JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 42

FEATURE “Marine” surface reinforcements were developed and tested to hide the fibre print-through caused by underlying layers. Although resin shrinkage is the main reason for fibre print-through, the reinforcements also play a major role. To optimise mechanical properties, manufacturers often favour unidirectional or biaxial reinforcements which have good mechanical properties but show insufficient cosmetic qualities compared to chopped strand mats (CSM). The smoother the reinforcements, the better the laminate surface. However, a smooth fabric doesn’t always have the best handling characteristics, which means a compromise must be sought. An ordinary surface veil is merely compressed against the mould surface by the vacuum, having no significant contribution to surface quality. Figure 3 shows the influence of the lamination method and reinforcement type on surface quality. Adding ±45° NCF layers behind two CSM layers already impairs surface quality in hand lay-up. In vacuum infusion, the same reinforcements give really poor results. Replacing CSM with tailored surface reinforcements provides some improvement. An additional layer of barrier coat is needed to produce a surface quality comparable to hand lay-up. g…/… Surface quality in vacuum infusion temperature for 24 hours, and then post-cured at 40°C for 16 hours. This is equivalent to a laminate that has been allowed to cure for a long time at room temperature. Finally, in order to make sure that the laminates were fully cured, they were kept at 80°C for 16 hours. After each ageing step, the laminates were scanned with the MicroProf profilometer. To prove that this ageing method was realistic, some laminates were post-cured in a real outdoor environment for a month and then compared to those aged in the laboratory test chamber. The results showed that changes in surface parameters were similar in both cases. Resin comparison Resin shrinkage is the main cause of fibre print-through on a laminate surface. Shrinkage itself is dependent on the resin type, styrene content, etc. To determine the differences between resins, a series of infusion laminates was produced with selected marinegrade resins from Ashland. Each laminate used the same reinforcement and the processing variables were kept as constant as possible. Orthophthalic polyester (UP), new-generation dicyclopentadiene (DCPD) and AME® premium low-shrinkage vinyl ester (VE) resins were used. Out of curiosity, a new-generation lowprofile (LP) resin, Aropol® NLN 71500, was also included in the test, although LP resins cannot be used in all marine applications. Each laminate was aged in a laboratory test chamber as described before. After each ageing step, surface quality was measured with the MicroProf profilometer. Fig.3: Influence of various reinforcement types and lamination methods on surface quality (similar reinforcements are used in 2nd and 5th column). Different surface quality options – Skin coat & barrier coat To get a smooth surface with vacuum infusion, some sort of surface improving layer is still needed to prevent fibre print-through. Today, the majority of boat builders using vacuum infusion rely on a skin coat. Normally, a skin coat consists of a few layers of CSM with a high-quality, low-shrink resin. In addition to surface quality aspects, a skin coat also improves hydrolytic stability and ensures good bonding between the gelcoat and the laminate itself. In case of large parts, a skin coat provides more working time to put the reinforcements into the mould before starting the infusion. Over the years, skin coats have become so common that they have practically become part of the vacuum infusion process. A barrier coat is an additional layer applied behind the gelcoat to protect the laminate from hydrolysis. High-quality barrier coats are typically vinylester-based so as to achieve the best properties. In terms of application, barrier coats are reinforcement-free so they can be sprayed onto the mould. Barrier coats also proved to prevent fibre print-through effectively, which makes them a noteworthy alternative to skin coats as a surface improving layer. To determine the influence of skin and barrier coats on the final Fig.2: Different resins showed different surface quality properties. The laminates were made without using a surface improving layer (skin or barrier coat). The results clearly showed that there were big differences between resins. Not surprisingly, traditional orthophthalic resin showed the poorest surface quality characteristics. The difference with the DCPD and AME resins was obvious, due to the optimized cure profile and lower styrene content of these resins. In general, DCPD and AME showed similar behaviour. As expected, the Aropol NLN 71500 LP resin had the best surface finish. Reinforcement comparison The reinforcement packages used in these tests correspond to a sandwich skin thickness requirement for a 10 m motor boat; i.e. an approx. 3.5 mm thick laminate layer consisting of various ±45° and/or 0°/90° non-crimp stitched multiaxial fabrics (NCF). Special JEC Composites Magazine / No43 September 2008

JEC COMPOSITES MAGAZINE - Issue #43 - September 2008

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #43 - September 2008

Cover
Editorial
Market Place
Advertisers
CONTENTS
NEWS WORLDWIDE
- Companies
 - Agenda of events
 - Innovations
 - Equipment: Rapid prototyping
BUSINESS
 - Market survey
 - Niche market
 - Human capital
FEATURE - MARINE
 - Design
 - Modelling
 - Core materials
 - Prepreg
 - Natural fibre core
 - Sandwich structure
 - Gelcoat
 - Infusion
 - Application
USERS' PLATFORM
 - Composites in the world
 - Applications
KNOW-HOW
 - Materials
 - Manufacturing
Special JEC Composite Asia
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - Cover
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 2
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - Editorial
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - Market Place
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - Advertisers
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - CONTENTS
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 7
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - - Companies
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 9
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 10
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 11
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 12
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 13
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 -  - Agenda of events
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 15
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 -  - Innovations
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 17
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 -  - Equipment: Rapid prototyping
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - BUSINESS
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 -  - Market survey
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 21
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 22
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 -  - Human capital
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 24
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - FEATURE - MARINE
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 -  - Design
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 27
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 28
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 29
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 -  - Modelling
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 31
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 32
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 -  - Core materials
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 34
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 -  - Prepreg
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 -  - Natural fibre core
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 -  - Sandwich structure
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 38
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 -  - Gelcoat
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 40
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 -  - Infusion
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 42
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 43
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 -  - Application
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 45
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 46
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - USERS' PLATFORM
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 -  - Composites in the world
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 49
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 -  - Applications
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 51
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 52
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 53
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 54
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - KNOW-HOW
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 -  - Materials
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 57
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 58
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 59
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 60
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 61
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 -  - Manufacturing
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 63
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 64
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - Special JEC Composite Asia
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - II
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - III
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - IV
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - V
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - VI
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - VII
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - VIII
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - IX
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - X
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 75
JEC COMPOSITES MAGAZINE - Issue #43 - September 2008 - 76
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