Abstract
由於複合材料結構件，有質量輕和比強度高的特點，所以受到航太工業的青睞，但是複合材料對衝擊所造成的損傷卻很敏感，有時外表沒見到什麼損傷，但其機械性質已降低；再加上結構件在運輸安裝時，常會受到側向的扭矩，所以本文則針對這二個重要的因素－衝擊和預扭，探討它們對擬均向碳纖維/環氧樹脂複合材料疲勞性質的影響。我們先進行預扭和衝擊的殘餘強度試驗和疲勞試驗，來瞭解單一因素對複合材料積層板的影響，由其最後的破壞型態，可知受預扭的積層板，靜態破壞集中在試片二端，疲勞損傷則遍佈整根試片，而受衝擊的積層板，損傷均集中在衝擊處，由此可清楚知道它們對積層板的影響是完全不同的。預扭和衝擊的作用順序，對複合材料積層板的疲勞壽命和破壞型態也有明顯的差異，尤其是在低的負荷作用時，衝擊前的預扭會改變積層板的結構，使得壽命有增長的趨勢，且因衝擊時積層板的狀況不同，所以其最後的破壞型態，也有截然不同的現象。若在有預扭的疲勞試驗中，改變衝擊作用的時間，則可發現經過5000週次和經過10000週次再衝擊，所造成的影響差別不大，但若與預扭後直接衝擊的狀況比較，可發現在高的作用負荷下，先作用一些週次再衝擊，會使的疲勞壽命降低，但隨著作用負荷減少，兩者的差異就變小了。It is well known that fatigue loading can induce damage incomposite laminates, this damage accumulates with cycles andthen failure occures when some critical level of damage isexceeded.Low-velocity impact induces internal damage in thelaminate without any visible sign on the impacted or backsurface, but it results in a loss of laminate strength. Alsothe structure often subject to a pretorsion during fatigueloading, the torsion loading may result in matrix damagebetween laminates. In this paper fatigue behavior of carbon/epoxy composites under impact and pretorsional effects isconsidered. The sequence of impact and pretorsion changed tostudy their effects on the life of the composite materials.Theresult with impact first and then pretorsion, the fatigue lifeis shorter than that only after pretorsion and that only withimpact. But with pretorsion first and then impact it leads toquite different result. The curve seems to have no relation tothat only after impact and that only with pretorsion. If somecyclic loading with pretorsion is applied first and thenimpact, the fatigue life doesn't have clear different between5000 and 10000 cycles. But the fatigue life is shorter thanthat pretorsion first and then impact direstly.