Are we letting things slip?

Are we letting things slip? In several recent assignments as a composites consultant, problems have been seen with quality in mouldings in the commercial composites sector. Largely in the form of panels for railway, architectural and similar applications, the method of construction has usually been hand laminating or spray deposition with the occasional resin transfer moulded (RTM) component. Whilst there is doubtless great growth potential in the structural side of our industry and higher capital investment processes serve that sector most readily, it must be agreed that, in volume terms, the commercial sector will have the upper hand for many years yet. For this reason alone, we should take the utmost care in assuring the quality of the products which we manufacture. The introduction which most engineers and specifiers have to composite materials is through commercial market products made of ftbreglass. If these are seen by users and observers to fail by warping, cracking or whatever, which of those people, who happens to be responsible for specifying the next major road bridge are ever going to consider composites? As an excuse, the cry of the price was too low will not do. The failures under discussion have had nothing to do with price, simply lack of care, skill or adequate quality control. One common fault is poor reinforcement distribution. This can take the form of corners, edges or ribs which are resin rich, sometimes to the point of being glass-free! It is difficult to persuade a 450 g chopped strand mat to stay in a narrow rib so why not put rovings at the bottom of the rib or use a lighter mat at that point or even, dare it be suggested, fold a strip of cloth into the rib. The rib will then have the reinforcement it needs and the moulding the stiffness. It takes seconds longer but that should be in the price, unless those who make these errors actually base costs on a shoddy job. There is simply no excuse for the glass not going to the edge of a moulding. With handlay, it should go slightly beyond and be trimmed to ensure

Keinforccd

Plastics Lkcembcr

1995

uniform distribution. If the principal lay-down is by spray deposition, consider whether the chop length you are using will roll into tight corners. If it will not then spray a little resin in the difficult areas first and roll in rovings, cloth, etc. before the bulk of the spray up is made. Other items have suffered failure, or at the least distortion, when there appears to be no problem with the reinforcement. Relatively small differences in gel-coat thickness or mix formulation can be the reason for this type of problem. Gel-coat thickness is a matter of skill and training. However sloppy weighing out of resin into already dirty containers and the misuse of catalyst squeezies are still common sources of error. Wall mounted dosing units are available to eliminate this type of problem. These may be simply hand operated or air driven to dispense at the push of a button. They are available either for individual materials or to provide a measured volume of premixed resin and catalyst. A small investment will save reject mouldings, messy resin stordge areas, material wastage and, hence, money. It will also improve on the health and safety aspects of the shop. Quality is important to all industries but, for reasons unknown, our industry is often judged as a whole. One failure of a moulding, a discolouration or surface crazing in a panel are things which make a specifier swear never to use fibreglass again. If it were poor grade timber cracking, supposedly galvanized steelwork rusting or premature paint peeling the same specifier might swear never to use Bloggs & Sons again but he would use timber, galvanized steel and paint. Quality is not only about IS0 9000. That will trace the raw materials if there is a problem which is so attributable. It is, however, we who mix the chemicals, lay them together and create the finished material and moulding. If we do not do that with utmost care, we may not be doing it at all in certain market sectors. Ken L. Forsdyke Principal,

(H)W-3(,17/95/17.00~~;

1995,

Elsrvirr

Fortech

Science

Ltd