Venting system for use with composite structures

Ventilation – Hollow partition

Reexamination Certificate

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Details

C454S070000, C052S302100, C052S302300

Reexamination Certificate

active

06758743

ABSTRACT:

STATEMENTS REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
FIELD OF THE INVENTION
The present invention generally relates to composite structures, and more particularly, to a venting system for venting and/or filtering airflow entering/exiting at least a portion of a composite structure.
BACKGROUND OF THE INVENTION
Composite materials (such as those utilized in aircrafts, spacecrafts, watercrafts, and the like) are generally made up of a pair of outer face sheets and an inner core area. The outer face sheets can be made from a variety of materials such as, but not limited to, metals, carbon fiber reinforced plastic, and glass fiber reinforced plastic. In addition, these outer face sheets may be single layer or multi-layered structures. The cores of these composite materials are generally designed to be lightweight, yet provide structural integrity to the composite material. Due to the inherent structural characteristics of these core areas, air is inevitably trapped within them between the face sheets during fabrication of these composite materials and/or during a subsequent apparatus construction process (e.g., integrating the composite material into an aircraft, spacecraft, or watercraft).
Air trapped within the core areas of these composite materials tends to be problematic (amongst other instances) when utilizing these composite materials as components of an aircraft and/or spacecraft. More specifically, the pressure differential of the air trapped between the face sheets of the composite material and the air outside the composite tends to increase with elevation. This phenomenon, also referred to as “ascent induced pressure decay”, increases the risk of face sheet delamination due to pressure induced bond line failures. In other words, since air pressure inside the composite material may be greater than the air pressure outside the composite material (generally a function of distance from the Earth's surface), the outer face sheet may be pushed away from the core of the composite material by air pressure buildup, potentially resulting in damage to the composite material (and hence the aircraft/spacecraft).
Some attempts at addressing the problems associated with pressure differences between the core areas of composite materials and the external environment (e.g., the atmosphere) have included installing one or more vents on the interior face sheet of the composite material that faces the inner cavity of the fuselage or payload compartment of the aircraft/spacecraft. These “interior” vents potentially pose serious risks to sensitive payloads due to the presence of contaminants and debris (which are generally byproducts of the trimming and/or drilling steps of the composite material fabrication process) within the core area of the composite material. Other attempts have included the use of vents that are made from stainless steel screens reinforced by aluminum frames. These reinforced stainless steel and aluminum vents are generally affixed to vent holes in composite structures. However, these vents tend to be very expensive, difficult to integrate/install, and are generally uniquely designed for one particular application.
SUMMARY OF THE INVENTION
The present invention is generally directed to a system for venting composite materials. More specifically, the present invention is generally directed to a low cost venting system that is easily integrated directly onto/into face sheets of a wide variety of composite structures. Any appropriate type/configuration of composite structure may benefit from utilizing the venting system of the present invention. One particularly desirable application of the venting system is in the outer shell of a launch vehicle, an aircraft, a spacecraft, a rocket, or any other aerodynamic body that flies or otherwise travels through gaseous medium.
A first aspect of the invention relates to a venting assembly including a venting system and a composite structure (e.g., the composite material or an aircraft or spacecraft). Herein, reference to a “composite structure” or “composite material” generally refers to a structure/material having at least first and second face sheets and a core disposed between the first and second face sheets. These face sheets may each include one or more layers of material (i.e., may be composite structures themselves). The venting system of the first aspect generally includes a mounting assembly and a non-metallic venting medium. The mounting assembly generally enables the venting system to be interconnected with the composite structure at a first location and at least generally fluidly interconnected with a first air hole extending from an outermost extent of the composite structure at least within the core of the composite structure. In other words, the venting system may be associated with one of the face sheets in such a manner that the first air hole is at least substantially, and more preferably entirely, covered by the venting system. Alternatively, the venting system may be attached to an apparatus that is attached to the composite structure in such a manner that the first air hole is at least substantially covered by the apparatus, and that an apparatus hole in the apparatus fluidly interconnects the air hole of the composite structure with the venting system of the first aspect.
The venting medium of the first aspect of the present invention is generally capable of one or both filtering and controlling airflow at least between the core of the composite structure and an exterior environment (e.g., the atmosphere). The venting medium generally includes a perimeter region and an airflow region disposed inwardly of the perimeter region, and is designed in such a manner that the airflow region of the venting medium is generally free from direct contact with any other portion of the venting system. In other words, the airflow region of the venting medium generally does not touch the mounting assembly or any other component of the venting system.
Various refinements exist of the features noted in relation to the subject first aspect of the present invention as well. Further features may also be incorporated in the subject first aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. The airflow region in one embodiment of the venting medium may include a surface area of at least about 45 mm
2
. This surface area of the airflow region is generally defined by a major surface of the airflow region (i.e., a surface that is generally parallel to a lateral extent of the composite material) minus the cross-sectional areas (taken at the major surface) of corresponding airflow passages disposed therethrough. Some embodiment of the first aspect may include the venting medium having a filter mesh size ranging from about 3 microns up to about 5 microns; however, filter mesh sizes outside this range may be appropriate. The individual airflow passages of the airflow region in the case of the first aspect (and optionally, the perimeter region) of the venting medium may have cross-sectional areas ranging in size from about 7 microns
2
up to about 20 microns
2
. In other words, in the case of the airflow passages being substantially circular, the cross-sectional diameter of the airflow passages may range from about 3 microns up to about 5 microns. In the case of the airflow passages exhibiting a polygonal, elliptical, or irregular (multi-angled and/or multi-radial) configuration, at least one cross-sectional length extending between two different points along the configuration may fall within the previously stated range of 3 microns up to about 5 microns. In some embodiments of this first aspect, it may be appropriate to utilize a venting medium having airflow passages outside the above-disclosed range.
The venting medium of one embodiment of this first aspect may generally exhibit an outgassing characteristic quantified by a maximum Total Mass Loss (TML) of no more than about 1%. In other words, an amount of material, which makes up v

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