Vishwesh Dikshit

Enhancing interlaminar fracture characteristics of woven CFRP prepreg composites through CNT dispersion

The inter-ply characteristics of polymeric prepreg composites influence their interlaminar fracture toughness and the overall performance. This article embarks on engineering the inter-ply interfaces of carbon fiber reinforced polymer (CFRP) composites. A novel and practical technique for dispersion of multi-walled carbon nanotubes (MWCNTs) onto woven CFRP prepreg is presented. The interlaminar fracture toughness of these CFRP lay-ups was evaluated experimentally and compared with the regular (without any CNTs) specimen. Double cantilever beam and end notch flexure tests were conducted for interlaminar fracture studies. It was observed that the addition of MWCNTs in between the CFRP prepreg plies helps in strengthening the interface. There existed an optimum percentage in which these nanofillers should be added. The presence of nanotubes increased fiber bridging within the ply interfaces, which in turn controlled the inter-ply crack propagation. The findings and the mechanisms are discussed using the test data, SEM pictures, schematics, and scans of the fractured surfaces.

Performance evaluation of ProJet multi-material jetting 3D printer

ABSTRACT The purpose of this paper is to quantitatively evaluate the performance of a multi-material jetting 3D printer, ProJet 5500X, especially the capability for micro manufacturing. Unlike other single material 3D printer, ProJet 5500X uses photopolymers as the build material and wax as the support material. The building performance was evaluated by building a modified version of the standard benchmark model with a high-resolution printing mode. The dimensional error, forming quality and surface roughness of the printed parts have been measured and analysed using a microscope, a 3D coordinate measuring machine and a surface profilometer. Using wax as the support material, fine features as small as 0.25 mm, lateral features and sharper edges could all be properly built, despite the rough side surfaces observed in the printed part. Identical features (3 mm pins) were precisely built with an accuracy of 15 µm. The research provides first-hand detailed performance knowledge in the ProJet system for understanding the working principle and comparison with other 3D printing systems.

Investigation of Quasi-Static Indentation Response of Inkjet Printed Sandwich Structures under Various Indenter Geometries

The objective of this investigation was to determine the quasi-static indentation response and failure mode in three-dimensional (3D) printed trapezoidal core structures, and to characterize the energy absorbed by the structures. In this work, the trapezoidal sandwich structure was designed in the following two ways. Firstly, the trapezoidal core along with its facesheet was 3D printed as a single element comprising a single material for both core and facesheet (type A); Secondly, the trapezoidal core along with facesheet was 3D printed, but with variation in facesheet materials (type B). Quasi-static indentation was carried out using three different indenters, namely standard hemispherical, conical, and flat indenters. Acoustic emission (AE) technique was used to capture brittle cracking in the specimens during indentation. The major failure modes were found to be brittle failure and quasi-brittle fractures. The measured indentation energy was at a maximum when using a conical indenter at 9.40 J and 9.66 J and was at a minimum when using a hemispherical indenter at 6.87 J and 8.82 J for type A and type B series specimens respectively. The observed maximum indenter displacements at failure were the effect of material variations and composite configurations in the facesheet.

Investigation of out of plane compressive strength of 3D printed sandwich composites

In this study, the 3D printing technique was utilized to manufacture the sandwich composites. Composite filament fabrication based 3D printer was used to print the face-sheet, and inkjet 3D printer was used to print the sandwich core structure. This work aims to study the compressive failure of the sandwich structure manufactured by using these two manufacturing techniques. Two different types of core structures were investigated with the same type of face-sheet configuration. The core structures were printed using photopolymer, while the face-sheet was made using nylon/glass. The out-of-plane compressive strength of the 3D printed sandwich composite structure has been examined in accordance with ASTM standards C365/C365-M and presented in this paper.

Failure assessment of aluminum liner based filament-wound hybrid riser subjected to internal hydrostatic pressure

The present study describes the burst behavior of aluminum liner based prototype filament-wound hybrid riser under internal hydrostatic pressure. The main objective of present study is to developed an internal pressure test rig set-up for filament-wound hybrid riser and investigate the failure modes of filament-wound hybrid riser under internal hydrostatic burst pressure loading. The prototype filament-wound hybrid riser used for burst test consists of an internal aluminum liner and outer composite layer. The carbon-epoxy composites as part of the filament-wound hybrid risers were manufactured with [±55 o ] lay-up pattern with total composite layer thickness of 1.6 mm using a CNC filament-winding machine. The burst test was monitored by video camera which helps to analyze the failure mechanism of the fractured filament-wound hybrid riser. The Fiber Bragg Grating (FBG) sensor was used to monitor and record the strain changes during burst test of prototype filament-wound hybrid riser. This study shows good improvements in burst strength of filament-wound hybrid riser compared to the monolithic metallic riser. Since, strain measurement using FBG sensors has been testified as a reliable method, we aim to further understand in detail using this technique.

Fractography of Particle Strengthening Mechanisms at Interfaces in Prepreg Composites

This paper discusses the research conducted on prepreg composites interfaces engineered with, either carbon nanotubes (CNTs), or core shell micro-particles (CSMs). The emphasis is given on the fractography details that highlight various mechanisms involved in strengthening the ply-to-ply surface contacts due to the addition of these nanoand micro-particles.