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Aviation History
1942
1942 - 2275.PDF
OCTOBER 29TH, 1942 FLIGHT 477 PLASTIC PROGRESS means of " Plastel " these can be stiffened where necessary, particularly around the edges. In a general way it brings steel back into competition with light alloys for this and many other purposes, and if stainless steel is used, the material has the added attraction of non-corrodibility. A New Adhesive Another product of Aero Research, Ltd., which has actually been in use for over two years but only recently released from the secret list, is an adhesive by the tra'de name "Ardux." From the description given by Dr. de Bruyne, " Ardux " is an adhesive capable of joining phenol-formaldehyde or urea formaldehyde mouldings or laminated sheet with such efficiency that the shear strength of the joint usually exceeds that of the parent material. The following extract from a report issued by the Royal Aircraft Estamishment is striking evidence of the strength of '' Ardux'' joints: "We have now tested these joints and enclose a table giving the failing loads. The tests were made with the standard glued-joint grips. " As in every case the fractured area showed shearing of the parent material rather than the joint failure, the adhesion was efficient, and joints may be regarded as of satisfactory strength. Group Group 1 : fin. thick laminated impregnated paper material Group 2: 1/loth in. thick paper reinforced synthetic resin sheet. Failing Load lb. 913 500 550 560 412 Mean apparent Shear Stress at Failure in lb. sq. in. 913 1,000 1,100 1,120 824 '' In group 1 failure occurred largely by the shearing of the synthetic resin material, only small areas of glue failure being visible. In group 2 failure occurred entirely by shear ing of the plastic material, no glue failure could be seen." '' Ardux " is a suspension of powder in a reactive resin and is unique in its speed of setting and its reliability, this combination giving results hitherto unattainable with exist ing synthetic resin cements for Bakelite materials. " Ardux " is applied to the surfaces to be joined, which are then left for a few minutes to become tacky (a gentle warming will hasten this process) and finally clamped together with an ordinary G clamp. The joint must then be heated to not less than 140 deg. C, (284 deg. F.). At 155 deg. C. "Ardux 1" will set in six minutes. "Ardux 2 " is not quite so fast in setting. Roughening of the sur faces is not necessary- since '' Ardux '' does not depend upon mechanical keying for its adhesion and is equally efficient applied to highly polished surfaces. Where flat sheets are to be joined the heat can be conveniently applied by clamping the joint to a steam-heated hot-plate. "Ardux 1" should be used for well-fitting joints and Hinge between two pieces of cellulose acetate, made with " Plastel." The metal is stabbed all over with small burred holes, thus locking it "to the plastic. "Ardux 2" for metal inserts and where gap joints have to be made. '' Ardux '' has no specific adhesion for metals, but it can be used with great success to secure metal inserts into mouldings and laminated sheets if the root end of the metal insert is knurled. The necessary hole may be drilled, or it can be made in the moulding operation. It should be of such a diameter that the metal insert is a good push fit. Simple knurling is sufficient, the grooves or threads being not more than 1/64m. deep, other wise the adhesive will not expand sufficiently to fill them. '' Ardux'' is applied to the hole and the metal insert pushed in; heat can then be applied. This is most con veniently done by bringing the protruding end of the metal insert into contact with a heated block. An electrically heated soldering iron is convenient for small jobs, but where large numbers of inserts have to be fixed it is worth while making a jig for the purpose. "Ardux" is officially approved as an adhesive for synthetic resin materials for aircraft uses. In my previous article "Plastics and Aircraft" (Flight. September 14th and 24th and October 1st), it was sug gested that means should be provided to dispense with metal fittings which still appear necessary where main structural joints are required, and that this could be over come to some extent by providing plastic inserts cemented to the wood structure to obtain the required strength in bearing. It is interesting to record, therefore, that the De Havil- land Aircraft Company have for some time now been using a fabric-reinforced plastic material cemented to wooden members of aircraft to give additional local strength. The bearing strength is some four to five times greater than that of hardwood, and the material is not susceptible to warping or shrinking; furthermore, it has no grain to encourage splitting. Inserts of this material cemented to wood on each side have been used for tailplane spar roots and other joints to increase bearing strength around bolt holes. In thinner form it can be used for floor coverings in cockpits, and in this case has the advantage of being impervious to the action of oil or petrol. The Society of British Aircraft Constructors are very much alive to the value of plastics in aircraft construction, and every effort is being made to provide the manufac turers and their designers with the latest data available from the plastics industry. For example, The British Plas tics Federation records a request from the S.B.A.C. for the preparation of schedules of properties for various plastics and resins for the benefit of aircraft manufacturers. The Federations Plastic Materials Section has appointed sub committees to collate the required data. NON-FERROUS METAL URGENTLY NEEDED THOUSANDS of slow-going hazardous sea miles lie between vital natural sources of metal supply and the hands that must fashion this metal into munitions. Copper, lead, tin, rinc—mined in Africa. North and South America and Australia—are urgently wanted in pure form for work: and as urgently required because they provide between them in alloyed form brass, bronze and anti-friction bearing metal. Two miles of copper wire are needed for a bomber, as well as brass for instruments, aluminium for fuselage and fittings, and anti-friction metal for engine bearings. The production of guns, tanks, shells, bullets and numerous other forms of equipment for the Fighting Forces all demand thousands of tons of non-ferrous metals. To speed up the supply of non-ferrous metals and to save as much shipping as possible, the Ministry of Supply has issued an urgent appeal for all unwanted copper, zinc, lead, pewter, white metal, brass, bronze and scrap aluminium. Firms connected with the aeronautical industry are asked to search out all useless non-ferrous metal they may hold and send it either to the nearest local depot or to a scrap metal merchant.
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