Chopped strand mats

Fibrous Composites. These composites consist of fibers in a matrix. The fibers may be short or discontinuous and randomly arranged continuous filaments arranged parallel to each other in the form of woven rovings (coUections of bundles of continuous filaments) or braided (8). In the case of chopped strand mat the random arrangement is planar. In whisker (needle-shaped crystals or filaments of carbon and ceramics) reinforced materials the arrangement is usually three-dimensional and the resulting composites are macroscopically homogeneous. 

Fig. 5. Interlaminar fracture toughness, for a number of thermosetting and thermoplastic composites (36,37). Open white bars represent glass-fiber composites shaded bars are for carbon fibers. The materials are A, polyester (unidirectional) B, vinyl ester (CSM = chopped strand mat) C, epoxy (R/BR1424) D, epoxy (T300/914) E, PPS F, PES and G, PEEK. To convert J/m to fdbf/in. multiply by 2100.

This is a material produced from the impregnation of glass fibre-mat (fibreglass, which is in the form of dry sheet, is commonly known as chopped stranded mat (CSM)) or rovings, with a liquid and unsaturated polyester resin, which thickens chemically to a dry sheet form. The total mix is sandwiched between polyethylene films and then roller-pressed to impregnate and consolidate it. 

Chopped strand mat. This consists of chopped strands (bundles of glass filaments) about 2 in long bound togther by a resinous binder. This type of mat is used extensively in glass-reinforeed polyester struetures. 

Needle mat. This is similar to chopped strand mat except that the mat is held together by a loose stitching rather than a binder. 

A number of different binder materials are in use for chopped strand mat and include starch, polyvinyl acetate and polyesters. The binder used depends on the end use of the laminate and the method of fabrication. 

Furane resin-chopped strand mat laminates have tensile strengths in excess of 200001bf/in (140 MPa), a heat distortion temperature of about 218°C and good fire resistance. 

In order to get the best out of fibre reinforcement it is not uncommon to try to control within close limits the fibre content which will provide maximum stiffness for a fixed weight of matrix and fibres. In flexure it has been found that optimum stiffness is achieved when the volume fraction is 0.2 for chopped strand mat (CSM) and 0.37 for continuous fibre reinforcement. 

A very wide sheet of grp which is known to contain intrinsic defects 1 mm long, is subjected to a fluctuating stress which varies from 0 to 80 MN/m. How many cycles would the sheet be expected to withstand if it is made from (a) chopped strand mat (CSM) and (b) woven roving (WR) reinforcement. The crack growth parameters C and n, and the critical stress intensity factors, Kc, for these materials are... 

A sheet of chopped strand mat-reinforced polyester is 5 mm thick and 10 mm wide. If its modulus is 8 GN/m calculate its flexural stiffness when subjected to a point load of 200 N midway along a simply supported span of 300 mm. Compare this with the stiffness of a composite beam made up of two 2.5 mm thick layers of this reinforced material separated by a 10 mm thick core of foamed plastic with a modulus of 40 MN/m. ... 

Chopped Strand Mat This consists of strands of long chopped fibres deposited randomly in the form of a mat. The strands are held together by a resinous binder. 

Chondroitin 6-sulfate, 4 706 Chondroitin sulfates, 20 456 Chopped strand mat (CSM), 26 751 Chopper pumps, 21 78 Chop-stx number, for boron hydrides, 4 183 Chorinated trisodium phosphate, 4 52 Christmas tree module design, 15 835 Chromacity diagrams, 7 313-315 Chromaphores, 19 379 Chromate coatings, 9 827 Chromate conversion coatings, 16 218 Chromated copper arsenate, 3 276 ... 

ISO 2558 1974 Textile glass chopped-strand mats for reinforcement of plastics -Determination of time of dissolution of the binder in styrene ISO 3344 1997 Reinforcement products - Determination of moisture content... 

Intuitively, however, the RVE for an amorphous polymer may be expected to be no more than 10 nanometres or so. In an aligned fibre composite with continuous fibres we need to take a sample sufficiently large as to contain perhaps 30 to 50 fibres in a lateral dimension and in this case the coefficient of variation of stress as between fibres would enable a measure to be decided. In a random array of fibres however (chopped strand mat) the RVE must be of the order of a fibre length at least as is also the case for an aligned short fibre composite. 

A polyester resin P-43 (Rohm and Haas) was selected as a matrix material. The glass fiber reinforcement was in the form of a chopped strand mat (M 700) weighing 1 Vz oz/sq ft bonded together with a high solubility polyester resin. The chopped fibers were about 2 in. long and the fiber diameter was about 0.0004 in. 

Figure 51, Different types of glass fibers. (1) Continuous strand mat, (2) Surfacing mat, (3) Chopped-strand mat, (4) Woven roving). (Courtesy of Ownes Coming Fiberglass Corp.)...

Sheet molding compound (SMC), glass mat thermoplastics (GMT), chopped strand mat (CSM)... 

Rovings are rope-hke bundles of continnons untwisted strands for nse in snch processes as perform press molding, filament winding, spray-np, pnltmsion, and centrifugal casting. They can also be converted into chopped strand mats or cnt into short fibers for molding compounds. 

Although it might be expected that a combination of brittle reinforcing fibers and a brittle matrix (e.g., epoxy or polyester resins) would have low impact strength, this is not the case, and the impact strengths of the fibers or the matrix. For example, polyester composites with chopped-strand mat have impact strengths from 45 to 70 ft-lbf/in (94-147 kj/m ), whereas a typical impact strength for polyster resin is only about 1 ft-lbf/in (2.1 kj/m ). 

Franz T, Nurick GN, Perry MJ. Experimental investigation into the response of chopped strand mat glassfibre laminates to blast loading. Int J Impact Eng 2002 27 639-67. 

Property Unit Woven cloth Chopped strand mat Continuous roving... 

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