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Testing of Defence Materials

The testing of defence materials is needed for their stability and compatibility. Their shelf life design work needs to be carried out in order to create a product, which can obtain a high storage reliability under different climatic conditions.
Exova CMK performs all methods of testing to ensure reliability and, most importantly, the safety of the product being used.

Specialist Service Offerings

HUMID The program HUMID is designed as a tool to guide the development work on a product towards a high storage reliability under different climatic conditions. As an early help in this work the program will give suggestions of the design in the form of drying agents, sealings and constructional materials. The program is specially intended for the following purposes: - To simplify the choice of materials and the design of seals and plastic walls to obtain an optimum storage reliability. The consequences of different choices of material can rapidly become apparent by testing different alternative designs and study the results after simulated storage. - To give suggestions about how different moisture protections shall be dimensioned. Sometimes it is sufficient to utilize the moisture absorbing components that already are present in the design. In other cases there is a need to add a reinforcement in the form of, for instance silica gel. The program will then give an indication of the amounts that are needed. - To orient about the storage properties of the object in different environments. Computations with moist environments and environments with large temperature variations can give information, to which type of climate the object is most sensitive. Thereby one will get information of value in the selection of climate profiles for climatic chamber tests. HUMID is a computer program, which step-by-step calculates moisture migration within an object exposed to a certain temperature/humidity environment. The program is a convenient tool to perform simulations during a long time period with the effort of a computer time of a few minutes or less. The program is built up with event codes and is menu oriented. It can only be used in the Windows environment. The object studied should be of the type ”a container in a container in a container....” with a maximum of four concentric spaces in the design. The object becomes the following shape in the electrical analogy. The simplest way to define an annual climate is to choose for each month the average night temperature during the month as the minimum temperature and the average maximum day temperature as the maximum temperature. The relative humidities at the minimum and at the maximum temperature should also be stated. In this way we get 24 temperatures and 24 relative humidities representing the climatic profile for the year. The object should be analyzed in detail from a moisture point-of-view. Each possible route for the moisture should be identified and the individual routes should be characterized. This is valid for plastic walls, seals as well as pores and slits through the barriers. especially the last types of routes are important to define, since temperature changes will result in air transport through openings in the walls. The program contains a small data bank with information of permeability coefficients and activation energies for a number of materials often used in designs. Constructional designs often contain more or less hygroscopical materials that can bind water. Moisture entering such a space will partly be bound to these materials and partly to stay in the air mass and contribute to the relative humidity in the object. The program contains a small data bank for the most common hygroscopical materials used. The program is equipped with the possibility to include materials with tendency to react with moisture in the calculations, for instance metallic materials, which corrode in humid atmosphere. In such cases it is naturally necessary to investigate how the rate of the process is influenced by relative humidity and temperature. The program is equipped with a very detailed manual with lots of examples of different practical cases.
Material investigations
Shelf life design work during development How long will this product last? It is easy to ask the question but a reliable answer often needs an extensive investigation. The shelf life of polymeric materials (e.g. plastics and rubbers) depends on how the product is manufactured, how it is used and to which environment it is exposed. For this investigation Exova uses a procedure in several steps. The firs step is a shelf life analysis of the product, next step is to test the components under accelerated conditions and finally a varifying test is carried out under moderately accelerated conditions. The shelf life analysis implies that all components of the product are catalogued in a data base. The probability for a single component to deteriorate is considered from the environmental factors to whitch it might be exposed. Thereafter the risk of affecting the product function is taken into account. At this stage defective designs are often discovered and changes of design or materials can be recommended. The next step involves testing of the most critical components under accelerated conditions. After that it is often possible to estimate the shelf life. The shelf life is finally verified by testing the complete product at accelerated conditions. Figure 1. Correctional cost as a function of a product’s developement phase Figure 2. Optimizing of environmental test
Stability and compatibility tests The question whether two materials influence each other or not can preferably be studied with microcalorimetry. It is possible to find out if there is any interaction between the materials when they are in direct contact as well as when they are separated from each other in a closed space. Problems concerning compatibility are especially important in connection with shelf-life estimations of complete products containing several different material types. Exova has used microcalorimetry to study material interactions for a long time. A typical question is whether two materials in a product are interacting, either when they are in direct contact or when they are exposed to each other by gas formed components from some of the materials in a closed space. The investigation includes measurements of the heat flows generated by the separate components as well as the heat flow generated by adequate mixtures of the two materials. The test can be designed with different grade of contact between the materials, with different weight rates and at different temperatures. From the tests it is possible to estimate the degree of interaction and get information enough to recommend suitable material combinations in a design. Figure 1. Microcalorimetry study of compatibility. Figure 2. Determination of degree of interaction. Completing analysis techniques: Weight loss test Example of studied materials: Polyamide, explosives
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Locations which specialise in this service are listed below.

Exova Karlskoga The Karlskoga laboratory offers a full range of mechanical testing services. Failure analysis and advice on materials, selection of metals as well as polymers. Exova also has a number of special techniques aiming to ensure the shelf life of new munitions (please visit www.bomic.com for more information) and in service surveillance of old ammunition. We now have clients from all over the World. Amongst the laboratory specialist services are scanning electron microscopy, micro-calorimetry, chemical analysis, failure analysis, environmental durability tests etc. Exova Box 431 Gammelbackavägen 6 Karlskoga 69151 Sweden Enquiries Telephone: +46 586 824 02 E-Mail: info@exova.com

Exova Linköping Exova offers qualified impartial services and long-term co-operation in Materials and Process Technology from development and design to maintenance/production and recycling. Having a history from the Swedish defence and aircraft industry we have specialist competence within the area of aerospace materials technology. Based on that experience, we have expanded our services to a wide range of industrial areas. Examples are: Nuclear, Wind Power, Manufacturing, Automotive and Electronics. In all these areas, our customers require the high competence within materials engineering CSM represents. Exova Box 1340 Gelbgjuregatan Linköping 58113 Sweden Enquiries Telephone: +46 13 16 90 18 E-Mail: info@exova.com

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