212 Mechanics of Composite Materials,Second Edition composite is detrimental to its mechanical properties.These detriments include lower Shear stiffness and strength Compressive strengths Transverse tensile strengths 。Fatigue resistance ·Moisture resistance A decrease of 2 to 10%in the preceding matrix-dominated properties gen- erally takes place with every 1%increase in the void content.! For composites with a certain volume of voids V,the volume fraction of voids V,is defined as (3.11) Then,the total volume of a composite (v)with voids is given by 0c=0r十0m十0 (3.12) By definition of the experimental density Pe of a composite,the actual volume of the composite is (3.13) Pce and,by the definition of the theoretical density Par of the composite,the theoretical volume of the composite is 巡 0f+0m= (3.14) Pa Then,substituting the preceding expressions(3.13)and (3.14)in Equation (3.12), 0=0+0, Pae Pa The volume of void is given by 2006 by Taylor Francis Group,LLC212 Mechanics of Composite Materials, Second Edition composite is detrimental to its mechanical properties. These detriments include lower • Shear stiffness and strength • Compressive strengths • Transverse tensile strengths • Fatigue resistance • Moisture resistance A decrease of 2 to 10% in the preceding matrix-dominated properties gen￾erally takes place with every 1% increase in the void content.1 For composites with a certain volume of voids Vv the volume fraction of voids Vv is defined as (3.11) Then, the total volume of a composite (vc) with voids is given by (3.12) By definition of the experimental density ρce of a composite, the actual volume of the composite is (3.13) and, by the definition of the theoretical density ρct of the composite, the theoretical volume of the composite is (3.14) Then, substituting the preceding expressions (3.13) and (3.14) in Equation (3.12), . The volume of void is given by V v v v v c = . v v c f = + vm + vv. v w c c ce = ρ , v v w f m c ct + = ρ . w w v c ce c ct v ρ ρ = + 1343_book.fm Page 212 Tuesday, September 27, 2005 11:53 AM © 2006 by Taylor & Francis Group, LLC