Section 2 Core material

2.1.1 The requirements of this section make provision for the in situ production of a solid elastomeric material between two steel plates thus forming a steel sandwich panel.

2.1.2 The elastomer properties when, tested to a suitable standard, shall be agreed with LR and formed in situ by use of base components approved by LR.

2.1.3 The base component manufacturer must hold valid LR certification, based on an agreed schedule of tests and inspection of his facilities and quality control procedures.

2.1.4 The mixing of the base components and the injection of the mix to form the elastomer is to be carried out according to a written procedure approved by LR.

2.1.5 Base components are to be provided with unique identifications by their manufacturers.

2.1.6 No batch is to be used later than its date of expiry, except with the prior agreement of LR and new certificate of conformity being obtained from the base component manufacturer.

2.1.7 The Builder is to ensure that batches are stored in accordance with the manufacturer's instructions and are used systematically and sequentially.

2.2.1 The following information is to be submitted by the Design Organisation:

1. Material specifications and tolerances.

2. Listing of materials used.

3. Method and site of manufacture, and suppliers of components.

4. Evidence of selected manufacturer's or sub-contractor's ability to produce the core material in accordance with the design specification. This shall be confirmed in each case by an agreed schedule of tests representative of the production being carried out in the presence of an LR Surveyor.

2.2.2 It is the responsibility of the Design Organisation to ensure that materials and components are available to the appropriate specification prior to commencement of manufacture.

2.3.1 The base component manufacturer is to provide the Builder with certificates of conformity for each batch of material supplied indicating the relevant values specified in Ch 2, 2.5 Material testing. These values are to comply with those specified by the approved specification.

2.3.2 The Builder is to ensure copies of certificates of conformity (which must indicate the actual tested values) are obtained for batches of materials received, and is to maintain accurate records. LR may at any time select a sample of a material for testing by an independent source and should such tests result in the material failing to meet specification, the batch will be rejected.

2.4.1 For incoming base materials, irrespective of whether or not the Builder conducts his own tests or is reliant on the manufacturer for certificates of conformity the following is to be carried out, where applicable, on receipt of any material.

1. The consignment is to be divided into its respective batches and each batch is to be labelled accordingly.

2. Each batch is to be visually examined for conformity with the batch number, visual quality and expiry date.

3. Each batch is to be separately labelled and stored accordingly.

4. Each unit within the batch is to be labelled with the batch number.

5. Written records are to be maintained of the above and these are to be cross-referenced with the certificate of conformity for the material and/or the Builder's own test results.

2.4.2 Ready use components are to be maintained in stirred tanks at the temperatures recommended by the manufacturer. If these are above ambient then suitable calibrated temperature measuring devices are to be maintained.

2.5.1 The elastomer is currently based on polyurethane technology, hence the following tests should be conducted on the base components by the manufacturer:

1. Polyol

   1. Viscosity

   2. Moisture content (see Note)

   3. Hydroxyl value

2. Iso-cyanate

   1. Viscosity

   2. Iso-cyanate value

2.5.2 The Builder of the sandwich panels must mix the individual components of the elastomer under controlled conditions and measure the following properties according to recognised standards to a schedule acceptable to LR:

1. Density

2. Hardness

3. Shear modulus

4. Tensile stress

5. Tensile strain to failure

6. Bond shear strength.

2.5.3 Recognised standards to which specimens of elastomer are to be tested are listed in Table 2.2.1 Cured elastomer properties. In addition, if the deviation of one result exceeds the mean by more than two standard deviations, that result is to be discarded and one further specimen tested, see also Figure 2.2.1 Cured elastomer properties. If a total of three specimens fail then the batch will be rejected.

Figure 2.2.1 Cured elastomer properties