Section 4 FRP Material and Moulding

401. General

1. The requirements in this section are applied to FRP materials and moulding used for hull con-

struction of recreational crafts. However,

are to be in accordance with the related

the requirements other than those specified in this section

requirements in Pt 2 of Rules for the Classification of

Steel Ships and Rules for the Classification for FRP ships.

2. Resins, gelcoats, fibre reinforcement, core for sandwich structure (Expanded plastics foam and End-grain balsa) and core for moulding used for FRP raw materials are to be approved by Society in accordance with the requirement of Guidance for Approval of Manufacturing Process and Type Approval, Etc.

3. Type Approval for FRP materials other than those specified in this section may be applied to rec- ognized Standards. Where deemed appropriate by the Society, National Standards, internationally recognized Codes or Standards considered as equivalent for those may be applied instead of re- quirements of this Guidance.

402. FRP Material

1. Reinforcement fibres

(1) The reinforcement used as a reference for this chapter shall be E-glass in accordance with ISO 2078. Other types of glass fibres may be used if the minimum properties of E-glass are met or surpassed and the laminate itself is of equal or higher mechanical property.

(2) The finish and binder of glass fibres shall be compatible with the matrix material used.

(3) Fibres made of material other than glass may be used, provided that their properties are suitable for the intended purpose.

(4) The material upon delivery complies with Table 3.5.

2. Resin

(1) Properties

The properties of liquid gelcoat, topcoat and laminating resins shall comply with the require- ments of Table 3.6, as applicable.

(2) Gelcoat resins

(A) Gelcoat base resins when cured shall meet the requirements of Type A in Table 3.7.

(B) For specific applications, in order to achieve superior properties as to elongation and/or re- duced water absorption, resins used for gelcoats and skin coats may deviate as to their min- imum properties from the requirements of Type A resin in Table 3.7.

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Table 3.5 Properties of fibre reinforcement

Table 3.6 Properties of liquid resins

Table 3.7 Properties of cured resins (after a postcure schedule of 24h at 50℃)

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(3) Topcoat resins

The formulation of a topcoat resin as to its physical properties shall consider the specific appli- cations for which it is intended and shall meet the respective requirements for Type A, B or C, for instance

(A) exposure to weathering;

(B) oily bilge water;

(C) tack-free surface only;

(D) suitability as a paint.

(4) Laminating resins

Laminating resins, including resin blends with permissible amounts of fillers and other additives when cured shall meet the respective requirements specified in Table 3.7.

(5) Fillers, additives

Quantities and types of fillers and/or additives shall allow sufficient wet out of reinforcement fi- bres within the resin manufacturer's specified gel time.

(6) Catalysts, accelerators

The use of catalysts and accelerators shall be as specified or recommended by the resin manufacturer.

(7) Declaration

(A) The resin manufacturer shall declare in writing that the material upon delivery complies with

Tables 3.6 and 3.7 appropriate to the manufacturer's specified Type A, B or C resin.

(B) If the resin manufacturer claims for exemption according to Table 3.7, i.e. that the require-

ments are not applicable to resins used in the formulations of fillers and putties, he shall state the mechanical properties achieved and shall provide information on the intended appli- cation of the resin.

(C) The manufacturer of the resin, catalyst, accelerator, filler or other substances used in the laminate shall each provide written information on

(a) the compatibility or incompatibility (if known) of the material supplied with other mate-

rials used in the laminate;

(b) the shelf life of the material;

(c)

the specific requirements concerning storage;

(d) the specific requirements concerning use.

(D) The boat manufacturer shall keep this information with the documentation established for the small craft.

3. FRP laminate

(1) The mechanical properties of the reference laminate as listed in Table 3.8 shall be achieved by any manufacturing process.

Table 3.8 Minimum mechanical properties of reference laminate

(2) The resin manufacturer shall declare in writing that the mechanical properties of Table 3.8 are capable of being fulfilled. The resin manufacturer shall provide detailed information with respect to other substances (e.g. catalyst, accelerator, fillers, additives, etc.) used in the fabrication proc- ess of the reference laminate.

4. Core for sandwich structure

(1) Structural requirements

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(A) Core materials for sandwich construction of small craft shall only be used if the following requirements of the final structure are fulfilled. The material shall have adequate properties to enable the sandwich structure to fulfil the requirements specified in Ch 4 for a normal service life in a marine environment, with special regard to

(a) in-plane forces, acting in the direction of the sandwich layers, e.g. tension, compression, shear;

(b) out-of-plane forces, acting transversely to the sandwich layers, e.g. compression, tension, shear.

(B) Fatigue performance must be considered when choosing the core material.

(2) General requirements

(A) Core materials shall have stable mechanical properties consistent with the designated use of the craft.

(B) Resin applied to the core material or its protective sheathing/coating shall be compatible with its surface.

(C) Core materials forming part of a sandwich structure shall

(a) limit the penetration of water beyond the area of a possible fracture of the skin laminate. This requirement does not apply for core materials that consist of a three-di- mensional open structure bonded to both skin laminates, e.g. honeycomb or three-dimen- sional fabrics.

(b) not emit significant amounts of gases that would compromise the bond or laminate.

(D) Core materials shall be capable of transferring the shear loads specified in Ch 4.

(E) The core material manufacturer shall provide written information on the mechanical and oth- er properties relevant for the intended application, as well as their variation in temperature and thermal limit of application where relevant.

(F) Where the core material used for structural parts may limit the mechanical properties of the sandwich panel due to extreme thermal conditions, the temperature range for safe operation of the craft shall be stated in the owner’ manual.

(3) End-grain balsa

(A) Where used as a structural core material of the hull, end-grain balsa wood shall fulfil the following requirements.

(a) be free from living organisms that may cause degradation when enclosed in a boat structure sandwich panel;

(b) have been homogenized;

(c)

have an average moisture content of 12 % to 15 %, when packaged.

(B) The mechanical properties as delivered shall comply with Grade I or II of Table 3.9.

(4) Special requirement for Expanded foam

(A) Expanded foam plastics used in structural sandwich cores of the craft shall be of a closed cell type.

(B) The mechanical properties of PVC (polyvinyl chloride) and SAN (styrene acrylic nitrile)

type foam cores, intended to be used in the structural laminate of hull, deck and first tier of the superstructure, if this is open to the atmosphere, shall at least comply with the prop- erties of Grade I of Table 3.10.

(C) The mechanical properties as delivered, intended to be used for other parts of the craft, shall comply at least with the properties of Grade II of Table 3.10.

5. Embedded materials—inserts

(1) The properties of expansion and contraction of inserts shall be similar to those of the laminate so that the overall performance of the structural laminate is not impaired.

(2) Embedded plywood shall be of the waterproof and boilproof type and shall have a surface that bonds easily to the resin or adhesive. Solid timber inserts between layers of laminate are not

recommended.

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Table 3.9 Minimum mechanical properties of end-grain balsa wood as delivered

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Table 3.10 Minimum mechanical properties of foam core materials as delivered

403. Workshop conditions

1. General

(1) The buildings used for production and storage shall be of suitable construction, provide the environment specified by the material manufacturer or supplier.

(2) To minimize contamination or impairment of the laminate, the production area

and equipped to shall be separate

from the storage area and, wherever practicable, the various manufacturing processes shall be carried out in separate sections.

(3) The workshop and equipment shall

stantially free from debris, surplus duction process.

be properly maintained and kept in a clean condition, sub- material, and equipment that is not essential for the pro-

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2. Temperature and humidity

(1) Where a conventional manual lay-up or spray-up process is used, the moulding shop temperature shall be maintained within the limits specified by the resin manufacturer during lay-up and cur- ing periods.

(2) Should the temperature vary outside the specified limits, the boat builder shall establish with the resin manufacturer that the resulting laminate will meet the requirements upon which scantlings

and design are based.

3. Ventilation

(1) Adequate ventilation shall be provided in the laminating area, in order to minimize accumulation of monomer fumes in the mould.

(2) The ventilation shall not significantly reduce the surface temperature of the mould or laminate.

(3) The design of the ventilation system shall take account of the size of the laminating shop, pos- sible subdivision and the amount of resin under cure.

(4) The ventilation arrangements shall not cause excessive evaporation of the resin monomer.

(5) Precautions shall be taken to ensure freedom from draughts.

4. Dust control

Provisions shall be made to minimize harmful accumulation of dust on moulds and laminates.

5. Illumination

Provisions shall be made to avoid any harmful effects on the resin cure due to direct sunlight or artificial lighting.

404.

Material storage and handling

1. General requirements

(1) Storage areas shall be arranged and equipped in such a way that the material manufacturer’ re- quirements for storage and handling can be followed.

(2) The procedures for the reception, verification against certificates of conformity, storage and han-

dling of materials shall be detailed in the conformity assurance procedures provided by the boat builder (see clause 10) to ensure that the materials suffer no contamination or degradation and

carry adequate identification at all times.

(3) Storage shall be arranged so that wherever possible materials are used in order of receipt.

(4) Structural parts shall be manufactured from materials that have not passed the material manu- facturers’date of expiry.

(5) Materials found to be defective or not in compliance with the specifications of raw-material

supplier(s) shall be rejected unless treated in accordance with the conformity assurance proce- dure, provided by the boat builder.

(6) Unused resin and ancillary materials exposed to the workshop atmosphere shall not be returned

to the parent stock or bulk storage.

2. Resin

(1) Resins shall be stored under controlled conditions in accordance with the resin manufacturer's requirements.

(2) Where a resin contains an ingredient that can settle within the resin system, it is the builder's responsibility to ensure that the resin manufacturer's recommendations for mixing and condition-

ing are complied with prior to use.

3. Catalysts and accelerators

Catalysts and accelerators shall be stored according to the material manufacturer's requirements.

4. Fillers and additives

Fillers and additives used in the moulding process shall be stored in closed containers to protect them from dust and humidity.

5. Reinforcing and core materials

Reinforcing and core materials shall be stored in clean and dry conditions, in accordance with the

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material manufacturer's recommendations.

405. Moulds

1. Construction

(1) Moulds shall be constructed of a suitable material and adequately stiffened to maintain their shape and fairness of form.

(2) The materials used in the construction of moulds shall not adversely affect the resin cure.

2. Preparation

(1) Moulds shall be cleaned, dried and in place so that they stabilize at the workshop temperature before the release agent is applied.

(2) The release agent shall be compatible with the mould surface, the resins applied in the laminat-

ing process and with mould release films used previously. Release agents containing silicon shall not be used.

406. Resin preparation

1. The requirements of the resin manufacturer shall be followed.

2. Where blended resins are used, test specimen(s) shall be made to ensure that the blended resin is suitable for the laminating process.

3. Where the boat builder wishes to modify resin with additives outside the resin manufacturer’ speci- fication, the boat builder shall conduct tests to verify compliance with Table 3.7.

407. Laminating process

1. General

(1) The resins are to be scrubbed by rollers till they are permeated completely. In the laminations for structures, the glass/resins ratio is to be the minimum quantities of the resins to permeate the glass completely. In the chopped strand mat moulded by the manual lay-up process, the weight of the glass/resins is to be 2.5:1 to 3:1.

(2) The hull lamination and other hull structural members are to be tested in glass fiber content ra- tio, aperture content ratio, hardening degree and mechanical strength etc. if it is necessary by surveyor.

(3) The laminations are to be free from defects such as blister, delamination, excessive resin etc.

(4) The overlapping breadths at butts and seams of mats which are composed of reinforcement layer are not to be less than 40 mm. The centre lines of overlaps of two adjacent plies are not be less than 100 mm apart from each other.

(5) In case where heavy mats and fibers are used, special attention is to be taken to permeate completely.

(6) When the dough materials with resin and glass fiber are used to increase the thickness of lami-

nation, they are to be same with main lamination. And the content of fiberglass is not to less than 25 % of resin and the length of fiberglass is not to be less than 25 mm.

(7) Where thickness of lamination are shifted, it is changed slowly and gradually. The change

weight for the hull lamination is not to be more than 1200 g per 25 mm as weight of glass ber reinforcement.

2. Manual lay-up

be

of fi-

(1) The material type and unit weight of the first fibre reinforcement layer shall be chosen to pro- vide for adequate penetration of the reinforcement layer by the resin system used and reduce the effect of hydrolytic attack.

(2) The lay-up sequence and degree of resin manufacturer's recommendation. the surface shall be treated.

(3) Moulds shall be arranged or access

resin cure between plies shall be in accordance with the Where the degree of cure exceeds these recommendations,

provided so that each part of the mould can be reached

with the tools used to ensure consolidation and de-aeration of the laminate during lay-up.

3. Spray lay-up

(1) Spray lay-up of resin and/or reinforcement fibres shall be limited to applications where, in gen-

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eral, a specified even thickness of the sprayed laminate can be achieved. Consideration given to

- exothermic heat by excessive wet laminate thickness,

- sagging or drainage of the laminate, and

- de-aereation

(2) The weight of glass reinforcement to be deposited between resin/glass consolidation upon the complexity of the mould. In general, this shall not be more than 1,150 gĤmË

shall be

depends of glass

fibres, unless it can be demonstrated that a satisfactory laminate can be achieved with a greater

glass reinforcement weight.

(3) The uniformity of the laminate and glass content shall be checked at regular intervals.

(4) Where the back-up layer behind the gelcoat is sprayed-up, the type and length of the fibres shall ensure that no wicking effect can occur.

(5) The spray equipment shall be calibrated and shall be checked for the desired setting for the res- in/catalyst and resin/reinforcement fibre ratios at the beginning of each working day.

(6) To ensure that the lay-up is within tolerances, the settings shall be monitored.

4. Closed moulding

When closed moulding is applied, the system shall be designed to ensure the correct distribution of resin in the laminate.

5. Pre-impregnated laminates

Pre-impregnated laminates shall be stored, used and cured in accordance with the material manu- facturer’ requirements.

408.

Surface coating

1. Coating material

(1) Gelcoat or another suitable coating, which may be the laminating resin when designed for this purpose, shall be applied to provide some protection from solar radiation, hydrolytic attack and abrasion.

(2) Where gelcoat is used, the first layer of reinforcement shall be applied according to the resin manufacturer's specification and as soon as the gelcoat has adequately cured.

2. Spray surface coating

The spray equipment shall be calibrated and shall be checked for the desired settings for the res- in/catalyst ratios and the spray pattern at the beginning of each working day or prior to the start of single-part work to ensure consistent application.

409.

Manufacturing requirements, sandwich construction

1. Sandwich construction using female moulds

(1) Core surface cavities and other irregularities shall be removed or coated with filler, resin or sandwich adhesive according to the material manufacturer’ specification and depending on the following skin lay-up. When using scored core material, a sufficient amount of resin or adhesive shall be used in the bond to fill the gaps.

(2) When bonding core material to a wet laminate, sufficient resin shall be in or on the laminate to achieve a bond between the laminate and core material without resin deficiency of the laminate.

(3) The materials shall be kept in contact while curing to ensure a structurally sufficient bond and

to avoid air entrapment.

(4) Deviations from these procedures may be made, provided that the structural requirements of

4 are met.

2. Sandwich construction with male moulds

(1) Joints, scores and voids in the core material shall be filled or fixed to each other before skin laminate is applied.

(2) When laying the core material, it shall not be bent or deformed to such an extent that properties of the core are adversely affected.

(3) Irregularities on the core surface and the joints shall be removed.

Ch

the the

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(4) The core surface shall be primed where required before the laminate is applied.

410. Laminate curing

1. Open-mould process

(1) The laminate cure schedule shall follow the resin manufacturer's requirements and shall be documented.

(2) The curing schedule for sandwich laminates shall take into account the thermal influence of the

core material and the possible slower initiation of the cure due to thin laminates.

(3) If the resin requires higher post-cure temperatures than ambient temperature, this process shall be documented.

(4) Post-curing at an elevated temperature shall not commence until the laminate has stabilized.

(5) The post-cure temperature shall be compatible with the temperature limits of the release agent and shall not adversely effect the gelcoat, the single skin or sandwich laminate.

2. Closed-mould process

The curing schedule for the closed-mould technique shall take into account the thermal influence of material, mass and construction of the mould.

411. Bonding

1. The required surface treatment for the laminate subject to the bonding are to be in accordance with manufacturer's specification.

2. If a laminate subject to secondary bonding has cured for more than 5 days the surface should be ground. If resin containing wax is used grinding is required if the curing time exceeds 24 hours.

3. If peel strips are used in the bonding surface the required surface treatment may be dispensed with.

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