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CAUL SHEET FOR POLYMERIC COMPOSITE PROCESSING

IP.com Disclosure Number: IPCOM000247850D
Publication Date: 2016-Oct-06

Publishing Venue

The IP.com Prior Art Database

Abstract

The invention relates to airfoil and airflow surface part production for gas turbine engines. Specifically, a novel caul sheet used to intensify pressure in a polymeric curing process and a method for producing the caul sheet are disclosed.

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CAUL SHEET FOR POLYMERIC COMPOSITE PROCESSING

TECHNICAL FIELD

    The invention relates to airfoil and airflow surface part production for gas turbine engines. Specifically, a novel caul sheet used to intensify pressure in a polymeric curing process and a method for producing the caul sheet are disclosed.

BACKGROUND

    Gas turbines include, but are not limited to, gas turbine power generation equipment and gas turbine aircraft engines. A gas turbine includes a core engine having a high pressure compressor to compress the air flow entering the core engine, a combustor in which a mixture of fuel and the compressed air is burned to generate a propulsive gas flow, and a high pressure turbine which is rotated by the propulsive gas flow and which is connected by a larger diameter shaft to drive the high pressure compressor. A typical front fan gas turbine aircraft engine adds a low pressure turbine (located aft of the high pressure turbine) which is connected by a smaller diameter coaxial shaft to drive a front fan (located forward of the high pressure compressor) and to drive an optional low pressure compressor (located between the front fan and the high pressure compressor). The low pressure compressor sometimes is called a booster compressor or simply a booster.

    The fan and the high and low pressure compressors and turbines have airfoils each including an airfoil portion attached to a shank portion. Rotor blades are those airfoils which are attached to a rotating gas turbine rotor disc. Stator vanes are stationary airfoils which are


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attached to a non-rotating gas turbine stator casing. Typically, there are alternating circumferential rows of radially-outwardly extending rotor blades and radially-inwardly extending stator vanes. When present, a first and/or last row of stator vanes (also called inlet and outlet guide vanes) may have their radially-inward ends also attached to a non-rotating gas turbine stator casing. Counterrotating "stator" vanes are also known. Minimizing engine weight for an aircraft application is a primary design objective. However, weight reduction is itself limited by the requirement to maintain component strength under the various loads experienced during operation.

    In order to reduce the weight of airfoil blades, polymeric compositions such as polymer matrix composites (PMCs) have been incorporated into airfoils, such as fan blades. Additionally, airfoils have been produced with surface coatings, such as polyurethane erosion coatings to withstand the operating conditions and potential for contact with foreign objects. Airfoils have been created using a thermosetting polymeric resin which is injected onto the pressure side of an airfoil and cured in an autoclave.

    In order to inject the resin and cure it in an autoclave, a flexible sheet of material is secured on top of the airfoil while in the autoclave and pressure is applied above the sheet of material to aid in the curing process of the thermosetti...