Mechanical Strength Degradation of Graphite Fiber Reinforced Thermoset Composites Due to Porosity

Uhl, K. M.; Lucht, Brad; Jeong, Hwan Jeong; Hsu, David K.

doi:10.1007/978-1-4613-0979-6_24

Cited by 17 publications

(25 citation statements)

References 10 publications

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“…Using the manual tomography method, Olivier et al 103 developments had happened in perpendicular direction to fibers; larger voids were present mainly between the plies (inter-laminar), and the voids were in contact with the fibers, which caused local change in the distribution of surrounding fibers. The elongated morphology of voids in UD-ply composites is reported in many other studies and expressed with different terminology such as ''elliptically cylindrical'', 89 ''cylindrical inter-laminar'', 221 ''cigar-shaped'', 222,223 ''large and long'', 224 ''flat and elliptical in cross-section'', 146 ''flattened'', 101 ''rod-like shape'', 97,128 and ''cylindrically shaped''. 203 The change in the void morphology with the void content in UD-ply composites, reported by Stone and Clarke, 99 was endorsed by Stamopoulos et al 198 through micro-CT analysis of voids, where the authors showed that the shape of the voids changed from ''spherical'' or ''ellipsoidal'' to a ''needle-shape'', when the void content increased.…”

Section: Void Contentmentioning

confidence: 71%

Voids in fiber-reinforced polymer composites: A review on their formation, characteristics, and effects on mechanical performance

Mehdikhani

Gorbatikh

Verpoest

2018

Journal of Composite Materials

544

305

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Voids, the most studied type of manufacturing defects, form very often in processing of fiber-reinforced composites. Due to their considerable influence on physical and thermomechanical properties of composites, they have been extensively studied, with the focus on three research tracks: void formation, characteristics, and mechanical effects. Investigation of voids in composites started around half a century ago and is still an active research field in composites community. This is because of remaining unknowns and uncertainties about voids as well as difficulties in their suppression in modern manufacturing techniques like out-of-autoclave curing and parts with high complexity, further complicated by increased viscosity of modified resins. Finally, this is because of the increasing interest in realization of more accurate void rejection limits that would tolerate some voidage. The current study reviews the research on formation, characterization, and mechanical effects of voids, which has been conducted over the past five decades. Investigation and control of void formation, using experimental and modeling approaches, in liquid composite molding as well as in prepreg composite processing are surveyed. Techniques for void characterization with their advantages and disadvantages are described. Finally, the effect of voids on a broad range of mechanical properties, including inter-laminar shear, tensile, compressive, and flexural strength as well as fracture toughness and fatigue life, is appraised. Both experimental and simulation approaches and results, concerning voids' effects, are reviewed.

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Section: Void Contentmentioning

confidence: 71%

Voids in fiber-reinforced polymer composites: A review on their formation, characteristics, and effects on mechanical performance

Mehdikhani

Gorbatikh

Verpoest

2018

Journal of Composite Materials

544

305

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“…Similar to the work published by Uhl et al [17] and Lee and Soutis [18,19], the calculation of the updated material strength due to porosity was done according to the relation…”

Section: A Extended Non-destructive Testing Modulementioning

confidence: 99%

Material Selection for a Curved C-Spar Based on Cost Optimization

Kaufmann

Zenkert

Åkermo

2011

Journal of Aircraft

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A case study for the cost optimization of aircraft structures based on the operating cost as objective function is presented. The proposed optimization framework contains modules for estimation of the weight, manufacturing cost, non-destructive inspection cost and structural performance, the latter enhanced by a kinematic draping model which allows the fiber angles to be simulated more realistically. The case study includes five material systems:

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“…With regard to new material systems, optimized manufacturing methods and more accurate NDT techniques, this porosity level is about to be challenged. A lot of work has been performed to investigate in the effect of the laminate thickness and the laminate porosity on the mechanical properties [22][23][24][25][26][27]. It was concluded that the compressive strengthσ c degrades exponentially.…”

Section: Strength Reduction Due To Porositymentioning

confidence: 99%

“…The value of B = −3.14 was adopted from Uhl et al [23] who performed a number of test series for a 16 ply quasi-isotropic carbon/epoxy laminate. The void content v p as function of the thickness was required as input.…”

Section: Case Studymentioning

confidence: 99%

Cost optimization of composite aircraft structures including variable laminate qualities

Kaufmann

Zenkert

Mattei

2008

Composites Science and Technology

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Composite structures can lower the weight of an airliner significantly. The increased production cost, however, requires the application of costeffective design strategies in which cost, weight and the desired laminate quality are taken into account. This paper proposes an optimization framework for composite aircraft structures that minimizes the direct operating cost on a part level. In addition to previous models, a nondestructive testing model is implemented that calculates design allowables of a laminate based on ultrasonic scan parameters. In a case study, the effect of the laminate quality on the direct operating cost is discussed. It is investigated how the permissible flaw size and therefore the scan pitch of a composite laminate can influence the optimal solution in terms of cost and weight; thus, the manufacturing cost, the non-destructive testing cost and the weight of a component can be balanced by optimizing the laminate quality in an early design phase.

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Mechanical Strength Degradation of Graphite Fiber Reinforced Thermoset Composites Due to Porosity

Cited by 17 publications

References 10 publications

Voids in fiber-reinforced polymer composites: A review on their formation, characteristics, and effects on mechanical performance

Voids in fiber-reinforced polymer composites: A review on their formation, characteristics, and effects on mechanical performance

Material Selection for a Curved C-Spar Based on Cost Optimization

Cost optimization of composite aircraft structures including variable laminate qualities

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