A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Damage Tolerance of Impacted Composite Sandwich Structures
This thesis deals with damage tolerance of impacted sandwich structures for load bearing applications. Composite sandwich structures find wide application as lightweight solutions in aerospace components, since weight reduction and less fuel emissions are primary concerns for aircraft manufactures. Sandwich structures are built of stiff face-sheet materials bonded to a low-density core material. In this thesis, the face-sheets are composite materials reinforced with carbon fibre non-crimp fabrics whereas the core consists of a closed cell foam material. Sandwich structures are susceptible to impact damage and even a small amount of damage can reduce the residual strength of components significantly. Therefore, damage tolerance assessment of such structures is essential and needs to be taken into account in the design process. Main objective of this thesis is assessment of test methodologies for estimation of compressive properties of foam core materials. An extensive experimental study of different densities of closed cell foam materials is presented and existing test standards are evaluated in this regard. Two different test methods were investigated for strain measurements of the foam material during compression testing assisted by a digital image correlation technique. A parametric study was also performed to investigate the effect of in-plane specimen size on the compressive modulus measurements. Both homogenized and stochastic finite element models are used to back the experimental observations. Different types of boundary conditions were used to simulate the effects of in-plane specimen size and prediction of compressive modulus. The findings were also used as basis for recommendations for updating current test standards. A part of the thesis work concerns the design and construction of a new drop-weight impact rig for low-velocity impact testing of sandwich structures. A test setup was designed to capture the true impact response without adulteration by oscillations. A novel catch mechanism was designed ...
Damage Tolerance of Impacted Composite Sandwich Structures
This thesis deals with damage tolerance of impacted sandwich structures for load bearing applications. Composite sandwich structures find wide application as lightweight solutions in aerospace components, since weight reduction and less fuel emissions are primary concerns for aircraft manufactures. Sandwich structures are built of stiff face-sheet materials bonded to a low-density core material. In this thesis, the face-sheets are composite materials reinforced with carbon fibre non-crimp fabrics whereas the core consists of a closed cell foam material. Sandwich structures are susceptible to impact damage and even a small amount of damage can reduce the residual strength of components significantly. Therefore, damage tolerance assessment of such structures is essential and needs to be taken into account in the design process. Main objective of this thesis is assessment of test methodologies for estimation of compressive properties of foam core materials. An extensive experimental study of different densities of closed cell foam materials is presented and existing test standards are evaluated in this regard. Two different test methods were investigated for strain measurements of the foam material during compression testing assisted by a digital image correlation technique. A parametric study was also performed to investigate the effect of in-plane specimen size on the compressive modulus measurements. Both homogenized and stochastic finite element models are used to back the experimental observations. Different types of boundary conditions were used to simulate the effects of in-plane specimen size and prediction of compressive modulus. The findings were also used as basis for recommendations for updating current test standards. A part of the thesis work concerns the design and construction of a new drop-weight impact rig for low-velocity impact testing of sandwich structures. A test setup was designed to capture the true impact response without adulteration by oscillations. A novel catch mechanism was designed ...
Damage Tolerance of Impacted Composite Sandwich Structures
Rajput, Moeen ud din Saeed (author)
2018-01-01
2018:46
Theses
Electronic Resource
English
composite sandwich , cellular , polymer , material characterization , modulus , non-crimp fabric , low velocity impact , vibration , uncertainty analysis , drop-weight impact , fractography , barely visible impact damage , X-ray microtomography , compression-after-impact , bending-after-impact , high speed image processing , damage resistance , damage tolerance , Aerospace Engineering , Rymd- och flygteknik
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