrid sandwich panel design concepts, details the novel fabrication methods which have been developed for these structures, investigates the mechanical performance of the structures made using these approaches, and develops micromechanical models which predict the relationships between the mechanical properties of these structures and parent material properties, unit cell topology, and core density.The dissertation develops four fabrication approaches for making carbon fiber and carbon fiber hybrid sandwich structures. These include a mechanical snap fitting and adhesive bonding method, a braided carbon fiber net method, a simplified linear braid approach, and a pultruded rod/linear tow technique. CFRP lattice structures made from carbon fiber laminates using a mechanical snap-fitting and adhesive bonding technique have been found to have high strength in through-thickness compression and in-plane iii shear. However, under compression or shear loading, these structures typically fail abruptly, exhibiting little ability to support load after initial strut failure. The trusses are also brittle, and absorb little energy during impact. The braided net fabrication approach utilizes a braided carbon fiber net within polymer and syntactic foams to form the core, woven carbon fiber face sheets, polymer and syntactic foam molds, and Kevlar stitching of core to the face sheets, followed by vacuum assisted resin transfer molding. This approach has facilitated the fabrication of empty lattice (truss and face sheet only) and hybrid core specimens ranging in density from 35 -478 kg/m 3 , and the mechanical performance of these structures characterized. The cellular structures made using this approach have been shown to have high compressive and shear strengths, as well as excellent energy absorption capacity. The linear braid method represents a simplified fabrication approach which utilizes linear braids to form the trusses within a hybrid cellular material. This method has facilitated the manufacture of hybrid cellular materials with a truss volume fraction ranging from 1.5 -17.5% of the core. The fraction of the truss contained in the nodes is found to lead to saturation in core streng...

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