Claims
- 1. A method of bonding a plurality of articles together, at least one of which is ceramic, by placing a polymeric adhesive in contact with and between the articles and applying pressure, and optionally heat, to said articles wherein the improvement comprises:
- (a) applying to a surface of the at least one
- ceramic article prior to placing adhesive on
- the surface a layer comprising M.sub.x (OR).sub.y or
- mixtures thereof, wherein
- (i) x is 1;
- (ii) y is 3 or 4;
- (iii) M is silicon or magnesium; and
- (iv) R is an organic radical;
- (b) exposing the ceramic article having the M.sub.x (OR).sub.y layer
- thereon to moisture and a temperature of about 25.degree. C.
- to about 300.degree. C. prior to contact with the adhesive; resulting in a joint resistant to crack propagation.
- 2. The method of bonding as recited in claim 1 wherein at least one of the articles is a fiber reinforced polymeric composite.
- 3. The method of bonding as recited in claim 1 wherein at least one of the article is a fiber reinforced ceramic composite.
- 4. The method as recited in claim 1 wherein M is silicon.
- 5. The method as recited in claim 1 wherein M is magnesium.
- 6. A plurality of articles bonded to one another through a layer of polymeric adhesive, at least one of said articles, being a ceramic article wherein the improvement comprises the at least one ceramic article having a layer of amorphous hydrated metal oxide thereon and in contact with the adhesive layer, the layer of amorphous hydrated metal oxide being formed by application onto the ceramic article and subsequent hydrolysis of a layer comprising M.sub.x (OR).sub.y or mixtures thereof, where
- (a) x is 1;
- (b) y is 3 or 4;
- (c) M is silicon or magnesium; and
- (d) R is an organic radical; resulting in a bond resistant to crack propagation.
- 7. The bonded articles of claim 6 wherein at least one article is a fiber reinforced polymeric composite.
- 8. The bonded articles of claim 6 wherein at least one article is a fiber reinforced ceramic composite.
- 9. The bonded articles of claim 6 wherein M is silicon.
- 10. The bonded articles of claim 6 wherein M is magnesium.
TECHNICAL FIELD
This is a continuation of application Ser. No. 911,580, filed Sept. 24, 1986 now abandoned. CROSS REFERENCE TO RELATED APPLICATION
Attention is directed to commonly assigned U.S. Patents entitled "Amorphous Hydrated Metal Oxide Primer for Composite Fibers", U.S. Pat. No. 4,678,820 and "Amorphous Hydrated Metal Oxide Primer for Organic Adhesively Bonded Joints, U.S. Pat. No. 4,623,591, which disclose material similar to that used in the present application, the disclosures of which is hereby incorporated by reference.
The field of art to which this invention pertains is adhesively bonded joints and methods for adhesively bonding joints.
Weight saving and manufacturing cost benefits have led to the increase in use of adhesively bonded structures in the aircraft and aerospace industries. In order to be a viable alternative to, for example, metal fasteners, these adhesive bonds should maintain the strength typical of conventional fastener systems. In many applications the bonds are put under a variety of environmental and mechanical stresses. For example, frequently these bonds are exposed over long periods of time to wet environments which can result in a loss of bond strength. The loss of strength can result from the extension of cracks and other deformations that occur in the adhesive and which are exacerbated by the moist environment. As a result of this deficiency, extensive research and development efforts have been undertaken to define methods and identify materials which improve bonded joint performance in humid conditions. For example, it is known that surface preparation is important in the bonding of aluminum and titanium. Also, when bonding to ceramic surfaces roughness or porosity and cleanliness are important. Thus, it is essential that before bonding, the adherend is cleaned and chemically pretreated to produce a surface which combines with the adhesive to develop the bond strengths which meet application requirements. A variety of pretreatments for aluminum have been developed to produce improved bondability. These include acid etching (FPL), and anodized treatments with sulfuric (SA), chromic (CAA) and phosphoric acid (PAA). The latter, PAA, is generally accepted as the most effective surface treatment in terms of bond strength and durability at the present time. It has been shown by in depth surface analysis using scanning transmission electron microscopy that the PAA treatment produces fine oxide protrusions of greater length and magnitude than other surface treatments. These whiskers are believed to account for the strength enhancement achieved with joints made using PAA treated adherends. Thus, mechanical interlocking by whisker reinforcement of an adhesive appear to play a role in enhancing adhesive bonding. Porosity in ceramic articles may play a similar role in adhesion to such materials. The probability that chemical interaction is of major importance, depending upon the adhesive/article compositional combination, is also believed. Although the above surface preparations have provided advantages, there is a need for new technology to aid in the advancement of lightweight aerospace-type structures.
Accordingly, there is a constant search in this field of art for new methods of providing lightweight, structurally sound, adhesively bonded joints.
This disclosure is directed to bonded joints resistant to crack propagation. A plurality of articles are bonded to one another through a layer of polymeric adhesive at least one of said articles being a ceramic article. At least one of the ceramic articles has a layer of amorphous hydrated metal oxide thereon and in contact with the adhesive layer. The layer of amorphous hydrated metal oxide is formed by application onto the ceramic article and subsequent hydrolysis of, a layer comprising M.sub.x (OR).sub.y or mixtures thereof. In the formula M.sub.x (OR).sub.y, x is 1, y is 3 or 4, M is any metal capable of forming a stable alkoxide and R is an organic radical.
Another aspect of this invention is a method of bonding a plurality of articles together that results in a joint resistant to crack propagation. The method comprises placing a polymeric adhesive in contact with and between the two articles and applying pressure and optional heat to the articles. A layer comprising M.sub.x (OR).sub.y or mixtures thereof is applied to a surface of at least one of the ceramic articles prior to placing adhesive on the surface. In the formula M.sub.x (OR).sub.y, x is 1, y is 3 or 4,M is any metal capable of forming a stable alkoxide and R is an organic radical. The ceramic article having M.sub.x (OR).sub.y layer thereon is exposed to moisture and a temperature of about 25.degree. C. to about 300.degree. C. prior to contact with the adhesive.
This amorphous metal oxide primer for adhesively bonded joints provides bonds that are more resistant to crack propagation. Thus, this invention makes a significant advance to the aerospace industry by providing new technology relating to adhesive bonding.
Other features and advantages will be apparent from the specification and claims and from the accompanying drawings which illustrate an embodiment of the invention.
US Referenced Citations (7)
Foreign Referenced Citations (1)
| Number |
Date |
Country |
| 654049 |
Jun 1951 |
GBX |
Non-Patent Literature Citations (2)
| Entry |
| Pike, "Inorganic Primers to Bonded Joints and Fiber Reinforced Resin Composites", International Adhesion Conference, 9-1984. |
| Paper presented at The International Adhesion Conference 1984 titled "Inorganic Primers in Bonded Joints and Fiber Reinforced Resin Composites" by Roscoe A. Pike, Sep. 12-14, 1984, University of Nottingham, London, England. |
Continuations (1)
|
Number |
Date |
Country |
| Parent |
911580 |
Sep 1986 |
|
Patent Grant
4853300
