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TECHNIQUE TO EDGE GRIND CERAMICS MATRIX COMPOSITES IN GREEN STATE

IP.com Disclosure Number: IPCOM000240472D
Publication Date: 2015-Feb-03
Document File: 3 page(s) / 56K

Publishing Venue

The IP.com Prior Art Database

Abstract

The invention proposes a technique to create smooth flat edge side surface of ceramics matrix composites (CMCs) in green state. The technique uses nanosecond pulse green laser to grind the edge and create a flat or smooth edge finish without risk of chipping and delamination. The pulse laser provides a non-contact machining means to create smooth flat edge side surface of CMCs. The pulsed laser ablates the green state CMC layer by layer till it creates a smooth flat edge side surface. A software program is applied to generate a close loop laser scan two dimensional (2D) profile. The 2D profile includes one side matching the final finishing edge which is either straight or curved lines.

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TECHNIQUE TO EDGE GRIND CERAMICS MATRIX COMPOSITES IN GREEN STATE

BACKGROUND

The present invention relates generally to green state ceramics matrix composites (CMCs) and more particularly to a technique for forming flat edge side of green state CMCs.

Generally, green state ceramics matrix composites (CMCs) include silicon carbide-silicon carbide (SiC-SiC) performs. Green state CMC is attained before the composite passes through melt infiltration and oven burn out stages.

Usually the green state CMC panel edge side is not flat and requires to be machined to smooth surface for next step attachment to rest of the assembly. The rough panel edge of CMC is due to variation of length or size of each layer of plies.

A conventional technique utilizes mechanical grinder to achieve smooth edge side finish for the green stage CMC performs. The technique further requires liquid coolant to avoid any thermal shock during grinding of edges of CMC due to better thermal conductivity and improved fracture toughness of the coolant.  However, mechanical grinder provides a risk of generating chipping and delamination. Also coolant supply provides contamination into the CMC material and affects the final property.

It would be desirable to have an efficient technique to create a smooth flat edge side surface of CMCs in green state such that the edge is neither chipped nor delaminated.

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DETAILED DESCRIPTION

The invention proposes a technique to create a smooth flat edge side surface of ceramics matrix composites (CMCs) in green state. The technique uses nanosecond pulse green laser to grind the edge and create a flat or smooth edge finish. The pulse laser provides a non-contact machining means to create smooth flat edge side surface of CMCs. The pulsed laser ablates the green state CMC layer by layer till it creates a smooth flat edge side surface. Also laser scan path occurs from outside the CMC edge side to avoid beam clipping due to open kerf and laser divergence angle.

The technique selects a solid state pulse laser which has very high peak power density, typically, from a few tens of megawatts to gigawatts per centimeter square (GW/cm2). Such high power density pulse laser removes the green state CMC by direct ablation. Also the green wavelength, typically, at about 532 nm or 517 nm and nano-second pulse duration helps to achieve good laser energy absorption on silicon carbide (SiC) material of CMCs and minimize thermal damage. A software program is applied to generate a close loop laser scan two dimensional (2D) profile. The 2D profile includes one side matching the final fin...