Лако-красочные материалы — производство

As shown in Table 6, the moisture content in the wood had a significant effect on the shear strength of wood-wood specimens (about 55%); whereas for phenolic FRP-wood speci­mens, there was a less significant influence of moisture content on the shear strength (about 6%). The average percent material (cohesive) failure for the wood-wood samples decreased by 29%, from about 81% for dry to 58% for wet. In contrast, the average percent material failures for the phenolic FRP-wood samples were about 81% for dry and 87% for wet, with a small increase of 7%. For the dry samples, the shear strength for wood-wood was 90% higher than for phenolic FRP-wood, while the percent material failures were nearly identical for both types of samples (about 81%). For the wet samples, the shear strength for wood — wood was 10% lower than for phenolic FRP-wood, but the percent material failure for wood-wood was 50% lower than for phenolic FRP-wood. The favorable results obtained for both dry and wet FRP-wood samples in relation to wood-wood samples is due mainly to the nature of the failure modes observed. The failure for the phenolic FRP-wood samples occurred primarily in the continuous strand mat layer of the FRP composite, and, therefore, the response of these samples was governed by the CSM in-plane or interlaminar shear strength, which is typically a relatively low value. Not only are the dry and wet shear strengths nearly identical for dry and wet phenolic FRP-wood samples, but the average value is close to the shear strength for wet wood-wood samples. This indicates that the interlaminar shear strength of the continuous strand mat is not affected much by moisture.