Section 28 Materials of Reinforced Plastics

2801. Application

The requirements of this Section apply to tests and inspections for the type approval of the raw materials (reinforcements, thermosetting resins and core materials for sandwich construction) to be used for FRP ships conforming to the requirements of Pt 2, Ch 2, Annex 2-8 of the Guidance relating to the Rules for Classification of Steel Ships. Ch 3, Sec 2 of the Rules for Classification of Fibreglass Reinforced Plastics Ships and Pt 3, Ch 5, Sec 2 of the Rules and Guidance for the Classification of High Speed and Light Crafts.

2802. Data to be submitted

The following reference data are to be submitted to the Society in addition to those specified in

102.

1. Thermosetting resins

The data listed in Table 3.28.1 is to be provided by the manufacturer for each thermosetting resin.

Table 3.28.1 Data requirements for thermosetting resins

2. Reinforcements

The following data is to be provided, where applicable, for each type

(1) Reinforcement type.

(2) Fibre type for each direction.

(3) Fibre tex value.

(4) Fibre finish and/or treatment.

(5) Yarn count in each direction.

(6) Width of manufactured reinforcement.

(7) Weight per unit area of manufactured reinforcement.

(8) Weight per linear metre of manufactured reinforcement.

(9) Compatibility (e.g. suitable for polyesters, epoxides, etc.).

of reinforcement:

(10) Constructional stitching - details of yarn, specific gravity, type, frequency and direction.

(11) Weave type.

(12) Binder type and content.

(14) Density of the fibre material.

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3. Core materials

The following data is to be provided for each type of core material:

(1) Type of material.

(2) Density.

(3) Description (block, scrim mounted, grooved).

(4) Thickness and tolerance.

(5) Sheet/block dimensions.

(6) Surface treatment.

(7) full application procedure for use of the product.

2803. Type tests

The test items and test methods are to comply with the following requirements and the Flame spread (Fire durability) test in Table 3.16.1, 1603. of the Guidance as necessary.

1. Testing procedures

(1) General

(A) The test laboratory is to equip the test facilities so that they can perform the testing in ac- cordance with the requirements in this Section and are to be recognized by the Society

Alternatively, testing may be carried out by the manufacturer subject to these tests being

witnessed by the Surveyor.

(B) The accuracy of test machines is to be within ±1 % and test machines are to be recalibrated at approximately annual intervals. A record of all calibrations is to be kept available in the

test laboratory.

(2) Preparation of test samples

(A) Samples of thermosetting resins are to be prepared using the curing system recommended by the manufacturer and identical with that used for the finished product.

(B) The post curing conditions for samples of thermosetting resins are to be as recommended by the manufacturer and identical with those used for the finished product.

(C) Where curing of the product is intended to take place at room temperature, the sample is to be allowed to cure at room temperature (18 to 21 °C) for 24 hours followed by a post-cure

at 40 °C for 16 hours.

(3) Preparation of test specimens

(A) The test specimen is to be prepared in accordance with the appropriate ISO standard and the requirements of this Section.

(B) Precautions are to be taken during machining to ensure that the temperature rise in the specimen is kept to a minimum.

(4) Testing

(A) Strain measurement are to be made by the use of a suitable extensometer or strain gauge.

(B) The number of test specimens from each sample to be tested is to be in accordance with

the ISO standard. For mechanical testing this is five.

(C) If a test specimen fails because of faulty preparation or incorrect operation of the testing machine it is to be discarded and replaced by a new specimen.

(D) If the deviation of one result in a group of five exceeds the mean by more than two stand-

ard deviations, that result is to be discarded and one further specimen tested.

(5) Reporting of results

(A) All load/displacement graphs and tabulated results are to be reported, including mean values and the calculated standard deviation.

(B) Full details of the sample and specimen preparation are to be provided including (where ap-

plicable):

(a) Catalyst/accelerator or curing agent types and mix ratio.

(b) Weights of resins, and/or reinforcements used.

(c) Casting/laminate dimensions.

(d) Number of layers of reinforcement used.

(e) Curing/post-curing conditions.

2. Thermosetting resins

(1) Cast samples are to be prepared in accordance with the manufacturer's recommendations and are to be cured and post-cured in a manner consistent with the intended use. Where postcure con-

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ditions equivalent to ambient-cure conditions apply, see 1 (2) (B) and (C).

(2) The curing system used and the ratio of curing agent (or catalyst) to resin are to be recorded.

(3) The following are to be determined using these samples:

(A) Tensile strength (stress at maximum load) and stress at break.

(B) Tensile strain at maximum load.

(C) Tensile secant modulus at 0.5 per cent and 0.25 per cent strain respectively.

(D) Temperature of deflection under load.

(E) Barcol hardness.

(F) water absorption.

(G) Volume shrinkage after cure.

(H) Specific gravity of cast resin.

(4) For gel coat resins the stress at break and modulus of elasticity in flexure are to be determined.

(5) Test methods and acceptance criteria for cast thermosetting

3.28.2.

resins are to comply with Table

Table 3.28.2 Tests on cast thermosetting resin specimens

3. Reinforcements

(1) Tests of the mechanical properties are to be made on laminate ment and 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 laminate not less than 4 mm thick;

samples containing the reinforce- laid with parallel ply to give a

(C) the weights of resin and reinforcement used are to be recorded together with the measured

thickness of the laminate, including the measured weight per unit area of the reinforcement used;

(D) for glass reinforcements, the glass/resin ratios, by weight, as shown in Table 3.28.3 are to be used;

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Table 3.28.3 Glass fraction by weight for different reinforcement types

(E) for reinforcement type other than glass, a fibre volume fraction, as shown in is to be used.

Table 3.28.4,

Table 3.28.4 Fibre fraction by volume for different reinforcement types

(2) Rovings intended for filament winding are to be tested as unidirectional rovings.

(3) The laminate is to be tested in air in the directions indicated by Table 3.28.5.

Table 3.28.5 Fibre orientations in reinforced test specimens

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(4) The following tests are to be made on the samples:

(A) Tensile strength (stress at maximum load).

(B) Tensile strain at break.

(C) Tensile secant modulus at 0.5 per cent and 0.25 per cent strain respectively.

(D) Compressive strength (stress at maximum load).

(E) Compressive modulus.

(F) Flexural strength (stress at maximum load).

(G) Modulus of elasticity in flexure.

(H) Apparent interlaminar shear.

(I) Fibre content.

(J) water absorption.

(5) Additionally, tests in (4) (c) and (f) are to be repeated, in one direction only, after immersion in fresh water at 35 °C for 28 days with the exception of 2.4.4(k).

(6) The test methods and acceptance criteria applied to laminate specimens of reinforcement comply with Table 3.28.6.

are to

Table 3.28.6 Test methods and acceptance criteria of reinforcement specimens

4. Core materials

(1) Initially the core shear strength and modulus are to be determined by ISO 1922–981 or ASTM C273. Test sandwich panels are then to be prepared and subjected to four-point flexural tests to determine the apparent shear properties according to ASTM C393 (short beam) at two repre- sentative thicknesses (i.e. 15 mm and 30 mm). Testing is to be carried out at ambient temper- ature and at 70 °C. The following requirements are to be observed:

(A) Each skin is to be identical and have a thickness not greater than 21 per cent of the nomi- nal core thickness. For hand laid constructions, each skin is to comprise a lightweight chop- ped strand mat reinforcement (300 g m ) consolidated at a glass content, by weight, of 0,3 against the core, plus the required number of woven reinforcements consolidated, using an isophthalic polyester resin, to give a minimum glass content, by weight, of 0,5.

(B) The method of construction of the sandwich laminate is to reflect the core material manu- facturer’ instructions for use, i.e. application of bonding paste, surface primer or any other recommended system.

(C) Curing conditions are to be in accordance with 1 (2), (B) and (C).

(D) The dimensions of the test samples should be based on the requirements of ASTM C393 Paragraph 5.1, and the ratio parameters as indicated in ASTM C393 Paragraph 5.2, using a proportional limit stress (F) for the woven roving skins of 130 N mm and a span (a2) of not less than 400 mm.

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(2) For each type of test sample the following data are to be reported, together with the submission of a representative test sample showing the mode of failure for each density of core material:

(A) Skin and core thickness, and core type and density.

(B) Resin/catalyst/accelerator ratio.

(C) Skin construction, including types and weight of reinforcements, resin(s), etc.

(D) Details of production method and curing conditions (temperature and times).

(E) Where additional preparation of the foam is involved, for example the use of primers or bonding pastes, full details are to be provided.

(F) Actual span between base supports for each type of test sample.

(3) Specific requirements for end-grain balsa

(A) The following tests are to be carried out on the virgin material, both parallel to and perpen- dicular to the grain. The density of the virgin material is also to be tested.

(a) Compressive strength (stress at maximum load).

(b) Compressive modulus of elasticity.

(c) Tensile strength (stress at maximum load).

(B) Where the balsa is mounted on a carrier material (e.g. scrim), any adhesive used is to be of a type compatible with the proposed resin system.

(C) The test methods and acceptance criteria for end-grain balsa are to comply with Table

3.28.7.

Table 3.28.7 Test methods and acceptance criteria of end-grain balsa

(4) Specific requirements for rigid foams (PVC, Polyurethane and other types)

(A) The following test are to be carried out for each type of foam:

(a) Density.

(b) Tensile strength (stress at maximum load).

(c) Tensile modulus of elasticity.

(d) Compressive strength (stress at maximum load).

(e) Compressive modulus of elasticity.

(B) Additionally the compressive properties (see (A), (d) and (e)) are to be determined at a minimum of five points over the temperature range ambient to maximum recommended serv- ice or 70 °C, whichever is the greater.

(C) The test methods and acceptance criteria for rigid foams are to comply with Table 3.28.7.

2804. The test for each FRP ship is to be conducted in accordance with the requirements in Ch 3, Sec 3 of Rules for Classification of FRP Ships.

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