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Glass Reinforced Plastic Materials

In document Indian Coast Guard Ships (Page 43-48)

4.1 General

4.1.1 The requirements given in this section are based on the use of an unsaturated polyester resin system with glass fibre reinforcement and employing hand lay-up or spray lay-up contact moulding production techniques. Other types of resin systems and reinforcements may be accepted based on testing and approval in each individual case.

4.1.2 The following base materials used in the construction or repair of GRP Ships are to be approved in accordance with the approval procedure given in this sub-section and the requirements of sub-sections 4.3, 4.4 and 4.5, as relevant.

- Glass fibre reinforcements - Polyester resins

- Sandwich core materials - Sandwich adhesives.

4.1.3 Materials other than GRP, are to be of good quality, suitable for the purpose intended and where applicable, are to comply with the Rule requirements appropriate to the material. Where these materials are attached to, or encapsulated within the GRP construction, they are to be such as not to affect adversely the cure of plastic materials.

4.2 Procedure for approval of base materials

4.2.1 The following information is to be submitted by the manufacturer for each base material product for which the approval is sought.

a) Detailed specifications for each grade, giving Manufacturer’s Nominal Values (MNV) and corresponding acceptable tolerances.

b) An outline of the production process giving details of all important stages in production.

c) A brief description of the plant and equipments.

d) Details of systems employed for production and quality control.

e) Details of the systems used for the identification of raw materials, semi-finished and finished products.

f) The number and qualifications of all staff engaged in quality control duties.

g) Details of test equipment, testing procedures, stages at which tests are carried out by the Manufacturer and frequency of testing.

h) Manufacturer’s test results for a period of at least 3 months covering testing on at least 10 production batches.

The Manufacturer’s works and equipment are to be inspected to examine all aspects of production and quality control as per the above mentioned details and the actual testing for approval of product may commence only after they have been found satisfactory.

4.2.2 The base material products are to be tested in accordance with the recommended test methods given in 4.3, 4.4 and 4.5, as relevant. Other equivalent test methods may be individually considered. The test equipment used is to be kept in a satisfactory and accurate condition and calibrated annually. The tests are to be carried out by competent personnel and are generally to be

witnessed by Surveyors. In case of testing by reputed independent test house, the witnessing may be waived at the discretion of the attending Surveyor.

4.2.3 The test samples and specimens are to be prepared in accordance with the manufacturer’s recommendations and the relevant recommended test methods. When tests on GRP laminates are required, the laminates are to be moulded by the hand lay-up method at an angle of 45 deg. to the horizontal and under environmental conditions specified in Chapter 7, Section 2.

4.2.4 On the satisfactory completion of all testing a type approval certificate valid for a period of five years shall be issued which shall be subject to the conditions of approval given in 4.2.5 and 4.2.6 and satisfactory annual inspections as per 4.2.7. Any alteration in the composition of the product or in any of the production details which affect the quality may warrant new approval testing.

4.2.5 The type approval is given on the condition that the product material, when correctly examined will give test results reasonably close to the submitted properties. Should the properties of the base materials or those of well made laminates using these materials be found to deviate significantly from the submitted properties, or should the quality control procedures not be adhered to consistently, approval will be withdrawn.

4.2.6 Each delivery of raw materials is to be suitably marked with following details:

- Approval Certificate No. and date - Designation of product

- Batch No.

Properties to be tested for each delivery or batch to which the delivery belongs are specified in Tables 4.3.4, 4.4.2 and 4.5.4 (marked (D)). The values resulting from testing are to be recorded and made available for inspection.

4.2.7 Manufacturers’ works and quality control systems are to be subjected to annual inspection.

The scope of inspection and testing at the annual inspection is limited to ensuring that the conditions of approval given in 4.2.4 to 4.2.6 remain valid.

Quality control records and Manufacturer’s test results are to be made available to the Surveyor and random tests are to be carried out in the Surveyors’ presence to adequately demonstrate that the consistency of the approved grade is satisfactorily maintained.

4.3 Glass fibre reinforcements

4.3.1 The Rule requirements in respect of the following types of glass fibre reinforcements are given in this section.

- Chopped strand mat - Unidirectional - Woven roving - Woven cloth

Other types of glass fibre reinforcements will be individually considered.

4.3.2 Reinforcement features

The following details are to be provided as applicable, for each type of reinforcements:

a) Reinforcement type b) Fibre tex value

c) Fibre finish and/or treatment d) Yarn count in each direction

e) Width of manufactured reinforcement

f) Weight per unit area of manufactured reinforcement

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g) Weight per linear metre of manufactured reinforcement h) Compatibility (e.g. suitable for polyesters, epoxides, etc)

i) Constructional stitching (details of yarn, type, frequency and direction) j) Weave type

k) Binder type and content.

4.3.3 The glass fibre reinforcements are to be manufactured from low-alkali borosilicate “E” glass. A chemical analysis is to be carried out and the chemical composition (%) is to comply with the following requirements:

SiO2 CaO AL2O3 B2O3 MgO Na2O + K2O 52-56 16-

25

12-16 6-12 0-6 0-1

Binders where used are to be soluble polyester resin. Sizes and finishes are to be of the silane type, and are to be compatible with the laminating resins.

4.3.4 The glass fibre reinforcements and laminates prepared from them are to be tested in accordance with Table 4.3.4 and are to comply with the requirements specified therein.

For the purpose of this approval testing, the laminates are to be prepared as follows:

a) An approved resin of suitable type is to be used.

b) A minimum of three layers of the reinforcement is to be laid with parallel ply to give a laminate not less than 4 mm thick.

c) The weights of resin and reinforcements used are to be recorded together with the measured thickness of the laminate.

d) The following glass/resin ratios by weight, are to be used:

Reinforcement type Glass fraction Chopped Strand-mat 0.3

Unidirectional 0.6

Woven Roving 0.5

Woven Cloth 0.5

The laminates are to be tested in air in the directions indicated below:

Type of reinforcement

Test orientation

Unidirectional 0o

Chopped Strand Mat any direction Woven Roving

Woven Cloth

0o and 90o 0o and 90o

4.4 Polyester resins 4.4.1 Scope

The Rule requirements in respect of the following unsaturated polyester resins suitable for lamination by hand lay-up are given in this section.

- Isophthalic polyester resins - Orthophthalic polyester resins.

It may be noted that orthophthalic polyester resins are not to be used in the main hull.

The resins are to have good wetting properties and are to cure satisfactorily under specified environmental conditions.

4.4.2 Properties

For each grade of resin to be approved, resin in liquid and cast conditions and the laminates prepared from it are to be tested in accordance with the Table 4.4.2 and are to comply with the requirements specified therein.

For the purpose of approval testing, the laminates are to be prepared in accordance with 4.3.4 using the resin under consideration and an approved chopped strand mat reinforcement. Where woven cloth having directional properties are used and /or where vacuum infusion process is used, the properties will be specially considered. The properties given in Table 4.3.4 is based on hand lay-up method of manufacture.

4.4.3 The resins to be approved for application in gelcoats are to satisfy the requirements for isophthalic polyester resin given in Table 4.4.2 for liquid and cast conditions. Testing of laminates prepared using the resins need not be carried out.

Table 4.3.4 : Properties for acceptance purposes - Glass fibre reinforcements

Property Required values Recommended Test Methods

(A) GLASS FIBRE REINFORCEMENTS

Moisture content (D) Max. 0.2% (max. 0.3% for emulsion bonded CSM)

ISO 3344

Av. weight per unit area (D) MNV ± 8% BS 3749

BS EN 14118

% max. variation in weight per unit area (D)

19% of MNV BS 3749

BS EN 14118

Loss on ignition (D) MNV* ISO/R 1887

Mat binder solubility (for CSM only)

MNV* BS EN 14118

Wet-out time MNV* BS EN 14118

(B) LAMINATES

Ultimate Tensile Strength Tensile Modulus

Subject to approval in each separate case

ISO 527-4 Ultimate Bending Strength

Bending Modulus - do -

ISO 178

Glass Content - do - ISO 1172

Notes:

MNV : Manufacturers Nominal Value (As given in the product specifications) D : To be tested for each delivery/batch

* : Tolerance limits are subject to approval in each separate case.

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Table 4.4.2 : Properties for acceptance purposes : Polyester resins

Property Required values Recommended Test

Method ISOPHTHALIC ORTHOPHTHALIC

(A) LIQUID RESIN

Density (D) MNV ISO 1675

Viscosity (D) MNV ± 20% ISO 2555 OR ISO

2884

Acid value (D) MNV ± 10% ISO 2114

Monomer content (D) MNV ± 10% ISO 3251

Gel time (D) MNV ± 20% ISO 2535

Shrinkage during cure (D)

MNV ISO 3521

(B) CAST RESIN

Density MNV MNV

Hardness (Barcol) 35 35 ASTM D2583

Heat deflection temp. 75 (°C) 62 (°C) ISO 75

Water absorption (mg) (28 days immersion)

80 (mg) max. 100 (mg) max. Method A ISO 62

Ultimate tensile strength

45 [N/mm2] 45 [N/mm2] ISO 527-4

Tensile modulus 3000 [N/mm2] 3000 [N/mm2] ISO 527-4 Elongation at fracture 2% (2.5% for gelcoat) 1.5%

Ultimate bending strength

80 [N/mm2] 80 [N/mm2] ISO 178

(C ) LAMINATE Ultimate tensile strength

85 [N/mm2] ISO 527-4

Tensile modulus 6500 [N/mm2] ISO 527-4

Ultimate bending strength

152 [N/mm2] ISO 178

Bending modulus 5206 [N/mm2] ISO 178

Glass content (by weight)

0.3 ISO 1172

Notes:

MNV : Manufacturer’s Nominal Value (as given on the product specifications) D : To be tested for each delivery/batch

4.5 Sandwich core materials

4.5.1 The Rule requirements in respect of the following core materials to be used in sandwich constructions are given in this section.

• Rigid expanded PVC foam

• Balsa wood.

Where plywood is proposed to be used as core, it is to be of a marine grade meeting the strength requirements of Chapter 6.

Other core materials such as honeycombs, etc., will be individually considered. Expanded polystyrene foam is attacked by the styrene in the polyester resin and is not recommended for use as core.

4.5.2 Rigid expanded PVC foams are to have closed-cell structure and be impervious to water, fuel and oils and are to be compatible with the polyester resin. The foam is not to shrink with time, the shrinkage strains if any, not exceeding the tolerances on linear dimensions.

4.5.3 Balsa wood is to be end-grain and to have moisture content not exceeding 12%. Where manufactured into formable sheets of small blocks, the open weave backing material and adhesive are to be compatible and soluble, respectively, with the polyester laminating resin.

4.5.4 The core materials and the sandwich panels prepared with the core material under consideration are to be tested in accordance with Table 4.5.4 and are to comply with the requirements specified therein. The skin laminates used in the construction of the sandwich panel are to be prepared from approved resin and CSM reinforcements.

Table 4.5.4 : Properties for acceptance purposes - Sandwich core materials

Property Required values Recommended Test Method

(A) CORE

Density [Kg/m3] (D) MNV + 15%

- 0%

ASTM C-271 specimen 1000 x 1000 x thickness of sheet [mm]

Compressive strength [N/mm2] (D)

0.7

0.53 (after 4 weeks immersion in salt water)

ISO 844 Compressive modulus [N/mm2] 30

22.5 (after 4 weeks immersion in salt water)

ISO 844

Shear strength [N/mm2] 0.69 ISO 1922

Shear modulus [N/mm2]

12 ISO 1922

Water absorption [Kg/m2] (1 week immersion in salt water)

1.5 max. ASTM C272

40 deg. C

Styrene resistance Resistance ISO 175

(B) SANDWICH PANEL

Shear strength [N/mm2] 0.69 Failure not to occur in bond between skins and core

ISO 1922

Shear modulus [N/mm2] 12 ISO 1922

Notes:

MNV : Manufacturer’s Nominal Value (as given in the product specification) D : To be tested for each delivery/batch.

In document Indian Coast Guard Ships (Page 43-48)