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Reinforced plastics — ever new 28th SPI Annual Conference
Conference report Washington DC, USA (February 6 - 9 , 1973) Reinforced
plastics -- ever new
28th SPI A n n u a l Conference
This year's Conference attracted some 2 000 delegates to hear at least some of the 100 papers given in 22 concurrent sessions during the four days of the meeting. This report tries to give an overall picture of the areas where research and development is most active, and which markets in composite materials currently appear most attractive in the USA. The conference covered 15 areas (see list of papers) and those areas which covered two or even three sessions are obviously the ones where companies consider that research and development will be most rewarding. Although there were specific sessions labelled 'Research and Development', every paper submitted involved either some research or development. The 'Research and Development' sessions, which will be dealt with first, tended to cover the more academic papers and were mostly submitted either by government laboratories, universities, or aviation laboratories. RESEARCH AND DEVELOPMENT
There has been a significant trend over recent years away from papers based purely or mainly on theoretical treatments of the behaviour of composite materials stressed in a variety of modes; although still largely based on a theoretical approach the papers tended to contain more experimental data for comparison with theory, and were directed to the more urgent areas where design data is necessary for expansion in the utilisation of composite materials. There seemed no doubt this year that the emotive term 'brittleness', or lack of toughness, is the main stumbling block to the increased use of high performance composites in highly stressed applications, especially in those areas where sudden failure could have catastrophic consequences. Much interest has been shown in the concept of toughening epoxide resins by the incorporation of rubber spherical particles, in particular the use of carboxyl terminated butadiene (ctbn) which, due to reaction between the carboxyl termination and the epoxide resin, results in good adhesion at the rubber sphere/resin interface. There is now good evidence that, using the 'in situ' formation of spheres of suitable diameter, ideally a bimodal distribution of spheres, some 1-5/am diameter, and others <1 000 A diameter, impressive improvements in fracture toughness and impact strength can be attained. No data were presented, however, on the improvements occasioned by the use of ctbn modified epoxide resins in composites, which was disappointing. Our own experience and the experience of others at the Conference was that the improvements achieved in the resin had not so far been realized in the composites. Papers on the toughness of composites were presented by Professor Outwater (17-A) and Professor Broutman
COMPOSITES. SEPTEMBER 1973
(17-B). The former's paper discussed the sources of energy dissipation during composite fracture and quantified these by considering the energetics of fibre debonding. Broutman's paper described experiments using an instrumented drop weight impact machine to measure the impact strength of carbon fibre composite. His findings, that increases in strength and energy absorption increase with increasing impact velocity, seem to agree with early results from work at Harwell by Hancox and Minty which involved the study of torsional impact at strain rates of up to 50 rad/s. Robert Simon (17-C) from the Naval Ordnance Laboratory made a plea for work on what he termed an 'energy threshold' to create damage in composites. His well written paper described the impacting of NOL carbon fibre composite rings and subsequent measuring of their residual compressive strength; a typical graph illustrating this threshold concept is shown in Fig. 1. His paper also illustrated that the incorporation of other high strength fibres of lower modulus, eg PRD 49, can uprate the threshold impact value of carbon fibre composites.
AEROSPACE AND HIGH PERFORMANCE COMPOSITES
Personally the most interesting paper in this session was that by E. E. Hardesty (15-D) of Goldsworthy Engineering Inc, a company well known in the rapidly expanding processing field known as 'pultrusion'. Conventionally pultruded composites are produced continuously in a wide variety of profiles such as rods, bars, tubes, box sectians, etc, and normally in straight lengths of up to 9 m (30 ft). Hardesty described Goldsworthy's latest innovation, equipment which will produce curved or circular composites again in a variety of profiles. A typical product is the production of large rings or hat sections for skin stiffening. This paper, and a later paper from the same organization dealing with the production of pultruded piping, emphasized
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the need for more effort in evolving processes for producing composites in a highly reprodticible and economic manner. The paper by Browning (15-A) of the Air Force Materials Laboratory, suggested that, whilst a variety of cast resin systems were not hydrolyticaUy unstable, water could act as a plasticizing agent and apparently disrupt the strong hydrogen bonding present in highly polar epoxide systems. As evidence, he tabled results which showed the reversability of the water absorption effect and the change in failure mode of dry and wet specimens. The results emphasized the need for more environmental studies allied to mechanical testing to produce more meaningful design data than that normally available at a single humidity or temperature. John Sturgeon (12-B) of RAE Farnborough presented a paper on the creep and fatigue of carbon composites in a tensile mode, which effectively indicated the excellent creep resistance in this mode; he did however point out a large variability in fatigue results which he attributed to the characteristics of the material. Other papers included acoustic emission studies on boron/ epoxide and graphite/epoxide composite rocket motor cases and the evaluation of graphite/epoxide composite materials for helicopter transmission housing. It is significant that an increasing number of papers on the high modulus fibres are now concerned with the manufacture of prototypes rather than purely devoted to testing techniques.
PROCESSING
Further illustrations of quickening interest in mass production or mechanization of processes for producing composite materials were papers by S. Sikes (22-A) of GRTL Company and H. H. Maihart and R. H. Reiter (22-C) of Kolosius GmbH Austria. Sikes' paper described the forming of swirl glass reinforced thermoplastic sheet on conventional metal stamping equipment. Cycles as short as 15-20 s are achievable where production volume affords automated feeding and part removal system. The Austrian paper was concerned with the economic and rapid production of large volume standing storage tanks. Basically the centrifugal casting equipment consists of a rotatable cylindrical mould which can achieve rotational speeds of 5 - 9 0 rpm which in the case of a 3½ m (11½ ft) diameter rotor would correspond to a maximum of 16 m/s (54 ft/s). The resin/glass depositor is fitted on a telescopic jib and other basic equipment includes supply tank, pump equipment, glass rovings stand, ancillary mechanical consolidation and the controls. There is an overhead travelling crane to enable the mould, which is split in the axial direction, to be opened for the removal of the completed tank. Production time for a silo of 99 m 3 (3 500 ft3), was given as 2% hours or approximately 3 silos/8 h shift. The author made a very good case for the choice of centrifugal method as opposed to filament winding techniques, which, due to higher glass fibre content, would give similar deflection with a thinner wall section and thus use less material.
230
His argument was that in the specific cases if silos and similar storage tanks, the high mechanical strengths achieved by filament winding are unnecessary, because in the calculation for wall thickness, static inside pressure is less important than in resistance to deformation due to wind pressure and silo-handling. HOUSING AND CONSTRUCTION
An ingenious method for providing emergency accommodation in disaster areas used the concept of converting a flexible fabric parachute into a rigid shell in the time between release and hitting the ground. The imaginative paper by Professor Benjamin (4-B) of the School of Architecture at the University of Kansas covered in some detail the problems associated with such a concept; these were, briefly, choice of a suitable resin system, type of parachute and the fabric used to construct it, the opening characteristics, method of impregnation, aerodynamic behaviour and, a very important factor, the need for a visual leaflet to convey to possibly illiterate people the correct use of the shelter. David Powell (4-E) of Polyplan, England, gave a very professional paper on 'New Contributions of FRP in the Construction Industry': he described the large scale application of reinforced plastic cladding panels at the Southbrook Comprehensive School and the extensive use of such panels, 2 7871 m 2 (300 000 ft2), in a redevelopment scheme for HMS Raleigh, the shore-based training establishment of the Royal Navy. REINFORCED THERMOPLASTICS, SHEET MOULDING COMPOUNDS, AND DOUGH MOULDING COMPOUNDS
These materials are competitors for supplying probably the largest potential markets in reinforced plastics, eg.the Transportation Industry. Two years ago there seemed to be a swing to reinforced thermoplastics for the car industry, but the sheet moulding compound advocates have come back with improved properties and processes and are again strong contenders in the market. Undoubtedly cost will be the prime consideration in determining which material is t'mally chosen, but other factors, eg specific stiffness, creep and impact resistance, will also influence the choice. Although 23 papers were delivered on these materials, the author found only one which seemed novel. This was a paper by D. F. Maine (5-A) of Fibreglass Canada on the use of mica as a reinforcement for thermoplastics. Mica has, of course, been used in plastics for a considerable time, but normally as a high quality filler to improve electrical properties. Maine pointed out that polymers reinforced with platelets can be treated in a manner similar to discontinuous short fibres and that if one makes similar assumptions to those used in short fibre theories, eg good bonding, sufficient aspect ratio, good distribution, and uses mica with a modulus of 172 x 103 MN/m 2 (25 x 106 psi) and tensile strengths as high as 3 100 MN/m 2 (450 000 psi), a reinforced polymer superior to a similar short glass fibre filled polymer would result. He als~J suggested that due to the plate-like nature of mica the strengths measured would be more truly isotropic than fibres, and illustrated this by a graph (Fig.2) which compares the
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By using rods of various aspect ratios and spheres of various diameters in packing experiments, he derived graphs which should optimize the packing of spheres and fibres in a polymeric matrix. His paper will be very useful as a guide to anyone involved in such areas of development, eg Idled thermoplastics and thermosets, sheet and bulk moulding compounds, and is well worth studying.
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particular his work with ceramic whiskers as reinforcements of materials. His paper this year was on a more mundane level, namely a consideration of the packing efficiency of fibres and spheres.
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A joint paper given by J. E. Hill of Great Lakes Research Corp and E. A. Pearson of Tillotson-Pearson Inc (20-B) described the use of wide tow carbon fibre/resin reinforcements of selected areas of a 14 m (46 ft) glass fibre/balsa core sandwich sailing sloop. Construction details of the stern, backbone-keel support skeg, and stern areas, which are those reinforced by carbon fibre, ~vere given in reasonable detail and obviously much effort had been spent in design to ensure that the reinforcement was used efficiently and economically. Dramatic weight savings were achieved. The total weight of carbon fibre/resin composite used was 23 kg (50 lb)
The properties he listed for mica filled nylon included 17.2 x 103 MN/m 2 (2.5 x 106 psi) modulus with approaching 96 MN/m 2 (14 000 psi) tensile strength (not included in the preprint) of the reinforcing effects in thermoset resins; these implied that mica merits serious consideration as a reinforcement for many polymers.
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RESINS, REINFORCEMENTS AND FILLERS
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Work reported on resins is usually almost totally confined to either polyesters or epoxides, and normally concerns such aspects as improving fire or corrosion resistance, or the use of additives to give lower shrink characteristics in the case of polyesters; this year was no exception and, in my view, nothing startling emerged.
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The same usually applies to reinforcement but in recent years we have had reports of carbon and boron fibres and PRD 49. This year, American Enka Company reported work on the effects of using ENCRON polyester fibre reinforcement in composite materials.
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C. C. McCorsley (3-C) presented the paper, which examined improvements in abrasion resistance, chemical resistance, and impact, by using various types of sandwich construction with layers of glass or terylene reinforced polyester resin. As one would expect from theory the best combination of flexural strength, flexural modulus, and impact came from a combination of glass woven rovings on the tensile and compressive axis, with layers of terylene fabric in the neutral plane as shown in Fig.3. Many papers in the past have described the effect of adding short glass fibres to polymers, in particular in thermoplastics, and in recent years interest has quickened in the use of spherical glass to confer rigidity and dimensional stability in polymers. Dr J. Milewski (3-F) of Esso Research Engineering Co is well known in the USA for his work on ceramics and in
COMPOSITES. SEPTEMBER 1973
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231
compared to 104 kg (230 lb) of unidirectional glass/ resin composite which would be necessary to achieve the same stiffness.
$17 000 000/ship in grp using either a pessimistic or optimistic cost estimate.
The sloop Fantasia has now completed one year's sailing and is in excellent condition having weathered two severe storms in the 1972 Bermuda-Newport race.
BATHROOM COMPONENTS
It is interesting to compare the paper by R. J. Scott and J. H. Sommella (14-C), of Gibbs and Cox Inc, which is a feasibility study of large glass reinforced cargo boats, typically 137 m (450 ft) long with a wide beam of 21 m (69 ft) and displacing 16 764 tonnes (16 500 long tons).
At present in the USA the use of composites in bathroom components has probably the largest growth rate in the building and construction area. In particular the concept of vacuum forming thermoplastic sheet and subsequently rigidizing with glass/resin reinforcement, first reported by V. Staynor in 1970, has become a very popular and economic way of forming composite materials.
The work, sponsored by the Ship Structures Committee of the National Research Council, is very detailed, and the conclusions state that a ship of this size is perfectly feasible, but its durability is questionable and not economically justified in direct competition with a steel vessel of equivalent capabilities. Fire resistance is also given as a major drawback under current US Coast Guard regulations.
The papers this year were concerned with ways of automating and speeding the process and also with drawing attention to the superiority of the thermoplastic component over traditional gel-coats under impact conditions; this philosophy appears to make good sense especially when one considers that vacuum forming/rigidizing processes are spreading to a number of other applications, eg sailing dinghies, building cladding panels, etc.
When the limitations set on the study are considered, however, the future looks promising. These limitations included:
Unlike the British Plastics Federation Conference the SPI has no formal dosing speeches, the delegates depart and prepare for another marathon in twelve months time.
(a)
The ship would be constructed from state of the art materials: local stiffening using carbon fibre composites was precluded.
(b)
Although the authors concede the possible development of a major breakthrough in fabrication of large GRP structures, they consider this will require a significant R and D effort requiring a great deal of time and money. They therefore assumed that hand lay-up technology would be used.
It is an exhausting Conference for participants, but is usually rewarding in spite of the normal quota of superficial and blatantly commercial papers. It is disappointing not to see more European delegates attending. Reading the rather bulky and lengthy reprints of the proceedings is a poor alternative to involvement in the sessions and discussions, and even more, out of session discussions with other delegates.
(c)
The economic studies are based on the assumption that the level of technology and available facilities and skills are equivalent to those presently available for building the equivalent steel ship.
Under these limitations the estimated comparative costs for building ten steel or GRP ships is approximately $12 500 000/ship in steel and from $15 000 0 0 0 -
PAPERS PRESEN TED
Catalysts and additives Lipiec, J. M. et al 'Toughness vs flexibility in epoxy resins' (l-A) Atkins, K. E. et al 'Vinyl polymers and ecaprolactone polymers as low profile additives' (l-B) Simmonds, J. and Roskott, L. 'Testing procedure for catalysts in polyester moulding' (l-C) Kolczynski, J. R. and Harpell, G. A. 'Mixed catalyst systems for increased productivity in mold curing of unsaturated polyesters' (l-D)
Resins - I Larsen, E. R. and Weaver, W. C. 'FR-1138 dibromoneopentyl glycol-based unsaturated polyesters: preparation and evaluation' (2-A)
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In the author's opinion the main message from the Conference was the need for more R and D into improved production methods in the fabrication of composite materials. This is certainly the present philosophy in the USA, and one which Europe must follow if it is to achieve an increasing share in this rapidly expanding market in composite materials.
Bradley, R. H. and Huminski, F. M. 'A new low-shrink polyester resin for color applications' (2-B) Pietsch, G. J. 'Cypor-1000 polyester resin for light weight casting' (2-C) Gibbs, H. H. 'Low void composites based on NR-150 polyimide binders' (2-D)
Reinforcements and fillers Jaxay, F. F. 'A new method of spinning glass fibres - a process for the consumer' (3-A) Bushman, E. F. 'Colored glass fibers, mats, papers and fabrics for decorative reinforced plastics, rubber, composites or coated fabrics review and forecast' (3-B)
McCorsley, C. C. 'Encron ® reinforcement of polyester laminates' (3-C) Ewchuk, W. 'Asbestos/ebonite composites' (3-D)
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Berger, S. E., Orenski, P. J. and Ranney, M. W. 'Silane coupling agents - performance in engineering plastics' (3-E) Milewski, J. V. 'A study of the packing of milled fiberglass and glass beads' (3-F) Ritter, J. R. 'Use of solid glass spheres in tooling resins' (3-G) Housing and construction McDermott, J. S. 'The meaning of performance concepts for plastics in construction' (4-A) Benjamin, B. S. 'Instant parachute plastics house for disaster areas' (4-B) Trampenau, R. H. and Evans, T. R. 'Fire retardant frp in construction' (4-C) Gerin-Lajoie, G. 'An architect's experience in frp building and housing construction' (4-D) Powell, D. 'New contributions of frp in the construction industry' (4-E) Bedell, D. W. 'How to use government agencies to sell new plastics building" products' (4-F)
COMPOSITES . S E P T E M B E R 1973
R e i n f o r c e d thermoplastics - I Maine, F. W. et al 'A new family of reinforced thermoplastics' (5-A) Broutman, L. J. and Agarwal, B. I). 'A theoretical, study of the effect of the interface on composite toughness' (5-B) Speri, W. M. and Jenkins, C.F. 'Effect of fiber-matrix adhesion on the properties of short fiber reinforced abs' (5-C) Mclnerney, E. G. and Thomas, D. P. 'Application of thermoplastics composites in major appliances' (5-D) Theberge, J. E. et al 'Gear and bearing design with lubricated and reinforced thermoplaStics' (5-E) Eickert, J. S. 'International applications of reinforced engineering thermoplastics' (5-F) Resins - H Gilbu, A. and Rolston, J. A. 'Design, production and testing of large diameter reinforced plastic underground effluent pipe' (6-A) Howard, A. K. and Selander, C. E. 'Laboratory load tests on buried reinforced thermosetting thermoplastics and steel pipe' (6-B) Pope, T. C. Jr 'Spirally wound fiber glass reinforced plastic pipe for condenser circulating water applications' (6-C) Minsker, J. H. and Triestram, D. E. 'Filament wound tankers using Derakane ® vinyl ester resins' (6-D) Meyer, L. S. and Eden, D. H. 'Corrosion resistant reinforced plastic grating by a unique imbedded pultrustion process' (6-E) Bathroom components Cravens, T. E. and Wolfe, W. 'Acrylic bathroom fixtures with reinforced syntactic foam backup' (7-A) Welsch, G. J. and Freygang, G. G. 'Second surface reinforced thermoformed acrylic parts; materials and procedures for manufacture' (7-B) Horner, A. H. and Church, S. L. 'Acrylicfaced bathroom equipment - design for performance!' (7-C) Connolly, W. J., Kerle, E. J. and Sprow, T. K. 'Filled polyester spray-up systems offering improved fire hazard classifications' (7-D) Seymour, M. 'Design research of a sheet molding compound tub/shower' (7-E) Research and d e v e l o p m e n t - I and H Carey, J. E. and Launikitis, B. M. 'Status report vinyl ester resins 1973' (8-A) Green, D. H. and Guevin, P. R. 'Polyurethanes - the new frp finish' (8-B) Cech, L. S. and Bretz, J. 'Formulation, preparation and molding of low-pressure polyester decorative laminates containing diacetone acrylamide' (8-C) McKenzie, F. M. 'Two component polyurethane finishes for plastic substrates (8-D) Bowerman, H. H. and McCarthy, W. J. 'High strain-rate testing of hycar cthn modified epoxy resins' (9-A) Chiao, T. T. and Marcon, M. A. 'Filamentwound vessel from an organic fiber epoxy system' (9-B) Robinson, E. Y. 'On the elastic properties of fiber composite laminates with statistically dispersed fiber and ply orientations' (9-C) Geiler, D. E. 'Analysis, test and comparison of composite material laminates configured for isotropic low-thermal-expansion' (9-D)
COMPOSITES. SEPTEMBER 1973
Price, H. L. 'Preparation and thermomechanical properties of pyrrone moldings' (9-E) Fujii, T., Fukuda, T. and Zako, M. 'Analysis of dynamical behaviour for composite materials' (9-F)
Occupational Health and S a f e t y A c t Panel discussion on Occupational Health and Safety Act: no papers in proceedings book (10) Corrosion control and fire resistance - I Menges, G., yon Harnier, A. and Heisse, P. 'Properties of carbon fiber reinforced polyimides in dependence of the manufacturing process' (1 l-A) Cameron, A. B., Heron, G. F. and Wicker, G.L. 'Asbestos reinforced thermoplastics' (11-B) Kietzman, J. H. and Axelson, J. W. 'Polyolefin composites: comparison of mineral fillers' ( 1 l-C) Wambach, A. D. and Kramer, M. 'Valcox ® 420-SEO - a glass-reintorced thermoplastic polyester with built-in flame retardance' (1 l-D) Rausch, K. W. Jr, Farrissey, W. J. Jr and A. A. R. Sayigh 'New thermoplastic polyimide for high temperature composites' (1 I-E) Marsden, J. G. and Pepe, E.J. 'Water soluble polymeric coupling agents' (1 l-F).
Vogelei, R. A. 'The Chevrolet Corvette twenty years of fiberglass reinforced plastic production!' (14-E) Gutette, R. S. 'Design and test of pickup truck box cover' (14-F)
A e r o s p a c e - 11 Browning, C. E. 'The effects of moisture on the properties of high performance structural resins and composites' (15-A) Chase, V. A. and van Auken, R. L. 'Feasibility evaluation of graphite/epoxy composite inaterials to helicopter transmission housing' (15-B) Wolkowitz, W. and Poveromo, L. M. 'The effect of long-time thermal exposure on the mechanical properties of graphite/ polyimide composites' (15-C) Hardesty, E. E. 'Advanced composites, the on-going transition from handmade prototypes to machine-fabricated components' (15-D) Cusamano, J., Huber, J. and Telford Marshall, K. 'Drilling high strength composites with ultrasonics' (15-E) Corrosion control and fire resistance - 111 Jones, B. H. 'A consideration of the strength and structural characteristics of filamentary composite pipe' (16-A) Greenwood, M. E. 'The investigation of axial strength of filament wound chemical tank laminates' (16-B) Belanger, G. 'Interlaminar sheardelamination-key factor in designing large frp tanks' (16-C) Anderson, T. F. and Baldwin, W. L. 'Effect of laminate construction on fire retardance and corrosion resistance of reinforced plastics structures' (16-D)
Aerospace - I van Auken, R. L. and Chase, V. A. 'Ballistic-tolerant helicopter flight control components from plastic composite materials' (12-A) Sturgeon, J. B. 'Fatigue and creep testing of unidirectional carbon fibre reinforced R e i n f o r c e d thermoplastics - H plastics' (12-B) Chamis, C. C., Hanson, M. P. and Serafini, T. T. Outwater, J. O. and Murphy, M. C. 'Tile toughness of reinforced plastics' (17-A) 'Criteria for selecting resin matrices for Broutman, L. J. and Rotem, A. 'Impact improved composite strength' (12-C) strength and fracture of carbon fiber comRobinson, E. Y. 'Acoustic emission studies posite beams' (17-B) of large advanced composite rocket motor Simon, R. A. 'Impact strengths of carbon cases' (12-D) fiber composites' (17-C) Leopold, P. M. and Arens, J. E. 'Design Herrick, J. W. 'Bearing materials from and application of high performance graphite fiber composites' (17-D) composites' (12-E) Vaughan, R. W., Jones, R. J. and Burns, E. A. 'High temperature creep properties of Corrosion control and fire resistance - H PlOP polyiamide-HMS graphite composites' Piegsa, J. G., Anderson, T. F. and Sams, L. L. (17-E) 'Monomer content vs corrosion resistance of vinyl ester resins' (13-A) S h e e t and bulk m o u l d i n g c o m p o u n d s Bernhoft, R. C. et al 'Quality control I and H for corrosion resistant equipment' (13-B) Lewandowski, R. J. and Longenecker, D. M. Clavadetscher, D. J., English, F. and 'Fire retardant frp in corrosion control: MacGill, T. 'New market applications in design and code criteria' (13-C) smc and bmc - demand precision molding Desai, R. R. 'Cossosion control fiber techniques' (18-A) reinforced plastic enclosures' (13-D) Luchini, A. 'New pigmented smc for the furniture industry' (18-B) Transportation Ring, E. 'SMC capabilities - a five year history at Goodyear Aerospace Corporation' Rosato, D. V. 'Cost comparison of plastic (18-C) parts for the transportation industry based on different manufacturing processes' Horton, A. S. 'Design of computer hous(14-A) ings with sheet molding compound' (18-D) Raschbichler, H. G. 'MBB's experience Selley, J. E., Shah, N. N. and Kay, D. J. 'Formulating fire retardant smc' (18-E) in the development and production of road-vehicles with a chassis of self-supporting Conley, D. O. 'Status of pigmented low plastic sandwich constructions' (14-B) shrink smc or bmc' (19-A) Scott, R. J. and Sommella, J. H. Kalnin, I. L. 'Graphite fiber reinforced 'Feasibility study of glass reinforced epoxy bulk molding compounds' (19-B) • plastic cargo ship' (14-C) Gott, S. L., Suggs, J. L. and Blount, W. W. Keown, J. A. 'SMC versatility in the 'New unsaturated polyester resins based design's construction of General Motors on TMPD ® Glycol for frp composites' '73 motor home' (14-D) (19-C)
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Austin, T. J., Tropp, F. E. and Pulman, L. J. 'Continuous metering and process control of sheet molding compound' (19-D) Warner, K. N. 'Mechanism of the thickening of polyesters by alkaline earth oxides and hydroxides' (19-E) Fekete, F. 'New and novel smc and bmc compounds' (19-F)
Marine and recreation Gray, E. Jr, Zion, E. M. and Richter, S. 'Joint configuration and surface preparation effect on bond joint fatigue in marine applications' (20-A) Hill, J. E. and Pearson, E.'A. 'Graphite fiber tow reinforcement in boat hull. construction' (20-B) Knutson, R.N. 'The growth of frp assembly' (20-C)
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Lindler, J. M., McLain, P. H., and Thomas, F.W. 'Composite sporting goods products' (20-D) Mayer, L. S. 'Advanced highly recurved reinforced plastic archery bows' (20-E)
The interface Deitz, V. R. and Brooks, E.J. 'Chemical reactivity of graphites in gas-solid systems' (21-A) Goan, L C., Martin, T. W. and Prescott, R. 'The influence of interfacialbonding on the properties of carbon fber composites' (21-B) Butler, B. L., LeMaistre, C. W. and Diefendorf, R. J. 'The structure of high modulus graphite fibers' (2 l-C) Lando, J. B. and Semen, J. 'Catalytic effects of graphite fiber surfaces in in situ matrix formation' (2 l-D)
Plueddemann, E. P. and Stark, G. L. 'Catalytic and electrostatic effects in bonding through silanes' (21-E)
Processing Sikes, S. 'A Material system for the mass production of reinforced plastic parts' (22-A) Thornton, A. M. Jr, K~auter, R. and Grannis, C. III 'Use of cold press molding to initiate a new product in the underground electrical power distribution field' (22-B) Maihart, H. H. and Reiter, R. H. 'Mass production of large silos and storage tanks in centrifugal casting technique' (22-C) Bauer, S. H. 'Fiber degradation in thermoset injection molding' (22-D) Ives, F. and MacDonell, R. 'Mechanized material handling and conversion of frp (the Lash Project)' (22-E)
COMPOSITES . S E P T E M B E R 1973
plastics -- ever new
28th SPI A n n u a l Conference
This year's Conference attracted some 2 000 delegates to hear at least some of the 100 papers given in 22 concurrent sessions during the four days of the meeting. This report tries to give an overall picture of the areas where research and development is most active, and which markets in composite materials currently appear most attractive in the USA. The conference covered 15 areas (see list of papers) and those areas which covered two or even three sessions are obviously the ones where companies consider that research and development will be most rewarding. Although there were specific sessions labelled 'Research and Development', every paper submitted involved either some research or development. The 'Research and Development' sessions, which will be dealt with first, tended to cover the more academic papers and were mostly submitted either by government laboratories, universities, or aviation laboratories. RESEARCH AND DEVELOPMENT
There has been a significant trend over recent years away from papers based purely or mainly on theoretical treatments of the behaviour of composite materials stressed in a variety of modes; although still largely based on a theoretical approach the papers tended to contain more experimental data for comparison with theory, and were directed to the more urgent areas where design data is necessary for expansion in the utilisation of composite materials. There seemed no doubt this year that the emotive term 'brittleness', or lack of toughness, is the main stumbling block to the increased use of high performance composites in highly stressed applications, especially in those areas where sudden failure could have catastrophic consequences. Much interest has been shown in the concept of toughening epoxide resins by the incorporation of rubber spherical particles, in particular the use of carboxyl terminated butadiene (ctbn) which, due to reaction between the carboxyl termination and the epoxide resin, results in good adhesion at the rubber sphere/resin interface. There is now good evidence that, using the 'in situ' formation of spheres of suitable diameter, ideally a bimodal distribution of spheres, some 1-5/am diameter, and others <1 000 A diameter, impressive improvements in fracture toughness and impact strength can be attained. No data were presented, however, on the improvements occasioned by the use of ctbn modified epoxide resins in composites, which was disappointing. Our own experience and the experience of others at the Conference was that the improvements achieved in the resin had not so far been realized in the composites. Papers on the toughness of composites were presented by Professor Outwater (17-A) and Professor Broutman
COMPOSITES. SEPTEMBER 1973
(17-B). The former's paper discussed the sources of energy dissipation during composite fracture and quantified these by considering the energetics of fibre debonding. Broutman's paper described experiments using an instrumented drop weight impact machine to measure the impact strength of carbon fibre composite. His findings, that increases in strength and energy absorption increase with increasing impact velocity, seem to agree with early results from work at Harwell by Hancox and Minty which involved the study of torsional impact at strain rates of up to 50 rad/s. Robert Simon (17-C) from the Naval Ordnance Laboratory made a plea for work on what he termed an 'energy threshold' to create damage in composites. His well written paper described the impacting of NOL carbon fibre composite rings and subsequent measuring of their residual compressive strength; a typical graph illustrating this threshold concept is shown in Fig. 1. His paper also illustrated that the incorporation of other high strength fibres of lower modulus, eg PRD 49, can uprate the threshold impact value of carbon fibre composites.
AEROSPACE AND HIGH PERFORMANCE COMPOSITES
Personally the most interesting paper in this session was that by E. E. Hardesty (15-D) of Goldsworthy Engineering Inc, a company well known in the rapidly expanding processing field known as 'pultrusion'. Conventionally pultruded composites are produced continuously in a wide variety of profiles such as rods, bars, tubes, box sectians, etc, and normally in straight lengths of up to 9 m (30 ft). Hardesty described Goldsworthy's latest innovation, equipment which will produce curved or circular composites again in a variety of profiles. A typical product is the production of large rings or hat sections for skin stiffening. This paper, and a later paper from the same organization dealing with the production of pultruded piping, emphasized
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the need for more effort in evolving processes for producing composites in a highly reprodticible and economic manner. The paper by Browning (15-A) of the Air Force Materials Laboratory, suggested that, whilst a variety of cast resin systems were not hydrolyticaUy unstable, water could act as a plasticizing agent and apparently disrupt the strong hydrogen bonding present in highly polar epoxide systems. As evidence, he tabled results which showed the reversability of the water absorption effect and the change in failure mode of dry and wet specimens. The results emphasized the need for more environmental studies allied to mechanical testing to produce more meaningful design data than that normally available at a single humidity or temperature. John Sturgeon (12-B) of RAE Farnborough presented a paper on the creep and fatigue of carbon composites in a tensile mode, which effectively indicated the excellent creep resistance in this mode; he did however point out a large variability in fatigue results which he attributed to the characteristics of the material. Other papers included acoustic emission studies on boron/ epoxide and graphite/epoxide composite rocket motor cases and the evaluation of graphite/epoxide composite materials for helicopter transmission housing. It is significant that an increasing number of papers on the high modulus fibres are now concerned with the manufacture of prototypes rather than purely devoted to testing techniques.
PROCESSING
Further illustrations of quickening interest in mass production or mechanization of processes for producing composite materials were papers by S. Sikes (22-A) of GRTL Company and H. H. Maihart and R. H. Reiter (22-C) of Kolosius GmbH Austria. Sikes' paper described the forming of swirl glass reinforced thermoplastic sheet on conventional metal stamping equipment. Cycles as short as 15-20 s are achievable where production volume affords automated feeding and part removal system. The Austrian paper was concerned with the economic and rapid production of large volume standing storage tanks. Basically the centrifugal casting equipment consists of a rotatable cylindrical mould which can achieve rotational speeds of 5 - 9 0 rpm which in the case of a 3½ m (11½ ft) diameter rotor would correspond to a maximum of 16 m/s (54 ft/s). The resin/glass depositor is fitted on a telescopic jib and other basic equipment includes supply tank, pump equipment, glass rovings stand, ancillary mechanical consolidation and the controls. There is an overhead travelling crane to enable the mould, which is split in the axial direction, to be opened for the removal of the completed tank. Production time for a silo of 99 m 3 (3 500 ft3), was given as 2% hours or approximately 3 silos/8 h shift. The author made a very good case for the choice of centrifugal method as opposed to filament winding techniques, which, due to higher glass fibre content, would give similar deflection with a thinner wall section and thus use less material.
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His argument was that in the specific cases if silos and similar storage tanks, the high mechanical strengths achieved by filament winding are unnecessary, because in the calculation for wall thickness, static inside pressure is less important than in resistance to deformation due to wind pressure and silo-handling. HOUSING AND CONSTRUCTION
An ingenious method for providing emergency accommodation in disaster areas used the concept of converting a flexible fabric parachute into a rigid shell in the time between release and hitting the ground. The imaginative paper by Professor Benjamin (4-B) of the School of Architecture at the University of Kansas covered in some detail the problems associated with such a concept; these were, briefly, choice of a suitable resin system, type of parachute and the fabric used to construct it, the opening characteristics, method of impregnation, aerodynamic behaviour and, a very important factor, the need for a visual leaflet to convey to possibly illiterate people the correct use of the shelter. David Powell (4-E) of Polyplan, England, gave a very professional paper on 'New Contributions of FRP in the Construction Industry': he described the large scale application of reinforced plastic cladding panels at the Southbrook Comprehensive School and the extensive use of such panels, 2 7871 m 2 (300 000 ft2), in a redevelopment scheme for HMS Raleigh, the shore-based training establishment of the Royal Navy. REINFORCED THERMOPLASTICS, SHEET MOULDING COMPOUNDS, AND DOUGH MOULDING COMPOUNDS
These materials are competitors for supplying probably the largest potential markets in reinforced plastics, eg.the Transportation Industry. Two years ago there seemed to be a swing to reinforced thermoplastics for the car industry, but the sheet moulding compound advocates have come back with improved properties and processes and are again strong contenders in the market. Undoubtedly cost will be the prime consideration in determining which material is t'mally chosen, but other factors, eg specific stiffness, creep and impact resistance, will also influence the choice. Although 23 papers were delivered on these materials, the author found only one which seemed novel. This was a paper by D. F. Maine (5-A) of Fibreglass Canada on the use of mica as a reinforcement for thermoplastics. Mica has, of course, been used in plastics for a considerable time, but normally as a high quality filler to improve electrical properties. Maine pointed out that polymers reinforced with platelets can be treated in a manner similar to discontinuous short fibres and that if one makes similar assumptions to those used in short fibre theories, eg good bonding, sufficient aspect ratio, good distribution, and uses mica with a modulus of 172 x 103 MN/m 2 (25 x 106 psi) and tensile strengths as high as 3 100 MN/m 2 (450 000 psi), a reinforced polymer superior to a similar short glass fibre filled polymer would result. He als~J suggested that due to the plate-like nature of mica the strengths measured would be more truly isotropic than fibres, and illustrated this by a graph (Fig.2) which compares the
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By using rods of various aspect ratios and spheres of various diameters in packing experiments, he derived graphs which should optimize the packing of spheres and fibres in a polymeric matrix. His paper will be very useful as a guide to anyone involved in such areas of development, eg Idled thermoplastics and thermosets, sheet and bulk moulding compounds, and is well worth studying.
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particular his work with ceramic whiskers as reinforcements of materials. His paper this year was on a more mundane level, namely a consideration of the packing efficiency of fibres and spheres.
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A joint paper given by J. E. Hill of Great Lakes Research Corp and E. A. Pearson of Tillotson-Pearson Inc (20-B) described the use of wide tow carbon fibre/resin reinforcements of selected areas of a 14 m (46 ft) glass fibre/balsa core sandwich sailing sloop. Construction details of the stern, backbone-keel support skeg, and stern areas, which are those reinforced by carbon fibre, ~vere given in reasonable detail and obviously much effort had been spent in design to ensure that the reinforcement was used efficiently and economically. Dramatic weight savings were achieved. The total weight of carbon fibre/resin composite used was 23 kg (50 lb)
The properties he listed for mica filled nylon included 17.2 x 103 MN/m 2 (2.5 x 106 psi) modulus with approaching 96 MN/m 2 (14 000 psi) tensile strength (not included in the preprint) of the reinforcing effects in thermoset resins; these implied that mica merits serious consideration as a reinforcement for many polymers.
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RESINS, REINFORCEMENTS AND FILLERS
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Work reported on resins is usually almost totally confined to either polyesters or epoxides, and normally concerns such aspects as improving fire or corrosion resistance, or the use of additives to give lower shrink characteristics in the case of polyesters; this year was no exception and, in my view, nothing startling emerged.
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The same usually applies to reinforcement but in recent years we have had reports of carbon and boron fibres and PRD 49. This year, American Enka Company reported work on the effects of using ENCRON polyester fibre reinforcement in composite materials.
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C. C. McCorsley (3-C) presented the paper, which examined improvements in abrasion resistance, chemical resistance, and impact, by using various types of sandwich construction with layers of glass or terylene reinforced polyester resin. As one would expect from theory the best combination of flexural strength, flexural modulus, and impact came from a combination of glass woven rovings on the tensile and compressive axis, with layers of terylene fabric in the neutral plane as shown in Fig.3. Many papers in the past have described the effect of adding short glass fibres to polymers, in particular in thermoplastics, and in recent years interest has quickened in the use of spherical glass to confer rigidity and dimensional stability in polymers. Dr J. Milewski (3-F) of Esso Research Engineering Co is well known in the USA for his work on ceramics and in
COMPOSITES. SEPTEMBER 1973
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compared to 104 kg (230 lb) of unidirectional glass/ resin composite which would be necessary to achieve the same stiffness.
$17 000 000/ship in grp using either a pessimistic or optimistic cost estimate.
The sloop Fantasia has now completed one year's sailing and is in excellent condition having weathered two severe storms in the 1972 Bermuda-Newport race.
BATHROOM COMPONENTS
It is interesting to compare the paper by R. J. Scott and J. H. Sommella (14-C), of Gibbs and Cox Inc, which is a feasibility study of large glass reinforced cargo boats, typically 137 m (450 ft) long with a wide beam of 21 m (69 ft) and displacing 16 764 tonnes (16 500 long tons).
At present in the USA the use of composites in bathroom components has probably the largest growth rate in the building and construction area. In particular the concept of vacuum forming thermoplastic sheet and subsequently rigidizing with glass/resin reinforcement, first reported by V. Staynor in 1970, has become a very popular and economic way of forming composite materials.
The work, sponsored by the Ship Structures Committee of the National Research Council, is very detailed, and the conclusions state that a ship of this size is perfectly feasible, but its durability is questionable and not economically justified in direct competition with a steel vessel of equivalent capabilities. Fire resistance is also given as a major drawback under current US Coast Guard regulations.
The papers this year were concerned with ways of automating and speeding the process and also with drawing attention to the superiority of the thermoplastic component over traditional gel-coats under impact conditions; this philosophy appears to make good sense especially when one considers that vacuum forming/rigidizing processes are spreading to a number of other applications, eg sailing dinghies, building cladding panels, etc.
When the limitations set on the study are considered, however, the future looks promising. These limitations included:
Unlike the British Plastics Federation Conference the SPI has no formal dosing speeches, the delegates depart and prepare for another marathon in twelve months time.
(a)
The ship would be constructed from state of the art materials: local stiffening using carbon fibre composites was precluded.
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Although the authors concede the possible development of a major breakthrough in fabrication of large GRP structures, they consider this will require a significant R and D effort requiring a great deal of time and money. They therefore assumed that hand lay-up technology would be used.
It is an exhausting Conference for participants, but is usually rewarding in spite of the normal quota of superficial and blatantly commercial papers. It is disappointing not to see more European delegates attending. Reading the rather bulky and lengthy reprints of the proceedings is a poor alternative to involvement in the sessions and discussions, and even more, out of session discussions with other delegates.
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The economic studies are based on the assumption that the level of technology and available facilities and skills are equivalent to those presently available for building the equivalent steel ship.
Under these limitations the estimated comparative costs for building ten steel or GRP ships is approximately $12 500 000/ship in steel and from $15 000 0 0 0 -
PAPERS PRESEN TED
Catalysts and additives Lipiec, J. M. et al 'Toughness vs flexibility in epoxy resins' (l-A) Atkins, K. E. et al 'Vinyl polymers and ecaprolactone polymers as low profile additives' (l-B) Simmonds, J. and Roskott, L. 'Testing procedure for catalysts in polyester moulding' (l-C) Kolczynski, J. R. and Harpell, G. A. 'Mixed catalyst systems for increased productivity in mold curing of unsaturated polyesters' (l-D)
Resins - I Larsen, E. R. and Weaver, W. C. 'FR-1138 dibromoneopentyl glycol-based unsaturated polyesters: preparation and evaluation' (2-A)
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In the author's opinion the main message from the Conference was the need for more R and D into improved production methods in the fabrication of composite materials. This is certainly the present philosophy in the USA, and one which Europe must follow if it is to achieve an increasing share in this rapidly expanding market in composite materials.
Bradley, R. H. and Huminski, F. M. 'A new low-shrink polyester resin for color applications' (2-B) Pietsch, G. J. 'Cypor-1000 polyester resin for light weight casting' (2-C) Gibbs, H. H. 'Low void composites based on NR-150 polyimide binders' (2-D)
Reinforcements and fillers Jaxay, F. F. 'A new method of spinning glass fibres - a process for the consumer' (3-A) Bushman, E. F. 'Colored glass fibers, mats, papers and fabrics for decorative reinforced plastics, rubber, composites or coated fabrics review and forecast' (3-B)
McCorsley, C. C. 'Encron ® reinforcement of polyester laminates' (3-C) Ewchuk, W. 'Asbestos/ebonite composites' (3-D)
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Berger, S. E., Orenski, P. J. and Ranney, M. W. 'Silane coupling agents - performance in engineering plastics' (3-E) Milewski, J. V. 'A study of the packing of milled fiberglass and glass beads' (3-F) Ritter, J. R. 'Use of solid glass spheres in tooling resins' (3-G) Housing and construction McDermott, J. S. 'The meaning of performance concepts for plastics in construction' (4-A) Benjamin, B. S. 'Instant parachute plastics house for disaster areas' (4-B) Trampenau, R. H. and Evans, T. R. 'Fire retardant frp in construction' (4-C) Gerin-Lajoie, G. 'An architect's experience in frp building and housing construction' (4-D) Powell, D. 'New contributions of frp in the construction industry' (4-E) Bedell, D. W. 'How to use government agencies to sell new plastics building" products' (4-F)
COMPOSITES . S E P T E M B E R 1973
R e i n f o r c e d thermoplastics - I Maine, F. W. et al 'A new family of reinforced thermoplastics' (5-A) Broutman, L. J. and Agarwal, B. I). 'A theoretical, study of the effect of the interface on composite toughness' (5-B) Speri, W. M. and Jenkins, C.F. 'Effect of fiber-matrix adhesion on the properties of short fiber reinforced abs' (5-C) Mclnerney, E. G. and Thomas, D. P. 'Application of thermoplastics composites in major appliances' (5-D) Theberge, J. E. et al 'Gear and bearing design with lubricated and reinforced thermoplaStics' (5-E) Eickert, J. S. 'International applications of reinforced engineering thermoplastics' (5-F) Resins - H Gilbu, A. and Rolston, J. A. 'Design, production and testing of large diameter reinforced plastic underground effluent pipe' (6-A) Howard, A. K. and Selander, C. E. 'Laboratory load tests on buried reinforced thermosetting thermoplastics and steel pipe' (6-B) Pope, T. C. Jr 'Spirally wound fiber glass reinforced plastic pipe for condenser circulating water applications' (6-C) Minsker, J. H. and Triestram, D. E. 'Filament wound tankers using Derakane ® vinyl ester resins' (6-D) Meyer, L. S. and Eden, D. H. 'Corrosion resistant reinforced plastic grating by a unique imbedded pultrustion process' (6-E) Bathroom components Cravens, T. E. and Wolfe, W. 'Acrylic bathroom fixtures with reinforced syntactic foam backup' (7-A) Welsch, G. J. and Freygang, G. G. 'Second surface reinforced thermoformed acrylic parts; materials and procedures for manufacture' (7-B) Horner, A. H. and Church, S. L. 'Acrylicfaced bathroom equipment - design for performance!' (7-C) Connolly, W. J., Kerle, E. J. and Sprow, T. K. 'Filled polyester spray-up systems offering improved fire hazard classifications' (7-D) Seymour, M. 'Design research of a sheet molding compound tub/shower' (7-E) Research and d e v e l o p m e n t - I and H Carey, J. E. and Launikitis, B. M. 'Status report vinyl ester resins 1973' (8-A) Green, D. H. and Guevin, P. R. 'Polyurethanes - the new frp finish' (8-B) Cech, L. S. and Bretz, J. 'Formulation, preparation and molding of low-pressure polyester decorative laminates containing diacetone acrylamide' (8-C) McKenzie, F. M. 'Two component polyurethane finishes for plastic substrates (8-D) Bowerman, H. H. and McCarthy, W. J. 'High strain-rate testing of hycar cthn modified epoxy resins' (9-A) Chiao, T. T. and Marcon, M. A. 'Filamentwound vessel from an organic fiber epoxy system' (9-B) Robinson, E. Y. 'On the elastic properties of fiber composite laminates with statistically dispersed fiber and ply orientations' (9-C) Geiler, D. E. 'Analysis, test and comparison of composite material laminates configured for isotropic low-thermal-expansion' (9-D)
COMPOSITES. SEPTEMBER 1973
Price, H. L. 'Preparation and thermomechanical properties of pyrrone moldings' (9-E) Fujii, T., Fukuda, T. and Zako, M. 'Analysis of dynamical behaviour for composite materials' (9-F)
Occupational Health and S a f e t y A c t Panel discussion on Occupational Health and Safety Act: no papers in proceedings book (10) Corrosion control and fire resistance - I Menges, G., yon Harnier, A. and Heisse, P. 'Properties of carbon fiber reinforced polyimides in dependence of the manufacturing process' (1 l-A) Cameron, A. B., Heron, G. F. and Wicker, G.L. 'Asbestos reinforced thermoplastics' (11-B) Kietzman, J. H. and Axelson, J. W. 'Polyolefin composites: comparison of mineral fillers' ( 1 l-C) Wambach, A. D. and Kramer, M. 'Valcox ® 420-SEO - a glass-reintorced thermoplastic polyester with built-in flame retardance' (1 l-D) Rausch, K. W. Jr, Farrissey, W. J. Jr and A. A. R. Sayigh 'New thermoplastic polyimide for high temperature composites' (1 I-E) Marsden, J. G. and Pepe, E.J. 'Water soluble polymeric coupling agents' (1 l-F).
Vogelei, R. A. 'The Chevrolet Corvette twenty years of fiberglass reinforced plastic production!' (14-E) Gutette, R. S. 'Design and test of pickup truck box cover' (14-F)
A e r o s p a c e - 11 Browning, C. E. 'The effects of moisture on the properties of high performance structural resins and composites' (15-A) Chase, V. A. and van Auken, R. L. 'Feasibility evaluation of graphite/epoxy composite inaterials to helicopter transmission housing' (15-B) Wolkowitz, W. and Poveromo, L. M. 'The effect of long-time thermal exposure on the mechanical properties of graphite/ polyimide composites' (15-C) Hardesty, E. E. 'Advanced composites, the on-going transition from handmade prototypes to machine-fabricated components' (15-D) Cusamano, J., Huber, J. and Telford Marshall, K. 'Drilling high strength composites with ultrasonics' (15-E) Corrosion control and fire resistance - 111 Jones, B. H. 'A consideration of the strength and structural characteristics of filamentary composite pipe' (16-A) Greenwood, M. E. 'The investigation of axial strength of filament wound chemical tank laminates' (16-B) Belanger, G. 'Interlaminar sheardelamination-key factor in designing large frp tanks' (16-C) Anderson, T. F. and Baldwin, W. L. 'Effect of laminate construction on fire retardance and corrosion resistance of reinforced plastics structures' (16-D)
Aerospace - I van Auken, R. L. and Chase, V. A. 'Ballistic-tolerant helicopter flight control components from plastic composite materials' (12-A) Sturgeon, J. B. 'Fatigue and creep testing of unidirectional carbon fibre reinforced R e i n f o r c e d thermoplastics - H plastics' (12-B) Chamis, C. C., Hanson, M. P. and Serafini, T. T. Outwater, J. O. and Murphy, M. C. 'Tile toughness of reinforced plastics' (17-A) 'Criteria for selecting resin matrices for Broutman, L. J. and Rotem, A. 'Impact improved composite strength' (12-C) strength and fracture of carbon fiber comRobinson, E. Y. 'Acoustic emission studies posite beams' (17-B) of large advanced composite rocket motor Simon, R. A. 'Impact strengths of carbon cases' (12-D) fiber composites' (17-C) Leopold, P. M. and Arens, J. E. 'Design Herrick, J. W. 'Bearing materials from and application of high performance graphite fiber composites' (17-D) composites' (12-E) Vaughan, R. W., Jones, R. J. and Burns, E. A. 'High temperature creep properties of Corrosion control and fire resistance - H PlOP polyiamide-HMS graphite composites' Piegsa, J. G., Anderson, T. F. and Sams, L. L. (17-E) 'Monomer content vs corrosion resistance of vinyl ester resins' (13-A) S h e e t and bulk m o u l d i n g c o m p o u n d s Bernhoft, R. C. et al 'Quality control I and H for corrosion resistant equipment' (13-B) Lewandowski, R. J. and Longenecker, D. M. Clavadetscher, D. J., English, F. and 'Fire retardant frp in corrosion control: MacGill, T. 'New market applications in design and code criteria' (13-C) smc and bmc - demand precision molding Desai, R. R. 'Cossosion control fiber techniques' (18-A) reinforced plastic enclosures' (13-D) Luchini, A. 'New pigmented smc for the furniture industry' (18-B) Transportation Ring, E. 'SMC capabilities - a five year history at Goodyear Aerospace Corporation' Rosato, D. V. 'Cost comparison of plastic (18-C) parts for the transportation industry based on different manufacturing processes' Horton, A. S. 'Design of computer hous(14-A) ings with sheet molding compound' (18-D) Raschbichler, H. G. 'MBB's experience Selley, J. E., Shah, N. N. and Kay, D. J. 'Formulating fire retardant smc' (18-E) in the development and production of road-vehicles with a chassis of self-supporting Conley, D. O. 'Status of pigmented low plastic sandwich constructions' (14-B) shrink smc or bmc' (19-A) Scott, R. J. and Sommella, J. H. Kalnin, I. L. 'Graphite fiber reinforced 'Feasibility study of glass reinforced epoxy bulk molding compounds' (19-B) • plastic cargo ship' (14-C) Gott, S. L., Suggs, J. L. and Blount, W. W. Keown, J. A. 'SMC versatility in the 'New unsaturated polyester resins based design's construction of General Motors on TMPD ® Glycol for frp composites' '73 motor home' (14-D) (19-C)
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Austin, T. J., Tropp, F. E. and Pulman, L. J. 'Continuous metering and process control of sheet molding compound' (19-D) Warner, K. N. 'Mechanism of the thickening of polyesters by alkaline earth oxides and hydroxides' (19-E) Fekete, F. 'New and novel smc and bmc compounds' (19-F)
Marine and recreation Gray, E. Jr, Zion, E. M. and Richter, S. 'Joint configuration and surface preparation effect on bond joint fatigue in marine applications' (20-A) Hill, J. E. and Pearson, E.'A. 'Graphite fiber tow reinforcement in boat hull. construction' (20-B) Knutson, R.N. 'The growth of frp assembly' (20-C)
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Lindler, J. M., McLain, P. H., and Thomas, F.W. 'Composite sporting goods products' (20-D) Mayer, L. S. 'Advanced highly recurved reinforced plastic archery bows' (20-E)
The interface Deitz, V. R. and Brooks, E.J. 'Chemical reactivity of graphites in gas-solid systems' (21-A) Goan, L C., Martin, T. W. and Prescott, R. 'The influence of interfacialbonding on the properties of carbon fber composites' (21-B) Butler, B. L., LeMaistre, C. W. and Diefendorf, R. J. 'The structure of high modulus graphite fibers' (2 l-C) Lando, J. B. and Semen, J. 'Catalytic effects of graphite fiber surfaces in in situ matrix formation' (2 l-D)
Plueddemann, E. P. and Stark, G. L. 'Catalytic and electrostatic effects in bonding through silanes' (21-E)
Processing Sikes, S. 'A Material system for the mass production of reinforced plastic parts' (22-A) Thornton, A. M. Jr, K~auter, R. and Grannis, C. III 'Use of cold press molding to initiate a new product in the underground electrical power distribution field' (22-B) Maihart, H. H. and Reiter, R. H. 'Mass production of large silos and storage tanks in centrifugal casting technique' (22-C) Bauer, S. H. 'Fiber degradation in thermoset injection molding' (22-D) Ives, F. and MacDonell, R. 'Mechanized material handling and conversion of frp (the Lash Project)' (22-E)
COMPOSITES . S E P T E M B E R 1973