| 1. |
- Sisodia, Sanjay M., et al.
(författare)
-
High-resolution computed tomography in resin infused woven carbon fibre composites with voids
- 2016
-
Ingår i: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 131, s. 12-21
-
Tidskriftsartikel (refereegranskat)abstract
- Tomographic imaging using both microfocus radiation and synchrotron radiation was performed to assess the void defects in resin transfer moulded woven carbon fibre composites. The focus of this study is on characterising the void homology (e.g. local void size and spatial distribution) in relation to weave orientation, infusion direction and potential effects on damage formation in tensile loading. As the orientation angle between the fibre direction of unidirectional layer in the laminate and the direction of the global resin flow increases, from parallel to perpendicular, larger voids and a greater volume fraction of voids were observed, which led to increased damage formation upon loading. Significant accumulation of voids around both the layer interfaces and yarn fibres were also observed. With regard to yarn design, it is recommended to balance the benefits (e.g. fabric handling, structural integrity of preform) and drawbacks (e.g. lower fibre content, more voids) of the supporting yarn. Also, sensible placement of resin inlets and outlets could reduce the amount of deleterious voids, i.e. by promoting resin flow along the fibre direction in the most defect-sensitive off-axis layers.
|
|
| 2. |
- Sisodia, Sanjay, et al.
(författare)
-
The effects of voids in quasi-static indentation of resin-infused reinforced polymers
- 2019
-
Ingår i: Journal of composite materials. - : SAGE Publications. - 0021-9983 .- 1530-793X. ; 53:28-30, s. 4399-4410
-
Tidskriftsartikel (refereegranskat)abstract
- The focus of this study is the influence of voids on the damage behaviour in quasi-static loading of resin-infused carbon fibre-reinforced polymers. Experimental results are presented for quasi-static loading in combination with high-resolution tomographic imaging and statistical analysis (homology of pores or voids and induced cracks). Three distinct mechanisms were observed to control delamination growth in the presence of sharp and blunt voids. Delamination cracks interact with the supporting yarns, especially in combination with air pockets trapped in the resin in the form of long, sharp voids. This resulted in crack growth that coalesces with delamination cracks from neighbouring yarn-voids during increased out-of-plane load-displacement, with almost no presence of intralaminar transverse cracks. This highlights the benefits and drawbacks of the supporting yarn during out-of-plane loading.
|
|
| 3. |
- Sisodia, Sanjay, et al.
(författare)
-
CHARACTERISATION OF VOIDS AND THEIR INFLUENCE ON DAMAGE PROPAGATION IN RESIN INFUSED CARBON FIBRE REINFORCED POLYMERS
- 2015
-
Konferensbidrag (refereegranskat)abstract
- High-performance structural composite components have historically been most often manufactured with prepreg materials cured in an autoclave oven. To remain cost-competitive, it is generally assumed that in the future an increasing fraction of parts will be manufactured with a faster, less expensive process such as liquid composite moulding (LCM). The weakness of LCM processes is the generally higher void content compared with prepreg and autoclave processing, due to entrapment of bubbles during infusion. The effect of voids on the resulting mechanical properties is still relatively unclear, especially for heterogeneous void distributions, which is always the case in LCM. Intuitively it is expected that void parameters such as size, shape, location, clustering, and local concentration would play a role in damage development and failure, but their relative effects are currently not well understood. A better understanding of these micromechanisms could ideally give some indications as to how to supress damage formation and improve the mechanical performance.This study focuses on the formation of voids in resin transfer moulded carbon fibre reinforced polymers and their effect on damage development that ultimately leads to final failure. This was done by characterising voids in the resin of the cured laminates using X-ray computed tomography (CT), and by looking at the material failure mechanisms associated with in-plane and out-of-plane behaviour. Laminate coupons were tested under low cycle tension fatigue and low velocity out-of-plane impact/indentation. The void distribution was found to be heterogeneous with voids nucleating in plies where the fibre orientation was not parallel to the flow direction, at the ply interfaces, and along woven yarns. In out-of-plane loading, multiple cracks/delaminations were seen to interact with these void regions. As a consequence of increased loading, these delaminations grew and coalesced with their neighbours to form a single larger delamination prior to final failure. In open-hole, in-plane tension fatigue testing, larger voids resulted in delaminations initiating at the void. Transverse (out-of-plane) cracks are seen to form around smaller voids.
|
|
