Indentation and impact damage in carbon fibre-reinforced polymer composite materials
File(s)
Author(s)
Brooks, Richard
Type
Thesis or dissertation
Abstract
The issue of climate change has led to an increased focus on efficiency and reduction of emissions in the aerospace sector. Large improvements in fuel efficiency have been achieved through the use of lightweight composite materials. The impact behaviour of these composite materials, particularly carbon fibre-reinforced polymers (CFRPs), is complex and highly dependent on a number of variables. Therefore, this thesis focuses on the impact behaviour of CFRP and the resulting damage formed by low-velocity impacts.
Low-velocity impacts usually initiate internal damage within CFRP which must be viewed and analysed using non-destructive testing (NDT) methods. In most cases, an indentation is also formed on the surface of the CFRP. The results of this thesis show that a larger surface indentation depth corresponds to a larger delamination damage area. However, an indentation appears to initiate before the development of any delamination damage.
The effect of previous damage within a structure was investigate by performing two low-velocity impacts in different locations on the same panel, separated by varying distances. The resulting delamination damage area and the residual compression-after-impact (CAI) strength were measured. The results highlight that multiple impacts close to each other are more detrimental to the structural integrity of a component than impacts separated by larger distances.
Once damage has been detected and analysed, a decision must be made on whether to replace the whole component or whether to perform a repair. A repair increases the complexity of the damage process, therefore this thesis has also focused on the impact behaviour of patch-repaired CFRP. Low-velocity impact testing in the centre of circular patch repairs highlighted that thicker patches show a lower delamination damage area than thinner patches. The greatest reductions in damage area were however seen through the addition of a plug of material beneath the patch.
Low-velocity impacts usually initiate internal damage within CFRP which must be viewed and analysed using non-destructive testing (NDT) methods. In most cases, an indentation is also formed on the surface of the CFRP. The results of this thesis show that a larger surface indentation depth corresponds to a larger delamination damage area. However, an indentation appears to initiate before the development of any delamination damage.
The effect of previous damage within a structure was investigate by performing two low-velocity impacts in different locations on the same panel, separated by varying distances. The resulting delamination damage area and the residual compression-after-impact (CAI) strength were measured. The results highlight that multiple impacts close to each other are more detrimental to the structural integrity of a component than impacts separated by larger distances.
Once damage has been detected and analysed, a decision must be made on whether to replace the whole component or whether to perform a repair. A repair increases the complexity of the damage process, therefore this thesis has also focused on the impact behaviour of patch-repaired CFRP. Low-velocity impact testing in the centre of circular patch repairs highlighted that thicker patches show a lower delamination damage area than thinner patches. The greatest reductions in damage area were however seen through the addition of a plug of material beneath the patch.
Version
Open Access
Date Issued
2024-05-21
Date Awarded
2024-09-01
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Dear, John
Li, Nan
Sponsor
Comac (Firm)
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)