Interlaced Z-pin structures

• US 5,736,222 A
• Filed: 03/19/1996
• Issued: 04/07/1998
• Est. Priority Date: 11/01/1995
• Status: Expired due to Term

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Childress, James J.
• Primary Examiner(s): CHOI, KATHLEEN L
• Application Number:
  US08/618,650
• Time in Patent Office: 749 Days
• Field of Search: 428/119.71, 428/112, 428/311.51, 428/318.4, 428/319.3, 428/316.6, 428/310.5, 428/99, 428/116
• US Class Current: 428/119
• CPC Class Codes: B29C 31/08 of preforms to be moulded, e.g. tablets, fibre reinforced preforms, extruded ribbons, tubes or profiles; Manipulating means specially adapted for feeding preforms, e.g. supports conveyors B29C31/066, B29C37/001, B29C43/085 take precedence
• CPC Class Codes: B29C 70/086 and with one or more layers of pure plastics material, e.g. foam layers applying a non-preformed coating, e.g. a gel-coat, B29C37/0025; with foam blocks B29C70/86
• CPC Class Codes: B29C 70/24 oriented in at least three directions forming a three dimensional structure
• CPC Class Codes: B29K 2105/04 cellular or porous
• CPC Class Codes: B32B 2305/022 Foam
• CPC Class Codes: B32B 5/00 Layered products characterised by the non- homogeneity or physical structure , i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
• CPC Class Codes: B32B 5/18 characterised by features of a layer of foamed material
• CPC Class Codes: B32B 5/32 at least two layers being foamed and next to each other
• CPC Class Codes: B64C 1/12 Construction or attachment of skin panels
• CPC Class Codes: B64C 2001/0072 from composite materials
• CPC Class Codes: E04C 2/296 composed of insulating material and non-metallic or unspecified sheet-material E04C2/288 takes precedence
• CPC Class Codes: Y02T 50/40 Weight reduction
• CPC Class Codes: Y10T 428/233 Foamed or expanded material encased
• CPC Class Codes: Y10T 428/23914 Interlaminar
• CPC Class Codes: Y10T 428/24008 including fastener for attaching to external surface
• CPC Class Codes: Y10T 428/24033 including stitching and discrete fastener[s], coating or bond
• CPC Class Codes: Y10T 428/24099 On each side of strands or strand-portions
• CPC Class Codes: Y10T 428/24107 including mechanically interengaged strands, strand-portions or strand-like strips
• CPC Class Codes: Y10T 428/24149 Honeycomb-like
• CPC Class Codes: Y10T 428/24174 including sheet or component perpendicular to plane of web or sheet
• CPC Class Codes: Y10T 428/24182 : Inward from edge of web or sheet
• CPC Class Codes: Y10T 428/249923 : Including interlaminar mechanical fastener
• CPC Class Codes: Y10T 428/249953 : Composite having voids in a component [e.g., porous, cellular, etc.]
• CPC Class Codes: Y10T 428/24996 : With internal element bridging layers, nonplanar interface between layers, or intermediate layer of commingled adjacent foam layers
• CPC Class Codes: Y10T 428/249961 : With gradual property change within a component
• CPC Class Codes: Y10T 428/249981 : Plural void-containing components
• CPC Class Codes: Y10T 428/249987 : With nonvoid component of specified composition
• CPC Class Codes: Y10T 428/249991 : Synthetic resin or natural rubbers

Abstract

Improved pin-reinforced sandwich structure ties the face sheets (typically on opposite sides of a foam core) together with a plurality of Z-pins that extend into each face sheet (through the core). The pins are arranged in a an interlaced configuration off-normal to provide crack resistance around fasteners for connecting the composite structure to other structural elements in aerospace applications.

Claims

1. A pin-reinforced sandwich structure, comprising:

(a) a core having opposed first and second surfaces defining a reference plane and a normal plane;

(b) a first face sheet adjacent the first surface;

(c) a second face sheet adjacent the second surface;

(d) a plurality of pins inserted into and terminating in the first and second face second face sheets and extending through the core to form a pin-reinforced sandwich structure, wherein the pins form an interlaced Z-pin region having an interlaced, ordered configuration of pins having at least a portion of the pins off-normal to the reference plane;

(e) a bore through the core and face sheets in the interlaced Z-pin region and

(f) a fastener in the bore wherein the Z-pin region has an areal density of pins in the range from about 0.375-1.50%.

2. The structure of claim 1 wherein the face sheets are adhered to the core.

3. The structure of claim 1 wherein the core is organic matrix resin foam.

4. The structure of claim 1 wherein the face sheets are fiber-reinforced resin composites.

5. The structure of claim 1 wherein the pins are metal, graphite, glass, or carbon having a Young'"'"'s modulus of at least about 10⁷.

6. A method for increasing crack resistance around fasteners in pin-reinforced composite structure as defined in claim 1, comprising the step of:

ordering the pins off-normal into an interlaced configuration around the fastener to provide support for the fibers and load transfer paths.

7. The structure of claim 2 where the core is organic matrix resin foam.

8. The structure of claim 7 wherein the face sheets are fiber-reinforced resin composites.

9. The structure of claim 8 wherein the pins are metal, graphite, glass, or carbon having a Young'"'"'s modulus of at least about 10⁷.

10. The structure of claim 1 wherein the fastener is immediately adjacent the bore.

11. The structure of claim 1 wherein the off-normal pins are angled up to about 45°

with respect to the normal.

12. The structure of claim 1 wherein the off-normal pins are skew to both the reference plane and to a normal plane perpendicular to the reference plane.

13. A pin-reinforced sandwich structure, comprising:

(a) a core having opposed first and second surfaces defining a reference plane and a normal plane;

(b) a first face sheet adjacent the first surface;

(c) a second face sheet adjacent the second surface;

(d) a plurality of pins inserted into and terminating in the first and second face second face sheets and extending through the core to form a pin-reinforced sandwich structure, wherein the pins form an interlaced Z-pin region having an interlaced, ordered configuration of pins having at least a portion of the pins off-normal to the reference plane;

(e) a bore through the core and face sheets in the interlaced Z-pin region and

(f) a fastener in the bore, wherein;

the face sheets are adhered to the core;

the core is a foam or a honeycomb;

the face sheets are fiber-reinforced resin composites; and

the pins in the interlaced Z-pin region are at an areal density in the range from about 0.375-1.50% to provide resistance to crack growth around the bore by providing load paths through the pins from the fastener to the face sheets.

14. The structure of claim 13 wherein the core is honeycomb.