Open-hole compression

It is critical that surface treatment conditions be optimized to composite properties since overtreatment as well as undertreatment will degrade composite properties. Typically composite interlaminar shear strength (ILSS), in-plane shear, and transverse tension ate used to assess the effectiveness of surface treatment. More recently damage tolerance properties such as edge delamination strength, open hole compression, and compression after impact have become more important in evaluating the toughness of composite parts. 

Compressive strength after impact (MPa) Open-hole compressive strength (MPa) 332... 

As can be seen from the results, the composite formed from monomer/-polymer 114a with Celion G30-500 8HS fabric exhibited excellent mechanical properties [28], To a first approximation it would appear that the inherent fracture toughness of the matrix resin has been carried over to the composite panels. The CAI (compressive strength after impact) and OHC (open hole compression) tests are a direct measurements of the toughness of the composite part, the value of 332 MPa for the CAI compares very favorably to the value of 300 MPa typical for the thermoplastic composites. The OHC values under hot-wet test conditions would seem to indicate that the composite has very good retention of its mechanical properties at both 177°C and 203 °C. 

OHT open-hole tensile OHC open-hole compression CAI compression strength after impact EDS edge delamination strength. (Adapted from Table 4 in Pilato, L.A. Michno, M.J. Advanced Composite Materials Springer-Verlag Berlin, 1994 118.)... 

Soutis C. Modelhng the open hole compressive strength of composite laminates tested in hot-wet conditions. Plastics Rubber Compos 2009 38(2/3/4) 55—60. 

Potanova, M.A., Poc, C.C., Whitecomb, J.D. (1992). Open hole and post-impact compressive fatigue of stitched and unstitched carbon fiber-epoxy matrix composites. In Composite Materials Testing and Design (lOlh Volume), ASTM STP-1120 (G.C. Grimes ed.), ASTM, Philadelphia, PA, pp. 37-53. 

To put things in perspective, the effect of a hole on the tensile or compressive strength of a laminate is discussed here in more detail. This is the case of an open hole, that is, a hole that does not have a fastener in it. Such holes are... 

An improvement over the Whitney—Nuismer approach was that by Garbo and Ogonowski [21]. They solved the case of a fastener hole using complex elasticity and recovered the case of an open hole as a special case. They still use a characteristic distance as is done in the Whitney—Nuismer approach, but their method is applied to every single ply. In addition, it allows for any type of combined in-plane loading instead of uniaxial tension or compression. 

Soutis C, Fleck NA, Smith PA. Failure prediction technique for compression loaded carbon fibre-epoxy laminate with open holes. J Compos Mater 1991 25 1476-98. 

Gower MRL, Shaw RM. Assessment of the applicability of compression after impact (CAI) and open hole tension (OHT) methods for use under fatigue loading. In 13th European conference on composite material, Stockholm Sweden 2008. 

Figure 15.3 Composite damage due to fastener holes, (a) Tjfpical bolted junction between a composite wing skin and metallic connection (b) failure modes in a bolted joint under tension [6] and (c) compressive failure modes in a plate with an open hole.

Tensile strength at room temperature Uniaxial compression at room temperature Interlaminar shear at room temperature Open hole tension at room temperature (see Fig. 19)... 

Table 4.2 summarises some basic properties of PEEK-based APC2 thermoplastic composites from Cytec. The properties of finished components can be tailored by controlling fibre orientation during the layup process. Eull characterisation of a thermoplastic composite will include measurement of in-plane shear properties, open hole tensile and compressive failure, interlaminar fracture toughness and compression after impact. Cytec also produces TPC based on PEKK [20]. 

Much higher shear forces than in stirred vessels can arise if the particles move into the gas-liquid boundary layer. For the roughly estimation of stress in bubble columns the Eq. (29) with the compression power, Eq. (10), can be used. The constant G is dependent on the particle system. The comparison of results of bubble columns with those from stirred vessel leads to G = > 1.35 for the floccular particle systems (see Sect. 6.3.6, Fig. 17) and for a water/kerosene emulsion (see Yoshida and Yamada [73]) to G =2.3. The value for the floe system was found mainly for hole gas distributors with hole diameters of dL = 0.2-2 mm, opening area AJA = dJ DY = (0.9... 80) 10 and filled heights of H = 0.4-2.1 m (see Fig. 15). 

Compressed air may be used to keep hole open as casing partially withdrawn... 

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